| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH) |
| * |
| * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| * |
| * Interactivity improvements by Mike Galbraith |
| * (C) 2007 Mike Galbraith <efault@gmx.de> |
| * |
| * Various enhancements by Dmitry Adamushko. |
| * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com> |
| * |
| * Group scheduling enhancements by Srivatsa Vaddagiri |
| * Copyright IBM Corporation, 2007 |
| * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> |
| * |
| * Scaled math optimizations by Thomas Gleixner |
| * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de> |
| * |
| * Adaptive scheduling granularity, math enhancements by Peter Zijlstra |
| * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra |
| */ |
| #include "sched.h" |
| |
| #include <trace/events/sched.h> |
| |
| /* |
| * Targeted preemption latency for CPU-bound tasks: |
| * |
| * NOTE: this latency value is not the same as the concept of |
| * 'timeslice length' - timeslices in CFS are of variable length |
| * and have no persistent notion like in traditional, time-slice |
| * based scheduling concepts. |
| * |
| * (to see the precise effective timeslice length of your workload, |
| * run vmstat and monitor the context-switches (cs) field) |
| * |
| * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) |
| */ |
| unsigned int sysctl_sched_latency = 6000000ULL; |
| static unsigned int normalized_sysctl_sched_latency = 6000000ULL; |
| |
| /* |
| * The initial- and re-scaling of tunables is configurable |
| * |
| * Options are: |
| * |
| * SCHED_TUNABLESCALING_NONE - unscaled, always *1 |
| * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) |
| * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus |
| * |
| * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) |
| */ |
| enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG; |
| |
| /* |
| * Minimal preemption granularity for CPU-bound tasks: |
| * |
| * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) |
| */ |
| unsigned int sysctl_sched_min_granularity = 750000ULL; |
| static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; |
| |
| /* |
| * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity |
| */ |
| static unsigned int sched_nr_latency = 8; |
| |
| /* |
| * After fork, child runs first. If set to 0 (default) then |
| * parent will (try to) run first. |
| */ |
| unsigned int sysctl_sched_child_runs_first __read_mostly; |
| |
| /* |
| * SCHED_OTHER wake-up granularity. |
| * |
| * This option delays the preemption effects of decoupled workloads |
| * and reduces their over-scheduling. Synchronous workloads will still |
| * have immediate wakeup/sleep latencies. |
| * |
| * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) |
| */ |
| unsigned int sysctl_sched_wakeup_granularity = 1000000UL; |
| static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; |
| |
| const_debug unsigned int sysctl_sched_migration_cost = 500000UL; |
| |
| #ifdef CONFIG_SMP |
| /* |
| * For asym packing, by default the lower numbered CPU has higher priority. |
| */ |
| int __weak arch_asym_cpu_priority(int cpu) |
| { |
| return -cpu; |
| } |
| |
| /* |
| * The margin used when comparing utilization with CPU capacity. |
| * |
| * (default: ~20%) |
| */ |
| #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024) |
| |
| #endif |
| |
| #ifdef CONFIG_CFS_BANDWIDTH |
| /* |
| * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool |
| * each time a cfs_rq requests quota. |
| * |
| * Note: in the case that the slice exceeds the runtime remaining (either due |
| * to consumption or the quota being specified to be smaller than the slice) |
| * we will always only issue the remaining available time. |
| * |
| * (default: 5 msec, units: microseconds) |
| */ |
| unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; |
| #endif |
| |
| static inline void update_load_add(struct load_weight *lw, unsigned long inc) |
| { |
| lw->weight += inc; |
| lw->inv_weight = 0; |
| } |
| |
| static inline void update_load_sub(struct load_weight *lw, unsigned long dec) |
| { |
| lw->weight -= dec; |
| lw->inv_weight = 0; |
| } |
| |
| static inline void update_load_set(struct load_weight *lw, unsigned long w) |
| { |
| lw->weight = w; |
| lw->inv_weight = 0; |
| } |
| |
| /* |
| * Increase the granularity value when there are more CPUs, |
| * because with more CPUs the 'effective latency' as visible |
| * to users decreases. But the relationship is not linear, |
| * so pick a second-best guess by going with the log2 of the |
| * number of CPUs. |
| * |
| * This idea comes from the SD scheduler of Con Kolivas: |
| */ |
| static unsigned int get_update_sysctl_factor(void) |
| { |
| unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8); |
| unsigned int factor; |
| |
| switch (sysctl_sched_tunable_scaling) { |
| case SCHED_TUNABLESCALING_NONE: |
| factor = 1; |
| break; |
| case SCHED_TUNABLESCALING_LINEAR: |
| factor = cpus; |
| break; |
| case SCHED_TUNABLESCALING_LOG: |
| default: |
| factor = 1 + ilog2(cpus); |
| break; |
| } |
| |
| return factor; |
| } |
| |
| static void update_sysctl(void) |
| { |
| unsigned int factor = get_update_sysctl_factor(); |
| |
| #define SET_SYSCTL(name) \ |
| (sysctl_##name = (factor) * normalized_sysctl_##name) |
| SET_SYSCTL(sched_min_granularity); |
| SET_SYSCTL(sched_latency); |
| SET_SYSCTL(sched_wakeup_granularity); |
| #undef SET_SYSCTL |
| } |
| |
| void sched_init_granularity(void) |
| { |
| update_sysctl(); |
| } |
| |
| #define WMULT_CONST (~0U) |
| #define WMULT_SHIFT 32 |
| |
| static void __update_inv_weight(struct load_weight *lw) |
| { |
| unsigned long w; |
| |
| if (likely(lw->inv_weight)) |
| return; |
| |
| w = scale_load_down(lw->weight); |
| |
| if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) |
| lw->inv_weight = 1; |
| else if (unlikely(!w)) |
| lw->inv_weight = WMULT_CONST; |
| else |
| lw->inv_weight = WMULT_CONST / w; |
| } |
| |
| /* |
| * delta_exec * weight / lw.weight |
| * OR |
| * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT |
| * |
| * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case |
| * we're guaranteed shift stays positive because inv_weight is guaranteed to |
| * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22. |
| * |
| * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus |
| * weight/lw.weight <= 1, and therefore our shift will also be positive. |
| */ |
| static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw) |
| { |
| u64 fact = scale_load_down(weight); |
| int shift = WMULT_SHIFT; |
| |
| __update_inv_weight(lw); |
| |
| if (unlikely(fact >> 32)) { |
| while (fact >> 32) { |
| fact >>= 1; |
| shift--; |
| } |
| } |
| |
| fact = mul_u32_u32(fact, lw->inv_weight); |
| |
| while (fact >> 32) { |
| fact >>= 1; |
| shift--; |
| } |
| |
| return mul_u64_u32_shr(delta_exec, fact, shift); |
| } |
| |
| |
| const struct sched_class fair_sched_class; |
| |
| /************************************************************** |
| * CFS operations on generic schedulable entities: |
| */ |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| static inline struct task_struct *task_of(struct sched_entity *se) |
| { |
| SCHED_WARN_ON(!entity_is_task(se)); |
| return container_of(se, struct task_struct, se); |
| } |
| |
| /* Walk up scheduling entities hierarchy */ |
| #define for_each_sched_entity(se) \ |
| for (; se; se = se->parent) |
| |
| static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) |
| { |
| return p->se.cfs_rq; |
| } |
| |
| /* runqueue on which this entity is (to be) queued */ |
| static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) |
| { |
| return se->cfs_rq; |
| } |
| |
| /* runqueue "owned" by this group */ |
| static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) |
| { |
| return grp->my_q; |
| } |
| |
| static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len) |
| { |
| if (!path) |
| return; |
| |
| if (cfs_rq && task_group_is_autogroup(cfs_rq->tg)) |
| autogroup_path(cfs_rq->tg, path, len); |
| else if (cfs_rq && cfs_rq->tg->css.cgroup) |
| cgroup_path(cfs_rq->tg->css.cgroup, path, len); |
| else |
| strlcpy(path, "(null)", len); |
| } |
| |
| static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| struct rq *rq = rq_of(cfs_rq); |
| int cpu = cpu_of(rq); |
| |
| if (cfs_rq->on_list) |
| return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list; |
| |
| cfs_rq->on_list = 1; |
| |
| /* |
| * Ensure we either appear before our parent (if already |
| * enqueued) or force our parent to appear after us when it is |
| * enqueued. The fact that we always enqueue bottom-up |
| * reduces this to two cases and a special case for the root |
| * cfs_rq. Furthermore, it also means that we will always reset |
| * tmp_alone_branch either when the branch is connected |
| * to a tree or when we reach the top of the tree |
| */ |
| if (cfs_rq->tg->parent && |
| cfs_rq->tg->parent->cfs_rq[cpu]->on_list) { |
| /* |
| * If parent is already on the list, we add the child |
| * just before. Thanks to circular linked property of |
| * the list, this means to put the child at the tail |
| * of the list that starts by parent. |
| */ |
| list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, |
| &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list)); |
| /* |
| * The branch is now connected to its tree so we can |
| * reset tmp_alone_branch to the beginning of the |
| * list. |
| */ |
| rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; |
| return true; |
| } |
| |
| if (!cfs_rq->tg->parent) { |
| /* |
| * cfs rq without parent should be put |
| * at the tail of the list. |
| */ |
| list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, |
| &rq->leaf_cfs_rq_list); |
| /* |
| * We have reach the top of a tree so we can reset |
| * tmp_alone_branch to the beginning of the list. |
| */ |
| rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; |
| return true; |
| } |
| |
| /* |
| * The parent has not already been added so we want to |
| * make sure that it will be put after us. |
| * tmp_alone_branch points to the begin of the branch |
| * where we will add parent. |
| */ |
| list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch); |
| /* |
| * update tmp_alone_branch to points to the new begin |
| * of the branch |
| */ |
| rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list; |
| return false; |
| } |
| |
| static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| if (cfs_rq->on_list) { |
| struct rq *rq = rq_of(cfs_rq); |
| |
| /* |
| * With cfs_rq being unthrottled/throttled during an enqueue, |
| * it can happen the tmp_alone_branch points the a leaf that |
| * we finally want to del. In this case, tmp_alone_branch moves |
| * to the prev element but it will point to rq->leaf_cfs_rq_list |
| * at the end of the enqueue. |
| */ |
| if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list) |
| rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev; |
| |
| list_del_rcu(&cfs_rq->leaf_cfs_rq_list); |
| cfs_rq->on_list = 0; |
| } |
| } |
| |
| static inline void assert_list_leaf_cfs_rq(struct rq *rq) |
| { |
| SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list); |
| } |
| |
| /* Iterate thr' all leaf cfs_rq's on a runqueue */ |
| #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \ |
| list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \ |
| leaf_cfs_rq_list) |
| |
| /* Do the two (enqueued) entities belong to the same group ? */ |
| static inline struct cfs_rq * |
| is_same_group(struct sched_entity *se, struct sched_entity *pse) |
| { |
| if (se->cfs_rq == pse->cfs_rq) |
| return se->cfs_rq; |
| |
| return NULL; |
| } |
| |
| static inline struct sched_entity *parent_entity(struct sched_entity *se) |
| { |
| return se->parent; |
| } |
| |
| static void |
| find_matching_se(struct sched_entity **se, struct sched_entity **pse) |
| { |
| int se_depth, pse_depth; |
| |
| /* |
| * preemption test can be made between sibling entities who are in the |
| * same cfs_rq i.e who have a common parent. Walk up the hierarchy of |
| * both tasks until we find their ancestors who are siblings of common |
| * parent. |
| */ |
| |
| /* First walk up until both entities are at same depth */ |
| se_depth = (*se)->depth; |
| pse_depth = (*pse)->depth; |
| |
| while (se_depth > pse_depth) { |
| se_depth--; |
| *se = parent_entity(*se); |
| } |
| |
| while (pse_depth > se_depth) { |
| pse_depth--; |
| *pse = parent_entity(*pse); |
| } |
| |
| while (!is_same_group(*se, *pse)) { |
| *se = parent_entity(*se); |
| *pse = parent_entity(*pse); |
| } |
| } |
| |
| #else /* !CONFIG_FAIR_GROUP_SCHED */ |
| |
| static inline struct task_struct *task_of(struct sched_entity *se) |
| { |
| return container_of(se, struct task_struct, se); |
| } |
| |
| #define for_each_sched_entity(se) \ |
| for (; se; se = NULL) |
| |
| static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) |
| { |
| return &task_rq(p)->cfs; |
| } |
| |
| static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) |
| { |
| struct task_struct *p = task_of(se); |
| struct rq *rq = task_rq(p); |
| |
| return &rq->cfs; |
| } |
| |
| /* runqueue "owned" by this group */ |
| static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) |
| { |
| return NULL; |
| } |
| |
| static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len) |
| { |
| if (path) |
| strlcpy(path, "(null)", len); |
| } |
| |
| static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| return true; |
| } |
| |
| static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| } |
| |
| static inline void assert_list_leaf_cfs_rq(struct rq *rq) |
| { |
| } |
| |
| #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \ |
| for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos) |
| |
| static inline struct sched_entity *parent_entity(struct sched_entity *se) |
| { |
| return NULL; |
| } |
| |
| static inline void |
| find_matching_se(struct sched_entity **se, struct sched_entity **pse) |
| { |
| } |
| |
| #endif /* CONFIG_FAIR_GROUP_SCHED */ |
| |
| static __always_inline |
| void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec); |
| |
| /************************************************************** |
| * Scheduling class tree data structure manipulation methods: |
| */ |
| |
| static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) |
| { |
| s64 delta = (s64)(vruntime - max_vruntime); |
| if (delta > 0) |
| max_vruntime = vruntime; |
| |
| return max_vruntime; |
| } |
| |
| static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) |
| { |
| s64 delta = (s64)(vruntime - min_vruntime); |
| if (delta < 0) |
| min_vruntime = vruntime; |
| |
| return min_vruntime; |
| } |
| |
| static inline int entity_before(struct sched_entity *a, |
| struct sched_entity *b) |
| { |
| return (s64)(a->vruntime - b->vruntime) < 0; |
| } |
| |
| static void update_min_vruntime(struct cfs_rq *cfs_rq) |
| { |
| struct sched_entity *curr = cfs_rq->curr; |
| struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline); |
| |
| u64 vruntime = cfs_rq->min_vruntime; |
| |
| if (curr) { |
| if (curr->on_rq) |
| vruntime = curr->vruntime; |
| else |
| curr = NULL; |
| } |
| |
| if (leftmost) { /* non-empty tree */ |
| struct sched_entity *se; |
| se = rb_entry(leftmost, struct sched_entity, run_node); |
| |
| if (!curr) |
| vruntime = se->vruntime; |
| else |
| vruntime = min_vruntime(vruntime, se->vruntime); |
| } |
| |
| /* ensure we never gain time by being placed backwards. */ |
| cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); |
| #ifndef CONFIG_64BIT |
| smp_wmb(); |
| cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; |
| #endif |
| } |
| |
| /* |
| * Enqueue an entity into the rb-tree: |
| */ |
| static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node; |
| struct rb_node *parent = NULL; |
| struct sched_entity *entry; |
| bool leftmost = true; |
| |
| /* |
| * Find the right place in the rbtree: |
| */ |
| while (*link) { |
| parent = *link; |
| entry = rb_entry(parent, struct sched_entity, run_node); |
| /* |
| * We dont care about collisions. Nodes with |
| * the same key stay together. |
| */ |
| if (entity_before(se, entry)) { |
| link = &parent->rb_left; |
| } else { |
| link = &parent->rb_right; |
| leftmost = false; |
| } |
| } |
| |
| rb_link_node(&se->run_node, parent, link); |
| rb_insert_color_cached(&se->run_node, |
| &cfs_rq->tasks_timeline, leftmost); |
| } |
| |
| static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline); |
| } |
| |
| struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) |
| { |
| struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline); |
| |
| if (!left) |
| return NULL; |
| |
| return rb_entry(left, struct sched_entity, run_node); |
| } |
| |
| static struct sched_entity *__pick_next_entity(struct sched_entity *se) |
| { |
| struct rb_node *next = rb_next(&se->run_node); |
| |
| if (!next) |
| return NULL; |
| |
| return rb_entry(next, struct sched_entity, run_node); |
| } |
| |
| #ifdef CONFIG_SCHED_DEBUG |
| struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) |
| { |
| struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root); |
| |
| if (!last) |
| return NULL; |
| |
| return rb_entry(last, struct sched_entity, run_node); |
| } |
| |
| /************************************************************** |
| * Scheduling class statistics methods: |
| */ |
| |
| int sched_proc_update_handler(struct ctl_table *table, int write, |
| void __user *buffer, size_t *lenp, |
| loff_t *ppos) |
| { |
| int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
| unsigned int factor = get_update_sysctl_factor(); |
| |
| if (ret || !write) |
| return ret; |
| |
| sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, |
| sysctl_sched_min_granularity); |
| |
| #define WRT_SYSCTL(name) \ |
| (normalized_sysctl_##name = sysctl_##name / (factor)) |
| WRT_SYSCTL(sched_min_granularity); |
| WRT_SYSCTL(sched_latency); |
| WRT_SYSCTL(sched_wakeup_granularity); |
| #undef WRT_SYSCTL |
| |
| return 0; |
| } |
| #endif |
| |
| /* |
| * delta /= w |
| */ |
| static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se) |
| { |
| if (unlikely(se->load.weight != NICE_0_LOAD)) |
| delta = __calc_delta(delta, NICE_0_LOAD, &se->load); |
| |
| return delta; |
| } |
| |
| /* |
| * The idea is to set a period in which each task runs once. |
| * |
| * When there are too many tasks (sched_nr_latency) we have to stretch |
| * this period because otherwise the slices get too small. |
| * |
| * p = (nr <= nl) ? l : l*nr/nl |
| */ |
| static u64 __sched_period(unsigned long nr_running) |
| { |
| if (unlikely(nr_running > sched_nr_latency)) |
| return nr_running * sysctl_sched_min_granularity; |
| else |
| return sysctl_sched_latency; |
| } |
| |
| /* |
| * We calculate the wall-time slice from the period by taking a part |
| * proportional to the weight. |
| * |
| * s = p*P[w/rw] |
| */ |
| static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); |
| |
| for_each_sched_entity(se) { |
| struct load_weight *load; |
| struct load_weight lw; |
| |
| cfs_rq = cfs_rq_of(se); |
| load = &cfs_rq->load; |
| |
| if (unlikely(!se->on_rq)) { |
| lw = cfs_rq->load; |
| |
| update_load_add(&lw, se->load.weight); |
| load = &lw; |
| } |
| slice = __calc_delta(slice, se->load.weight, load); |
| } |
| return slice; |
| } |
| |
| /* |
| * We calculate the vruntime slice of a to-be-inserted task. |
| * |
| * vs = s/w |
| */ |
| static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| return calc_delta_fair(sched_slice(cfs_rq, se), se); |
| } |
| |
| #include "pelt.h" |
| #ifdef CONFIG_SMP |
| |
| static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu); |
| static unsigned long task_h_load(struct task_struct *p); |
| static unsigned long capacity_of(int cpu); |
| |
| /* Give new sched_entity start runnable values to heavy its load in infant time */ |
| void init_entity_runnable_average(struct sched_entity *se) |
| { |
| struct sched_avg *sa = &se->avg; |
| |
| memset(sa, 0, sizeof(*sa)); |
| |
| /* |
| * Tasks are initialized with full load to be seen as heavy tasks until |
| * they get a chance to stabilize to their real load level. |
| * Group entities are initialized with zero load to reflect the fact that |
| * nothing has been attached to the task group yet. |
| */ |
| if (entity_is_task(se)) |
| sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight); |
| |
| se->runnable_weight = se->load.weight; |
| |
| /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ |
| } |
| |
| static void attach_entity_cfs_rq(struct sched_entity *se); |
| |
| /* |
| * With new tasks being created, their initial util_avgs are extrapolated |
| * based on the cfs_rq's current util_avg: |
| * |
| * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight |
| * |
| * However, in many cases, the above util_avg does not give a desired |
| * value. Moreover, the sum of the util_avgs may be divergent, such |
| * as when the series is a harmonic series. |
| * |
| * To solve this problem, we also cap the util_avg of successive tasks to |
| * only 1/2 of the left utilization budget: |
| * |
| * util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n |
| * |
| * where n denotes the nth task and cpu_scale the CPU capacity. |
| * |
| * For example, for a CPU with 1024 of capacity, a simplest series from |
| * the beginning would be like: |
| * |
| * task util_avg: 512, 256, 128, 64, 32, 16, 8, ... |
| * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ... |
| * |
| * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap) |
| * if util_avg > util_avg_cap. |
| */ |
| void post_init_entity_util_avg(struct task_struct *p) |
| { |
| struct sched_entity *se = &p->se; |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| struct sched_avg *sa = &se->avg; |
| long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq))); |
| long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2; |
| |
| if (cap > 0) { |
| if (cfs_rq->avg.util_avg != 0) { |
| sa->util_avg = cfs_rq->avg.util_avg * se->load.weight; |
| sa->util_avg /= (cfs_rq->avg.load_avg + 1); |
| |
| if (sa->util_avg > cap) |
| sa->util_avg = cap; |
| } else { |
| sa->util_avg = cap; |
| } |
| } |
| |
| if (p->sched_class != &fair_sched_class) { |
| /* |
| * For !fair tasks do: |
| * |
| update_cfs_rq_load_avg(now, cfs_rq); |
| attach_entity_load_avg(cfs_rq, se); |
| switched_from_fair(rq, p); |
| * |
| * such that the next switched_to_fair() has the |
| * expected state. |
| */ |
| se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq); |
| return; |
| } |
| |
| attach_entity_cfs_rq(se); |
| } |
| |
| #else /* !CONFIG_SMP */ |
| void init_entity_runnable_average(struct sched_entity *se) |
| { |
| } |
| void post_init_entity_util_avg(struct task_struct *p) |
| { |
| } |
| static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) |
| { |
| } |
| #endif /* CONFIG_SMP */ |
| |
| /* |
| * Update the current task's runtime statistics. |
| */ |
| static void update_curr(struct cfs_rq *cfs_rq) |
| { |
| struct sched_entity *curr = cfs_rq->curr; |
| u64 now = rq_clock_task(rq_of(cfs_rq)); |
| u64 delta_exec; |
| |
| if (unlikely(!curr)) |
| return; |
| |
| delta_exec = now - curr->exec_start; |
| if (unlikely((s64)delta_exec <= 0)) |
| return; |
| |
| curr->exec_start = now; |
| |
| schedstat_set(curr->statistics.exec_max, |
| max(delta_exec, curr->statistics.exec_max)); |
| |
| curr->sum_exec_runtime += delta_exec; |
| schedstat_add(cfs_rq->exec_clock, delta_exec); |
| |
| curr->vruntime += calc_delta_fair(delta_exec, curr); |
| update_min_vruntime(cfs_rq); |
| |
| if (entity_is_task(curr)) { |
| struct task_struct *curtask = task_of(curr); |
| |
| trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); |
| cgroup_account_cputime(curtask, delta_exec); |
| account_group_exec_runtime(curtask, delta_exec); |
| } |
| |
| account_cfs_rq_runtime(cfs_rq, delta_exec); |
| } |
| |
| static void update_curr_fair(struct rq *rq) |
| { |
| update_curr(cfs_rq_of(&rq->curr->se)); |
| } |
| |
| static inline void |
| update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| u64 wait_start, prev_wait_start; |
| |
| if (!schedstat_enabled()) |
| return; |
| |
| wait_start = rq_clock(rq_of(cfs_rq)); |
| prev_wait_start = schedstat_val(se->statistics.wait_start); |
| |
| if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) && |
| likely(wait_start > prev_wait_start)) |
| wait_start -= prev_wait_start; |
| |
| __schedstat_set(se->statistics.wait_start, wait_start); |
| } |
| |
| static inline void |
| update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| struct task_struct *p; |
| u64 delta; |
| |
| if (!schedstat_enabled()) |
| return; |
| |
| delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start); |
| |
| if (entity_is_task(se)) { |
| p = task_of(se); |
| if (task_on_rq_migrating(p)) { |
| /* |
| * Preserve migrating task's wait time so wait_start |
| * time stamp can be adjusted to accumulate wait time |
| * prior to migration. |
| */ |
| __schedstat_set(se->statistics.wait_start, delta); |
| return; |
| } |
| trace_sched_stat_wait(p, delta); |
| } |
| |
| __schedstat_set(se->statistics.wait_max, |
| max(schedstat_val(se->statistics.wait_max), delta)); |
| __schedstat_inc(se->statistics.wait_count); |
| __schedstat_add(se->statistics.wait_sum, delta); |
| __schedstat_set(se->statistics.wait_start, 0); |
| } |
| |
| static inline void |
| update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| struct task_struct *tsk = NULL; |
| u64 sleep_start, block_start; |
| |
| if (!schedstat_enabled()) |
| return; |
| |
| sleep_start = schedstat_val(se->statistics.sleep_start); |
| block_start = schedstat_val(se->statistics.block_start); |
| |
| if (entity_is_task(se)) |
| tsk = task_of(se); |
| |
| if (sleep_start) { |
| u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start; |
| |
| if ((s64)delta < 0) |
| delta = 0; |
| |
| if (unlikely(delta > schedstat_val(se->statistics.sleep_max))) |
| __schedstat_set(se->statistics.sleep_max, delta); |
| |
| __schedstat_set(se->statistics.sleep_start, 0); |
| __schedstat_add(se->statistics.sum_sleep_runtime, delta); |
| |
| if (tsk) { |
| account_scheduler_latency(tsk, delta >> 10, 1); |
| trace_sched_stat_sleep(tsk, delta); |
| } |
| } |
| if (block_start) { |
| u64 delta = rq_clock(rq_of(cfs_rq)) - block_start; |
| |
| if ((s64)delta < 0) |
| delta = 0; |
| |
| if (unlikely(delta > schedstat_val(se->statistics.block_max))) |
| __schedstat_set(se->statistics.block_max, delta); |
| |
| __schedstat_set(se->statistics.block_start, 0); |
| __schedstat_add(se->statistics.sum_sleep_runtime, delta); |
| |
| if (tsk) { |
| if (tsk->in_iowait) { |
| __schedstat_add(se->statistics.iowait_sum, delta); |
| __schedstat_inc(se->statistics.iowait_count); |
| trace_sched_stat_iowait(tsk, delta); |
| } |
| |
| trace_sched_stat_blocked(tsk, delta); |
| |
| /* |
| * Blocking time is in units of nanosecs, so shift by |
| * 20 to get a milliseconds-range estimation of the |
| * amount of time that the task spent sleeping: |
| */ |
| if (unlikely(prof_on == SLEEP_PROFILING)) { |
| profile_hits(SLEEP_PROFILING, |
| (void *)get_wchan(tsk), |
| delta >> 20); |
| } |
| account_scheduler_latency(tsk, delta >> 10, 0); |
| } |
| } |
| } |
| |
| /* |
| * Task is being enqueued - update stats: |
| */ |
| static inline void |
| update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) |
| { |
| if (!schedstat_enabled()) |
| return; |
| |
| /* |
| * Are we enqueueing a waiting task? (for current tasks |
| * a dequeue/enqueue event is a NOP) |
| */ |
| if (se != cfs_rq->curr) |
| update_stats_wait_start(cfs_rq, se); |
| |
| if (flags & ENQUEUE_WAKEUP) |
| update_stats_enqueue_sleeper(cfs_rq, se); |
| } |
| |
| static inline void |
| update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) |
| { |
| |
| if (!schedstat_enabled()) |
| return; |
| |
| /* |
| * Mark the end of the wait period if dequeueing a |
| * waiting task: |
| */ |
| if (se != cfs_rq->curr) |
| update_stats_wait_end(cfs_rq, se); |
| |
| if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) { |
| struct task_struct *tsk = task_of(se); |
| |
| if (tsk->state & TASK_INTERRUPTIBLE) |
| __schedstat_set(se->statistics.sleep_start, |
| rq_clock(rq_of(cfs_rq))); |
| if (tsk->state & TASK_UNINTERRUPTIBLE) |
| __schedstat_set(se->statistics.block_start, |
| rq_clock(rq_of(cfs_rq))); |
| } |
| } |
| |
| /* |
| * We are picking a new current task - update its stats: |
| */ |
| static inline void |
| update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| /* |
| * We are starting a new run period: |
| */ |
| se->exec_start = rq_clock_task(rq_of(cfs_rq)); |
| } |
| |
| /************************************************** |
| * Scheduling class queueing methods: |
| */ |
| |
| #ifdef CONFIG_NUMA_BALANCING |
| /* |
| * Approximate time to scan a full NUMA task in ms. The task scan period is |
| * calculated based on the tasks virtual memory size and |
| * numa_balancing_scan_size. |
| */ |
| unsigned int sysctl_numa_balancing_scan_period_min = 1000; |
| unsigned int sysctl_numa_balancing_scan_period_max = 60000; |
| |
| /* Portion of address space to scan in MB */ |
| unsigned int sysctl_numa_balancing_scan_size = 256; |
| |
| /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ |
| unsigned int sysctl_numa_balancing_scan_delay = 1000; |
| |
| struct numa_group { |
| refcount_t refcount; |
| |
| spinlock_t lock; /* nr_tasks, tasks */ |
| int nr_tasks; |
| pid_t gid; |
| int active_nodes; |
| |
| struct rcu_head rcu; |
| unsigned long total_faults; |
| unsigned long max_faults_cpu; |
| /* |
| * Faults_cpu is used to decide whether memory should move |
| * towards the CPU. As a consequence, these stats are weighted |
| * more by CPU use than by memory faults. |
| */ |
| unsigned long *faults_cpu; |
| unsigned long faults[0]; |
| }; |
| |
| /* |
| * For functions that can be called in multiple contexts that permit reading |
| * ->numa_group (see struct task_struct for locking rules). |
| */ |
| static struct numa_group *deref_task_numa_group(struct task_struct *p) |
| { |
| return rcu_dereference_check(p->numa_group, p == current || |
| (lockdep_is_held(&task_rq(p)->lock) && !READ_ONCE(p->on_cpu))); |
| } |
| |
| static struct numa_group *deref_curr_numa_group(struct task_struct *p) |
| { |
| return rcu_dereference_protected(p->numa_group, p == current); |
| } |
| |
| static inline unsigned long group_faults_priv(struct numa_group *ng); |
| static inline unsigned long group_faults_shared(struct numa_group *ng); |
| |
| static unsigned int task_nr_scan_windows(struct task_struct *p) |
| { |
| unsigned long rss = 0; |
| unsigned long nr_scan_pages; |
| |
| /* |
| * Calculations based on RSS as non-present and empty pages are skipped |
| * by the PTE scanner and NUMA hinting faults should be trapped based |
| * on resident pages |
| */ |
| nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT); |
| rss = get_mm_rss(p->mm); |
| if (!rss) |
| rss = nr_scan_pages; |
| |
| rss = round_up(rss, nr_scan_pages); |
| return rss / nr_scan_pages; |
| } |
| |
| /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */ |
| #define MAX_SCAN_WINDOW 2560 |
| |
| static unsigned int task_scan_min(struct task_struct *p) |
| { |
| unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size); |
| unsigned int scan, floor; |
| unsigned int windows = 1; |
| |
| if (scan_size < MAX_SCAN_WINDOW) |
| windows = MAX_SCAN_WINDOW / scan_size; |
| floor = 1000 / windows; |
| |
| scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p); |
| return max_t(unsigned int, floor, scan); |
| } |
| |
| static unsigned int task_scan_start(struct task_struct *p) |
| { |
| unsigned long smin = task_scan_min(p); |
| unsigned long period = smin; |
| struct numa_group *ng; |
| |
| /* Scale the maximum scan period with the amount of shared memory. */ |
| rcu_read_lock(); |
| ng = rcu_dereference(p->numa_group); |
| if (ng) { |
| unsigned long shared = group_faults_shared(ng); |
| unsigned long private = group_faults_priv(ng); |
| |
| period *= refcount_read(&ng->refcount); |
| period *= shared + 1; |
| period /= private + shared + 1; |
| } |
| rcu_read_unlock(); |
| |
| return max(smin, period); |
| } |
| |
| static unsigned int task_scan_max(struct task_struct *p) |
| { |
| unsigned long smin = task_scan_min(p); |
| unsigned long smax; |
| struct numa_group *ng; |
| |
| /* Watch for min being lower than max due to floor calculations */ |
| smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p); |
| |
| /* Scale the maximum scan period with the amount of shared memory. */ |
| ng = deref_curr_numa_group(p); |
| if (ng) { |
| unsigned long shared = group_faults_shared(ng); |
| unsigned long private = group_faults_priv(ng); |
| unsigned long period = smax; |
| |
| period *= refcount_read(&ng->refcount); |
| period *= shared + 1; |
| period /= private + shared + 1; |
| |
| smax = max(smax, period); |
| } |
| |
| return max(smin, smax); |
| } |
| |
| static void account_numa_enqueue(struct rq *rq, struct task_struct *p) |
| { |
| rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE); |
| rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p)); |
| } |
| |
| static void account_numa_dequeue(struct rq *rq, struct task_struct *p) |
| { |
| rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE); |
| rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p)); |
| } |
| |
| /* Shared or private faults. */ |
| #define NR_NUMA_HINT_FAULT_TYPES 2 |
| |
| /* Memory and CPU locality */ |
| #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2) |
| |
| /* Averaged statistics, and temporary buffers. */ |
| #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2) |
| |
| pid_t task_numa_group_id(struct task_struct *p) |
| { |
| struct numa_group *ng; |
| pid_t gid = 0; |
| |
| rcu_read_lock(); |
| ng = rcu_dereference(p->numa_group); |
| if (ng) |
| gid = ng->gid; |
| rcu_read_unlock(); |
| |
| return gid; |
| } |
| |
| /* |
| * The averaged statistics, shared & private, memory & CPU, |
| * occupy the first half of the array. The second half of the |
| * array is for current counters, which are averaged into the |
| * first set by task_numa_placement. |
| */ |
| static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv) |
| { |
| return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv; |
| } |
| |
| static inline unsigned long task_faults(struct task_struct *p, int nid) |
| { |
| if (!p->numa_faults) |
| return 0; |
| |
| return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] + |
| p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)]; |
| } |
| |
| static inline unsigned long group_faults(struct task_struct *p, int nid) |
| { |
| struct numa_group *ng = deref_task_numa_group(p); |
| |
| if (!ng) |
| return 0; |
| |
| return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] + |
| ng->faults[task_faults_idx(NUMA_MEM, nid, 1)]; |
| } |
| |
| static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) |
| { |
| return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] + |
| group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)]; |
| } |
| |
| static inline unsigned long group_faults_priv(struct numa_group *ng) |
| { |
| unsigned long faults = 0; |
| int node; |
| |
| for_each_online_node(node) { |
| faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)]; |
| } |
| |
| return faults; |
| } |
| |
| static inline unsigned long group_faults_shared(struct numa_group *ng) |
| { |
| unsigned long faults = 0; |
| int node; |
| |
| for_each_online_node(node) { |
| faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)]; |
| } |
| |
| return faults; |
| } |
| |
| /* |
| * A node triggering more than 1/3 as many NUMA faults as the maximum is |
| * considered part of a numa group's pseudo-interleaving set. Migrations |
| * between these nodes are slowed down, to allow things to settle down. |
| */ |
| #define ACTIVE_NODE_FRACTION 3 |
| |
| static bool numa_is_active_node(int nid, struct numa_group *ng) |
| { |
| return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu; |
| } |
| |
| /* Handle placement on systems where not all nodes are directly connected. */ |
| static unsigned long score_nearby_nodes(struct task_struct *p, int nid, |
| int maxdist, bool task) |
| { |
| unsigned long score = 0; |
| int node; |
| |
| /* |
| * All nodes are directly connected, and the same distance |
| * from each other. No need for fancy placement algorithms. |
| */ |
| if (sched_numa_topology_type == NUMA_DIRECT) |
| return 0; |
| |
| /* |
| * This code is called for each node, introducing N^2 complexity, |
| * which should be ok given the number of nodes rarely exceeds 8. |
| */ |
| for_each_online_node(node) { |
| unsigned long faults; |
| int dist = node_distance(nid, node); |
| |
| /* |
| * The furthest away nodes in the system are not interesting |
| * for placement; nid was already counted. |
| */ |
| if (dist == sched_max_numa_distance || node == nid) |
| continue; |
| |
| /* |
| * On systems with a backplane NUMA topology, compare groups |
| * of nodes, and move tasks towards the group with the most |
| * memory accesses. When comparing two nodes at distance |
| * "hoplimit", only nodes closer by than "hoplimit" are part |
| * of each group. Skip other nodes. |
| */ |
| if (sched_numa_topology_type == NUMA_BACKPLANE && |
| dist >= maxdist) |
| continue; |
| |
| /* Add up the faults from nearby nodes. */ |
| if (task) |
| faults = task_faults(p, node); |
| else |
| faults = group_faults(p, node); |
| |
| /* |
| * On systems with a glueless mesh NUMA topology, there are |
| * no fixed "groups of nodes". Instead, nodes that are not |
| * directly connected bounce traffic through intermediate |
| * nodes; a numa_group can occupy any set of nodes. |
| * The further away a node is, the less the faults count. |
| * This seems to result in good task placement. |
| */ |
| if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { |
| faults *= (sched_max_numa_distance - dist); |
| faults /= (sched_max_numa_distance - LOCAL_DISTANCE); |
| } |
| |
| score += faults; |
| } |
| |
| return score; |
| } |
| |
| /* |
| * These return the fraction of accesses done by a particular task, or |
| * task group, on a particular numa node. The group weight is given a |
| * larger multiplier, in order to group tasks together that are almost |
| * evenly spread out between numa nodes. |
| */ |
| static inline unsigned long task_weight(struct task_struct *p, int nid, |
| int dist) |
| { |
| unsigned long faults, total_faults; |
| |
| if (!p->numa_faults) |
| return 0; |
| |
| total_faults = p->total_numa_faults; |
| |
| if (!total_faults) |
| return 0; |
| |
| faults = task_faults(p, nid); |
| faults += score_nearby_nodes(p, nid, dist, true); |
| |
| return 1000 * faults / total_faults; |
| } |
| |
| static inline unsigned long group_weight(struct task_struct *p, int nid, |
| int dist) |
| { |
| struct numa_group *ng = deref_task_numa_group(p); |
| unsigned long faults, total_faults; |
| |
| if (!ng) |
| return 0; |
| |
| total_faults = ng->total_faults; |
| |
| if (!total_faults) |
| return 0; |
| |
| faults = group_faults(p, nid); |
| faults += score_nearby_nodes(p, nid, dist, false); |
| |
| return 1000 * faults / total_faults; |
| } |
| |
| bool should_numa_migrate_memory(struct task_struct *p, struct page * page, |
| int src_nid, int dst_cpu) |
| { |
| struct numa_group *ng = deref_curr_numa_group(p); |
| int dst_nid = cpu_to_node(dst_cpu); |
| int last_cpupid, this_cpupid; |
| |
| this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); |
| last_cpupid = page_cpupid_xchg_last(page, this_cpupid); |
| |
| /* |
| * Allow first faults or private faults to migrate immediately early in |
| * the lifetime of a task. The magic number 4 is based on waiting for |
| * two full passes of the "multi-stage node selection" test that is |
| * executed below. |
| */ |
| if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) && |
| (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid))) |
| return true; |
| |
| /* |
| * Multi-stage node selection is used in conjunction with a periodic |
| * migration fault to build a temporal task<->page relation. By using |
| * a two-stage filter we remove short/unlikely relations. |
| * |
| * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate |
| * a task's usage of a particular page (n_p) per total usage of this |
| * page (n_t) (in a given time-span) to a probability. |
| * |
| * Our periodic faults will sample this probability and getting the |
| * same result twice in a row, given these samples are fully |
| * independent, is then given by P(n)^2, provided our sample period |
| * is sufficiently short compared to the usage pattern. |
| * |
| * This quadric squishes small probabilities, making it less likely we |
| * act on an unlikely task<->page relation. |
| */ |
| if (!cpupid_pid_unset(last_cpupid) && |
| cpupid_to_nid(last_cpupid) != dst_nid) |
| return false; |
| |
| /* Always allow migrate on private faults */ |
| if (cpupid_match_pid(p, last_cpupid)) |
| return true; |
| |
| /* A shared fault, but p->numa_group has not been set up yet. */ |
| if (!ng) |
| return true; |
| |
| /* |
| * Destination node is much more heavily used than the source |
| * node? Allow migration. |
| */ |
| if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) * |
| ACTIVE_NODE_FRACTION) |
| return true; |
| |
| /* |
| * Distribute memory according to CPU & memory use on each node, |
| * with 3/4 hysteresis to avoid unnecessary memory migrations: |
| * |
| * faults_cpu(dst) 3 faults_cpu(src) |
| * --------------- * - > --------------- |
| * faults_mem(dst) 4 faults_mem(src) |
| */ |
| return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 > |
| group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4; |
| } |
| |
| static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq); |
| |
| static unsigned long cpu_runnable_load(struct rq *rq) |
| { |
| return cfs_rq_runnable_load_avg(&rq->cfs); |
| } |
| |
| /* Cached statistics for all CPUs within a node */ |
| struct numa_stats { |
| unsigned long load; |
| |
| /* Total compute capacity of CPUs on a node */ |
| unsigned long compute_capacity; |
| }; |
| |
| /* |
| * XXX borrowed from update_sg_lb_stats |
| */ |
| static void update_numa_stats(struct numa_stats *ns, int nid) |
| { |
| int cpu; |
| |
| memset(ns, 0, sizeof(*ns)); |
| for_each_cpu(cpu, cpumask_of_node(nid)) { |
| struct rq *rq = cpu_rq(cpu); |
| |
| ns->load += cpu_runnable_load(rq); |
| ns->compute_capacity += capacity_of(cpu); |
| } |
| |
| } |
| |
| struct task_numa_env { |
| struct task_struct *p; |
| |
| int src_cpu, src_nid; |
| int dst_cpu, dst_nid; |
| |
| struct numa_stats src_stats, dst_stats; |
| |
| int imbalance_pct; |
| int dist; |
| |
| struct task_struct *best_task; |
| long best_imp; |
| int best_cpu; |
| }; |
| |
| static void task_numa_assign(struct task_numa_env *env, |
| struct task_struct *p, long imp) |
| { |
| struct rq *rq = cpu_rq(env->dst_cpu); |
| |
| /* Bail out if run-queue part of active NUMA balance. */ |
| if (xchg(&rq->numa_migrate_on, 1)) |
| return; |
| |
| /* |
| * Clear previous best_cpu/rq numa-migrate flag, since task now |
| * found a better CPU to move/swap. |
| */ |
| if (env->best_cpu != -1) { |
| rq = cpu_rq(env->best_cpu); |
| WRITE_ONCE(rq->numa_migrate_on, 0); |
| } |
| |
| if (env->best_task) |
| put_task_struct(env->best_task); |
| if (p) |
| get_task_struct(p); |
| |
| env->best_task = p; |
| env->best_imp = imp; |
| env->best_cpu = env->dst_cpu; |
| } |
| |
| static bool load_too_imbalanced(long src_load, long dst_load, |
| struct task_numa_env *env) |
| { |
| long imb, old_imb; |
| long orig_src_load, orig_dst_load; |
| long src_capacity, dst_capacity; |
| |
| /* |
| * The load is corrected for the CPU capacity available on each node. |
| * |
| * src_load dst_load |
| * ------------ vs --------- |
| * src_capacity dst_capacity |
| */ |
| src_capacity = env->src_stats.compute_capacity; |
| dst_capacity = env->dst_stats.compute_capacity; |
| |
| imb = abs(dst_load * src_capacity - src_load * dst_capacity); |
| |
| orig_src_load = env->src_stats.load; |
| orig_dst_load = env->dst_stats.load; |
| |
| old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity); |
| |
| /* Would this change make things worse? */ |
| return (imb > old_imb); |
| } |
| |
| /* |
| * Maximum NUMA importance can be 1998 (2*999); |
| * SMALLIMP @ 30 would be close to 1998/64. |
| * Used to deter task migration. |
| */ |
| #define SMALLIMP 30 |
| |
| /* |
| * This checks if the overall compute and NUMA accesses of the system would |
| * be improved if the source tasks was migrated to the target dst_cpu taking |
| * into account that it might be best if task running on the dst_cpu should |
| * be exchanged with the source task |
| */ |
| static void task_numa_compare(struct task_numa_env *env, |
| long taskimp, long groupimp, bool maymove) |
| { |
| struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p); |
| struct rq *dst_rq = cpu_rq(env->dst_cpu); |
| long imp = p_ng ? groupimp : taskimp; |
| struct task_struct *cur; |
| long src_load, dst_load; |
| int dist = env->dist; |
| long moveimp = imp; |
| long load; |
| |
| if (READ_ONCE(dst_rq->numa_migrate_on)) |
| return; |
| |
| rcu_read_lock(); |
| cur = rcu_dereference(dst_rq->curr); |
| if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) |
| cur = NULL; |
| |
| /* |
| * Because we have preemption enabled we can get migrated around and |
| * end try selecting ourselves (current == env->p) as a swap candidate. |
| */ |
| if (cur == env->p) |
| goto unlock; |
| |
| if (!cur) { |
| if (maymove && moveimp >= env->best_imp) |
| goto assign; |
| else |
| goto unlock; |
| } |
| |
| /* |
| * "imp" is the fault differential for the source task between the |
| * source and destination node. Calculate the total differential for |
| * the source task and potential destination task. The more negative |
| * the value is, the more remote accesses that would be expected to |
| * be incurred if the tasks were swapped. |
| */ |
| /* Skip this swap candidate if cannot move to the source cpu */ |
| if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr)) |
| goto unlock; |
| |
| /* |
| * If dst and source tasks are in the same NUMA group, or not |
| * in any group then look only at task weights. |
| */ |
| cur_ng = rcu_dereference(cur->numa_group); |
| if (cur_ng == p_ng) { |
| imp = taskimp + task_weight(cur, env->src_nid, dist) - |
| task_weight(cur, env->dst_nid, dist); |
| /* |
| * Add some hysteresis to prevent swapping the |
| * tasks within a group over tiny differences. |
| */ |
| if (cur_ng) |
| imp -= imp / 16; |
| } else { |
| /* |
| * Compare the group weights. If a task is all by itself |
| * (not part of a group), use the task weight instead. |
| */ |
| if (cur_ng && p_ng) |
| imp += group_weight(cur, env->src_nid, dist) - |
| group_weight(cur, env->dst_nid, dist); |
| else |
| imp += task_weight(cur, env->src_nid, dist) - |
| task_weight(cur, env->dst_nid, dist); |
| } |
| |
| if (maymove && moveimp > imp && moveimp > env->best_imp) { |
| imp = moveimp; |
| cur = NULL; |
| goto assign; |
| } |
| |
| /* |
| * If the NUMA importance is less than SMALLIMP, |
| * task migration might only result in ping pong |
| * of tasks and also hurt performance due to cache |
| * misses. |
| */ |
| if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2) |
| goto unlock; |
| |
| /* |
| * In the overloaded case, try and keep the load balanced. |
| */ |
| load = task_h_load(env->p) - task_h_load(cur); |
| if (!load) |
| goto assign; |
| |
| dst_load = env->dst_stats.load + load; |
| src_load = env->src_stats.load - load; |
| |
| if (load_too_imbalanced(src_load, dst_load, env)) |
| goto unlock; |
| |
| assign: |
| /* |
| * One idle CPU per node is evaluated for a task numa move. |
| * Call select_idle_sibling to maybe find a better one. |
| */ |
| if (!cur) { |
| /* |
| * select_idle_siblings() uses an per-CPU cpumask that |
| * can be used from IRQ context. |
| */ |
| local_irq_disable(); |
| env->dst_cpu = select_idle_sibling(env->p, env->src_cpu, |
| env->dst_cpu); |
| local_irq_enable(); |
| } |
| |
| task_numa_assign(env, cur, imp); |
| unlock: |
| rcu_read_unlock(); |
| } |
| |
| static void task_numa_find_cpu(struct task_numa_env *env, |
| long taskimp, long groupimp) |
| { |
| long src_load, dst_load, load; |
| bool maymove = false; |
| int cpu; |
| |
| load = task_h_load(env->p); |
| dst_load = env->dst_stats.load + load; |
| src_load = env->src_stats.load - load; |
| |
| /* |
| * If the improvement from just moving env->p direction is better |
| * than swapping tasks around, check if a move is possible. |
| */ |
| maymove = !load_too_imbalanced(src_load, dst_load, env); |
| |
| for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { |
| /* Skip this CPU if the source task cannot migrate */ |
| if (!cpumask_test_cpu(cpu, env->p->cpus_ptr)) |
| continue; |
| |
| env->dst_cpu = cpu; |
| task_numa_compare(env, taskimp, groupimp, maymove); |
| } |
| } |
| |
| static int task_numa_migrate(struct task_struct *p) |
| { |
| struct task_numa_env env = { |
| .p = p, |
| |
| .src_cpu = task_cpu(p), |
| .src_nid = task_node(p), |
| |
| .imbalance_pct = 112, |
| |
| .best_task = NULL, |
| .best_imp = 0, |
| .best_cpu = -1, |
| }; |
| unsigned long taskweight, groupweight; |
| struct sched_domain *sd; |
| long taskimp, groupimp; |
| struct numa_group *ng; |
| struct rq *best_rq; |
| int nid, ret, dist; |
| |
| /* |
| * Pick the lowest SD_NUMA domain, as that would have the smallest |
| * imbalance and would be the first to start moving tasks about. |
| * |
| * And we want to avoid any moving of tasks about, as that would create |
| * random movement of tasks -- counter the numa conditions we're trying |
| * to satisfy here. |
| */ |
| rcu_read_lock(); |
| sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); |
| if (sd) |
| env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; |
| rcu_read_unlock(); |
| |
| /* |
| * Cpusets can break the scheduler domain tree into smaller |
| * balance domains, some of which do not cross NUMA boundaries. |
| * Tasks that are "trapped" in such domains cannot be migrated |
| * elsewhere, so there is no point in (re)trying. |
| */ |
| if (unlikely(!sd)) { |
| sched_setnuma(p, task_node(p)); |
| return -EINVAL; |
| } |
| |
| env.dst_nid = p->numa_preferred_nid; |
| dist = env.dist = node_distance(env.src_nid, env.dst_nid); |
| taskweight = task_weight(p, env.src_nid, dist); |
| groupweight = group_weight(p, env.src_nid, dist); |
| update_numa_stats(&env.src_stats, env.src_nid); |
| taskimp = task_weight(p, env.dst_nid, dist) - taskweight; |
| groupimp = group_weight(p, env.dst_nid, dist) - groupweight; |
| update_numa_stats(&env.dst_stats, env.dst_nid); |
| |
| /* Try to find a spot on the preferred nid. */ |
| task_numa_find_cpu(&env, taskimp, groupimp); |
| |
| /* |
| * Look at other nodes in these cases: |
| * - there is no space available on the preferred_nid |
| * - the task is part of a numa_group that is interleaved across |
| * multiple NUMA nodes; in order to better consolidate the group, |
| * we need to check other locations. |
| */ |
| ng = deref_curr_numa_group(p); |
| if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) { |
| for_each_online_node(nid) { |
| if (nid == env.src_nid || nid == p->numa_preferred_nid) |
| continue; |
| |
| dist = node_distance(env.src_nid, env.dst_nid); |
| if (sched_numa_topology_type == NUMA_BACKPLANE && |
| dist != env.dist) { |
| taskweight = task_weight(p, env.src_nid, dist); |
| groupweight = group_weight(p, env.src_nid, dist); |
| } |
| |
| /* Only consider nodes where both task and groups benefit */ |
| taskimp = task_weight(p, nid, dist) - taskweight; |
| groupimp = group_weight(p, nid, dist) - groupweight; |
| if (taskimp < 0 && groupimp < 0) |
| continue; |
| |
| env.dist = dist; |
| env.dst_nid = nid; |
| update_numa_stats(&env.dst_stats, env.dst_nid); |
| task_numa_find_cpu(&env, taskimp, groupimp); |
| } |
| } |
| |
| /* |
| * If the task is part of a workload that spans multiple NUMA nodes, |
| * and is migrating into one of the workload's active nodes, remember |
| * this node as the task's preferred numa node, so the workload can |
| * settle down. |
| * A task that migrated to a second choice node will be better off |
| * trying for a better one later. Do not set the preferred node here. |
| */ |
| if (ng) { |
| if (env.best_cpu == -1) |
| nid = env.src_nid; |
| else |
| nid = cpu_to_node(env.best_cpu); |
| |
| if (nid != p->numa_preferred_nid) |
| sched_setnuma(p, nid); |
| } |
| |
| /* No better CPU than the current one was found. */ |
| if (env.best_cpu == -1) |
| return -EAGAIN; |
| |
| best_rq = cpu_rq(env.best_cpu); |
| if (env.best_task == NULL) { |
| ret = migrate_task_to(p, env.best_cpu); |
| WRITE_ONCE(best_rq->numa_migrate_on, 0); |
| if (ret != 0) |
| trace_sched_stick_numa(p, env.src_cpu, env.best_cpu); |
| return ret; |
| } |
| |
| ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu); |
| WRITE_ONCE(best_rq->numa_migrate_on, 0); |
| |
| if (ret != 0) |
| trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task)); |
| put_task_struct(env.best_task); |
| return ret; |
| } |
| |
| /* Attempt to migrate a task to a CPU on the preferred node. */ |
| static void numa_migrate_preferred(struct task_struct *p) |
| { |
| unsigned long interval = HZ; |
| |
| /* This task has no NUMA fault statistics yet */ |
| if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults)) |
| return; |
| |
| /* Periodically retry migrating the task to the preferred node */ |
| interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16); |
| p->numa_migrate_retry = jiffies + interval; |
| |
| /* Success if task is already running on preferred CPU */ |
| if (task_node(p) == p->numa_preferred_nid) |
| return; |
| |
| /* Otherwise, try migrate to a CPU on the preferred node */ |
| task_numa_migrate(p); |
| } |
| |
| /* |
| * Find out how many nodes on the workload is actively running on. Do this by |
| * tracking the nodes from which NUMA hinting faults are triggered. This can |
| * be different from the set of nodes where the workload's memory is currently |
| * located. |
| */ |
| static void numa_group_count_active_nodes(struct numa_group *numa_group) |
| { |
| unsigned long faults, max_faults = 0; |
| int nid, active_nodes = 0; |
| |
| for_each_online_node(nid) { |
| faults = group_faults_cpu(numa_group, nid); |
| if (faults > max_faults) |
| max_faults = faults; |
| } |
| |
| for_each_online_node(nid) { |
| faults = group_faults_cpu(numa_group, nid); |
| if (faults * ACTIVE_NODE_FRACTION > max_faults) |
| active_nodes++; |
| } |
| |
| numa_group->max_faults_cpu = max_faults; |
| numa_group->active_nodes = active_nodes; |
| } |
| |
| /* |
| * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS |
| * increments. The more local the fault statistics are, the higher the scan |
| * period will be for the next scan window. If local/(local+remote) ratio is |
| * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) |
| * the scan period will decrease. Aim for 70% local accesses. |
| */ |
| #define NUMA_PERIOD_SLOTS 10 |
| #define NUMA_PERIOD_THRESHOLD 7 |
| |
| /* |
| * Increase the scan period (slow down scanning) if the majority of |
| * our memory is already on our local node, or if the majority of |
| * the page accesses are shared with other processes. |
| * Otherwise, decrease the scan period. |
| */ |
| static void update_task_scan_period(struct task_struct *p, |
| unsigned long shared, unsigned long private) |
| { |
| unsigned int period_slot; |
| int lr_ratio, ps_ratio; |
| int diff; |
| |
| unsigned long remote = p->numa_faults_locality[0]; |
| unsigned long local = p->numa_faults_locality[1]; |
| |
| /* |
| * If there were no record hinting faults then either the task is |
| * completely idle or all activity is areas that are not of interest |
| * to automatic numa balancing. Related to that, if there were failed |
| * migration then it implies we are migrating too quickly or the local |
| * node is overloaded. In either case, scan slower |
| */ |
| if (local + shared == 0 || p->numa_faults_locality[2]) { |
| p->numa_scan_period = min(p->numa_scan_period_max, |
| p->numa_scan_period << 1); |
| |
| p->mm->numa_next_scan = jiffies + |
| msecs_to_jiffies(p->numa_scan_period); |
| |
| return; |
| } |
| |
| /* |
| * Prepare to scale scan period relative to the current period. |
| * == NUMA_PERIOD_THRESHOLD scan period stays the same |
| * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster) |
| * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower) |
| */ |
| period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS); |
| lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote); |
| ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared); |
| |
| if (ps_ratio >= NUMA_PERIOD_THRESHOLD) { |
| /* |
| * Most memory accesses are local. There is no need to |
| * do fast NUMA scanning, since memory is already local. |
| */ |
| int slot = ps_ratio - NUMA_PERIOD_THRESHOLD; |
| if (!slot) |
| slot = 1; |
| diff = slot * period_slot; |
| } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) { |
| /* |
| * Most memory accesses are shared with other tasks. |
| * There is no point in continuing fast NUMA scanning, |
| * since other tasks may just move the memory elsewhere. |
| */ |
| int slot = lr_ratio - NUMA_PERIOD_THRESHOLD; |
| if (!slot) |
| slot = 1; |
| diff = slot * period_slot; |
| } else { |
| /* |
| * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS, |
| * yet they are not on the local NUMA node. Speed up |
| * NUMA scanning to get the memory moved over. |
| */ |
| int ratio = max(lr_ratio, ps_ratio); |
| diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot; |
| } |
| |
| p->numa_scan_period = clamp(p->numa_scan_period + diff, |
| task_scan_min(p), task_scan_max(p)); |
| memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); |
| } |
| |
| /* |
| * Get the fraction of time the task has been running since the last |
| * NUMA placement cycle. The scheduler keeps similar statistics, but |
| * decays those on a 32ms period, which is orders of magnitude off |
| * from the dozens-of-seconds NUMA balancing period. Use the scheduler |
| * stats only if the task is so new there are no NUMA statistics yet. |
| */ |
| static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) |
| { |
| u64 runtime, delta, now; |
| /* Use the start of this time slice to avoid calculations. */ |
| now = p->se.exec_start; |
| runtime = p->se.sum_exec_runtime; |
| |
| if (p->last_task_numa_placement) { |
| delta = runtime - p->last_sum_exec_runtime; |
| *period = now - p->last_task_numa_placement; |
| |
| /* Avoid time going backwards, prevent potential divide error: */ |
| if (unlikely((s64)*period < 0)) |
| *period = 0; |
| } else { |
| delta = p->se.avg.load_sum; |
| *period = LOAD_AVG_MAX; |
| } |
| |
| p->last_sum_exec_runtime = runtime; |
| p->last_task_numa_placement = now; |
| |
| return delta; |
| } |
| |
| /* |
| * Determine the preferred nid for a task in a numa_group. This needs to |
| * be done in a way that produces consistent results with group_weight, |
| * otherwise workloads might not converge. |
| */ |
| static int preferred_group_nid(struct task_struct *p, int nid) |
| { |
| nodemask_t nodes; |
| int dist; |
| |
| /* Direct connections between all NUMA nodes. */ |
| if (sched_numa_topology_type == NUMA_DIRECT) |
| return nid; |
| |
| /* |
| * On a system with glueless mesh NUMA topology, group_weight |
| * scores nodes according to the number of NUMA hinting faults on |
| * both the node itself, and on nearby nodes. |
| */ |
| if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { |
| unsigned long score, max_score = 0; |
| int node, max_node = nid; |
| |
| dist = sched_max_numa_distance; |
| |
| for_each_online_node(node) { |
| score = group_weight(p, node, dist); |
| if (score > max_score) { |
| max_score = score; |
| max_node = node; |
| } |
| } |
| return max_node; |
| } |
| |
| /* |
| * Finding the preferred nid in a system with NUMA backplane |
| * interconnect topology is more involved. The goal is to locate |
| * tasks from numa_groups near each other in the system, and |
| * untangle workloads from different sides of the system. This requires |
| * searching down the hierarchy of node groups, recursively searching |
| * inside the highest scoring group of nodes. The nodemask tricks |
| * keep the complexity of the search down. |
| */ |
| nodes = node_online_map; |
| for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) { |
| unsigned long max_faults = 0; |
| nodemask_t max_group = NODE_MASK_NONE; |
| int a, b; |
| |
| /* Are there nodes at this distance from each other? */ |
| if (!find_numa_distance(dist)) |
| continue; |
| |
| for_each_node_mask(a, nodes) { |
| unsigned long faults = 0; |
| nodemask_t this_group; |
| nodes_clear(this_group); |
| |
| /* Sum group's NUMA faults; includes a==b case. */ |
| for_each_node_mask(b, nodes) { |
| if (node_distance(a, b) < dist) { |
| faults += group_faults(p, b); |
| node_set(b, this_group); |
| node_clear(b, nodes); |
| } |
| } |
| |
| /* Remember the top group. */ |
| if (faults > max_faults) { |
| max_faults = faults; |
| max_group = this_group; |
| /* |
| * subtle: at the smallest distance there is |
| * just one node left in each "group", the |
| * winner is the preferred nid. |
| */ |
| nid = a; |
| } |
| } |
| /* Next round, evaluate the nodes within max_group. */ |
| if (!max_faults) |
| break; |
| nodes = max_group; |
| } |
| return nid; |
| } |
| |
| static void task_numa_placement(struct task_struct *p) |
| { |
| int seq, nid, max_nid = NUMA_NO_NODE; |
| unsigned long max_faults = 0; |
| unsigned long fault_types[2] = { 0, 0 }; |
| unsigned long total_faults; |
| u64 runtime, period; |
| spinlock_t *group_lock = NULL; |
| struct numa_group *ng; |
| |
| /* |
| * The p->mm->numa_scan_seq field gets updated without |
| * exclusive access. Use READ_ONCE() here to ensure |
| * that the field is read in a single access: |
| */ |
| seq = READ_ONCE(p->mm->numa_scan_seq); |
| if (p->numa_scan_seq == seq) |
| return; |
| p->numa_scan_seq = seq; |
| p->numa_scan_period_max = task_scan_max(p); |
| |
| total_faults = p->numa_faults_locality[0] + |
| p->numa_faults_locality[1]; |
| runtime = numa_get_avg_runtime(p, &period); |
| |
| /* If the task is part of a group prevent parallel updates to group stats */ |
| ng = deref_curr_numa_group(p); |
| if (ng) { |
| group_lock = &ng->lock; |
| spin_lock_irq(group_lock); |
| } |
| |
| /* Find the node with the highest number of faults */ |
| for_each_online_node(nid) { |
| /* Keep track of the offsets in numa_faults array */ |
| int mem_idx, membuf_idx, cpu_idx, cpubuf_idx; |
| unsigned long faults = 0, group_faults = 0; |
| int priv; |
| |
| for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) { |
| long diff, f_diff, f_weight; |
| |
| mem_idx = task_faults_idx(NUMA_MEM, nid, priv); |
| membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv); |
| cpu_idx = task_faults_idx(NUMA_CPU, nid, priv); |
| cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv); |
| |
| /* Decay existing window, copy faults since last scan */ |
| diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2; |
| fault_types[priv] += p->numa_faults[membuf_idx]; |
| p->numa_faults[membuf_idx] = 0; |
| |
| /* |
| * Normalize the faults_from, so all tasks in a group |
| * count according to CPU use, instead of by the raw |
| * number of faults. Tasks with little runtime have |
| * little over-all impact on throughput, and thus their |
| * faults are less important. |
| */ |
| f_weight = div64_u64(runtime << 16, period + 1); |
| f_weight = (f_weight * p->numa_faults[cpubuf_idx]) / |
| (total_faults + 1); |
| f_diff = f_weight - p->numa_faults[cpu_idx] / 2; |
| p->numa_faults[cpubuf_idx] = 0; |
| |
| p->numa_faults[mem_idx] += diff; |
| p->numa_faults[cpu_idx] += f_diff; |
| faults += p->numa_faults[mem_idx]; |
| p->total_numa_faults += diff; |
| if (ng) { |
| /* |
| * safe because we can only change our own group |
| * |
| * mem_idx represents the offset for a given |
| * nid and priv in a specific region because it |
| * is at the beginning of the numa_faults array. |
| */ |
| ng->faults[mem_idx] += diff; |
| ng->faults_cpu[mem_idx] += f_diff; |
| ng->total_faults += diff; |
| group_faults += ng->faults[mem_idx]; |
| } |
| } |
| |
| if (!ng) { |
| if (faults > max_faults) { |
| max_faults = faults; |
| max_nid = nid; |
| } |
| } else if (group_faults > max_faults) { |
| max_faults = group_faults; |
| max_nid = nid; |
| } |
| } |
| |
| if (ng) { |
| numa_group_count_active_nodes(ng); |
| spin_unlock_irq(group_lock); |
| max_nid = preferred_group_nid(p, max_nid); |
| } |
| |
| if (max_faults) { |
| /* Set the new preferred node */ |
| if (max_nid != p->numa_preferred_nid) |
| sched_setnuma(p, max_nid); |
| } |
| |
| update_task_scan_period(p, fault_types[0], fault_types[1]); |
| } |
| |
| static inline int get_numa_group(struct numa_group *grp) |
| { |
| return refcount_inc_not_zero(&grp->refcount); |
| } |
| |
| static inline void put_numa_group(struct numa_group *grp) |
| { |
| if (refcount_dec_and_test(&grp->refcount)) |
| kfree_rcu(grp, rcu); |
| } |
| |
| static void task_numa_group(struct task_struct *p, int cpupid, int flags, |
| int *priv) |
| { |
| struct numa_group *grp, *my_grp; |
| struct task_struct *tsk; |
| bool join = false; |
| int cpu = cpupid_to_cpu(cpupid); |
| int i; |
| |
| if (unlikely(!deref_curr_numa_group(p))) { |
| unsigned int size = sizeof(struct numa_group) + |
| 4*nr_node_ids*sizeof(unsigned long); |
| |
| grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); |
| if (!grp) |
| return; |
| |
| refcount_set(&grp->refcount, 1); |
| grp->active_nodes = 1; |
| grp->max_faults_cpu = 0; |
| spin_lock_init(&grp->lock); |
| grp->gid = p->pid; |
| /* Second half of the array tracks nids where faults happen */ |
| grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * |
| nr_node_ids; |
| |
| for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) |
| grp->faults[i] = p->numa_faults[i]; |
| |
| grp->total_faults = p->total_numa_faults; |
| |
| grp->nr_tasks++; |
| rcu_assign_pointer(p->numa_group, grp); |
| } |
| |
| rcu_read_lock(); |
| tsk = READ_ONCE(cpu_rq(cpu)->curr); |
| |
| if (!cpupid_match_pid(tsk, cpupid)) |
| goto no_join; |
| |
| grp = rcu_dereference(tsk->numa_group); |
| if (!grp) |
| goto no_join; |
| |
| my_grp = deref_curr_numa_group(p); |
| if (grp == my_grp) |
| goto no_join; |
| |
| /* |
| * Only join the other group if its bigger; if we're the bigger group, |
| * the other task will join us. |
| */ |
| if (my_grp->nr_tasks > grp->nr_tasks) |
| goto no_join; |
| |
| /* |
| * Tie-break on the grp address. |
| */ |
| if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) |
| goto no_join; |
| |
| /* Always join threads in the same process. */ |
| if (tsk->mm == current->mm) |
| join = true; |
| |
| /* Simple filter to avoid false positives due to PID collisions */ |
| if (flags & TNF_SHARED) |
| join = true; |
| |
| /* Update priv based on whether false sharing was detected */ |
| *priv = !join; |
| |
| if (join && !get_numa_group(grp)) |
| goto no_join; |
| |
| rcu_read_unlock(); |
| |
| if (!join) |
| return; |
| |
| BUG_ON(irqs_disabled()); |
| double_lock_irq(&my_grp->lock, &grp->lock); |
| |
| for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) { |
| my_grp->faults[i] -= p->numa_faults[i]; |
| grp->faults[i] += p->numa_faults[i]; |
| } |
| my_grp->total_faults -= p->total_numa_faults; |
| grp->total_faults += p->total_numa_faults; |
| |
| my_grp->nr_tasks--; |
| grp->nr_tasks++; |
| |
| spin_unlock(&my_grp->lock); |
| spin_unlock_irq(&grp->lock); |
| |
| rcu_assign_pointer(p->numa_group, grp); |
| |
| put_numa_group(my_grp); |
| return; |
| |
| no_join: |
| rcu_read_unlock(); |
| return; |
| } |
| |
| /* |
| * Get rid of NUMA staticstics associated with a task (either current or dead). |
| * If @final is set, the task is dead and has reached refcount zero, so we can |
| * safely free all relevant data structures. Otherwise, there might be |
| * concurrent reads from places like load balancing and procfs, and we should |
| * reset the data back to default state without freeing ->numa_faults. |
| */ |
| void task_numa_free(struct task_struct *p, bool final) |
| { |
| /* safe: p either is current or is being freed by current */ |
| struct numa_group *grp = rcu_dereference_raw(p->numa_group); |
| unsigned long *numa_faults = p->numa_faults; |
| unsigned long flags; |
| int i; |
| |
| if (!numa_faults) |
| return; |
| |
| if (grp) { |
| spin_lock_irqsave(&grp->lock, flags); |
| for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) |
| grp->faults[i] -= p->numa_faults[i]; |
| grp->total_faults -= p->total_numa_faults; |
| |
| grp->nr_tasks--; |
| spin_unlock_irqrestore(&grp->lock, flags); |
| RCU_INIT_POINTER(p->numa_group, NULL); |
| put_numa_group(grp); |
| } |
| |
| if (final) { |
| p->numa_faults = NULL; |
| kfree(numa_faults); |
| } else { |
| p->total_numa_faults = 0; |
| for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) |
| numa_faults[i] = 0; |
| } |
| } |
| |
| /* |
| * Got a PROT_NONE fault for a page on @node. |
| */ |
| void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) |
| { |
| struct task_struct *p = current; |
| bool migrated = flags & TNF_MIGRATED; |
| int cpu_node = task_node(current); |
| int local = !!(flags & TNF_FAULT_LOCAL); |
| struct numa_group *ng; |
| int priv; |
| |
| if (!static_branch_likely(&sched_numa_balancing)) |
| return; |
| |
| /* for example, ksmd faulting in a user's mm */ |
| if (!p->mm) |
| return; |
| |
| /* Allocate buffer to track faults on a per-node basis */ |
| if (unlikely(!p->numa_faults)) { |
| int size = sizeof(*p->numa_faults) * |
| NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids; |
| |
| p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN); |
| if (!p->numa_faults) |
| return; |
| |
| p->total_numa_faults = 0; |
| memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); |
| } |
| |
| /* |
| * First accesses are treated as private, otherwise consider accesses |
| * to be private if the accessing pid has not changed |
| */ |
| if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { |
| priv = 1; |
| } else { |
| priv = cpupid_match_pid(p, last_cpupid); |
| if (!priv && !(flags & TNF_NO_GROUP)) |
| task_numa_group(p, last_cpupid, flags, &priv); |
| } |
| |
| /* |
| * If a workload spans multiple NUMA nodes, a shared fault that |
| * occurs wholly within the set of nodes that the workload is |
| * actively using should be counted as local. This allows the |
| * scan rate to slow down when a workload has settled down. |
| */ |
| ng = deref_curr_numa_group(p); |
| if (!priv && !local && ng && ng->active_nodes > 1 && |
| numa_is_active_node(cpu_node, ng) && |
| numa_is_active_node(mem_node, ng)) |
| local = 1; |
| |
| /* |
| * Retry to migrate task to preferred node periodically, in case it |
| * previously failed, or the scheduler moved us. |
| */ |
| if (time_after(jiffies, p->numa_migrate_retry)) { |
| task_numa_placement(p); |
| numa_migrate_preferred(p); |
| } |
| |
| if (migrated) |
| p->numa_pages_migrated += pages; |
| if (flags & TNF_MIGRATE_FAIL) |
| p->numa_faults_locality[2] += pages; |
| |
| p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages; |
| p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages; |
| p->numa_faults_locality[local] += pages; |
| } |
| |
| static void reset_ptenuma_scan(struct task_struct *p) |
| { |
| /* |
| * We only did a read acquisition of the mmap sem, so |
| * p->mm->numa_scan_seq is written to without exclusive access |
| * and the update is not guaranteed to be atomic. That's not |
| * much of an issue though, since this is just used for |
| * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not |
| * expensive, to avoid any form of compiler optimizations: |
| */ |
| WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1); |
| p->mm->numa_scan_offset = 0; |
| } |
| |
| /* |
| * The expensive part of numa migration is done from task_work context. |
| * Triggered from task_tick_numa(). |
| */ |
| static void task_numa_work(struct callback_head *work) |
| { |
| unsigned long migrate, next_scan, now = jiffies; |
| struct task_struct *p = current; |
| struct mm_struct *mm = p->mm; |
| u64 runtime = p->se.sum_exec_runtime; |
| struct vm_area_struct *vma; |
| unsigned long start, end; |
| unsigned long nr_pte_updates = 0; |
| long pages, virtpages; |
| |
| SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work)); |
| |
| work->next = work; |
| /* |
| * Who cares about NUMA placement when they're dying. |
| * |
| * NOTE: make sure not to dereference p->mm before this check, |
| * exit_task_work() happens _after_ exit_mm() so we could be called |
| * without p->mm even though we still had it when we enqueued this |
| * work. |
| */ |
| if (p->flags & PF_EXITING) |
| return; |
| |
| if (!mm->numa_next_scan) { |
| mm->numa_next_scan = now + |
| msecs_to_jiffies(sysctl_numa_balancing_scan_delay); |
| } |
| |
| /* |
| * Enforce maximal scan/migration frequency.. |
| */ |
| migrate = mm->numa_next_scan; |
| if (time_before(now, migrate)) |
| return; |
| |
| if (p->numa_scan_period == 0) { |
| p->numa_scan_period_max = task_scan_max(p); |
| p->numa_scan_period = task_scan_start(p); |
| } |
| |
| next_scan = now + msecs_to_jiffies(p->numa_scan_period); |
| if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) |
| return; |
| |
| /* |
| * Delay this task enough that another task of this mm will likely win |
| * the next time around. |
| */ |
| p->node_stamp += 2 * TICK_NSEC; |
| |
| start = mm->numa_scan_offset; |
| pages = sysctl_numa_balancing_scan_size; |
| pages <<= 20 - PAGE_SHIFT; /* MB in pages */ |
| virtpages = pages * 8; /* Scan up to this much virtual space */ |
| if (!pages) |
| return; |
| |
| |
| if (!down_read_trylock(&mm->mmap_sem)) |
| return; |
| vma = find_vma(mm, start); |
| if (!vma) { |
| reset_ptenuma_scan(p); |
| start = 0; |
| vma = mm->mmap; |
| } |
| for (; vma; vma = vma->vm_next) { |
| if (!vma_migratable(vma) || !vma_policy_mof(vma) || |
| is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) { |
| continue; |
| } |
| |
| /* |
| * Shared library pages mapped by multiple processes are not |
| * migrated as it is expected they are cache replicated. Avoid |
| * hinting faults in read-only file-backed mappings or the vdso |
| * as migrating the pages will be of marginal benefit. |
| */ |
| if (!vma->vm_mm || |
| (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) |
| continue; |
| |
| /* |
| * Skip inaccessible VMAs to avoid any confusion between |
| * PROT_NONE and NUMA hinting ptes |
| */ |
| if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) |
| continue; |
| |
| do { |
| start = max(start, vma->vm_start); |
| end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); |
| end = min(end, vma->vm_end); |
| nr_pte_updates = change_prot_numa(vma, start, end); |
| |
| /* |
| * Try to scan sysctl_numa_balancing_size worth of |
| * hpages that have at least one present PTE that |
| * is not already pte-numa. If the VMA contains |
| * areas that are unused or already full of prot_numa |
| * PTEs, scan up to virtpages, to skip through those |
| * areas faster. |
| */ |
| if (nr_pte_updates) |
| pages -= (end - start) >> PAGE_SHIFT; |
| virtpages -= (end - start) >> PAGE_SHIFT; |
| |
| start = end; |
| if (pages <= 0 || virtpages <= 0) |
| goto out; |
| |
| cond_resched(); |
| } while (end != vma->vm_end); |
| } |
| |
| out: |
| /* |
| * It is possible to reach the end of the VMA list but the last few |
| * VMAs are not guaranteed to the vma_migratable. If they are not, we |
| * would find the !migratable VMA on the next scan but not reset the |
| * scanner to the start so check it now. |
| */ |
| if (vma) |
| mm->numa_scan_offset = start; |
| else |
| reset_ptenuma_scan(p); |
| up_read(&mm->mmap_sem); |
| |
| /* |
| * Make sure tasks use at least 32x as much time to run other code |
| * than they used here, to limit NUMA PTE scanning overhead to 3% max. |
| * Usually update_task_scan_period slows down scanning enough; on an |
| * overloaded system we need to limit overhead on a per task basis. |
| */ |
| if (unlikely(p->se.sum_exec_runtime != runtime)) { |
| u64 diff = p->se.sum_exec_runtime - runtime; |
| p->node_stamp += 32 * diff; |
| } |
| } |
| |
| void init_numa_balancing(unsigned long clone_flags, struct task_struct *p) |
| { |
| int mm_users = 0; |
| struct mm_struct *mm = p->mm; |
| |
| if (mm) { |
| mm_users = atomic_read(&mm->mm_users); |
| if (mm_users == 1) { |
| mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay); |
| mm->numa_scan_seq = 0; |
| } |
| } |
| p->node_stamp = 0; |
| p->numa_scan_seq = mm ? mm->numa_scan_seq : 0; |
| p->numa_scan_period = sysctl_numa_balancing_scan_delay; |
| /* Protect against double add, see task_tick_numa and task_numa_work */ |
| p->numa_work.next = &p->numa_work; |
| p->numa_faults = NULL; |
| RCU_INIT_POINTER(p->numa_group, NULL); |
| p->last_task_numa_placement = 0; |
| p->last_sum_exec_runtime = 0; |
| |
| init_task_work(&p->numa_work, task_numa_work); |
| |
| /* New address space, reset the preferred nid */ |
| if (!(clone_flags & CLONE_VM)) { |
| p->numa_preferred_nid = NUMA_NO_NODE; |
| return; |
| } |
| |
| /* |
| * New thread, keep existing numa_preferred_nid which should be copied |
| * already by arch_dup_task_struct but stagger when scans start. |
| */ |
| if (mm) { |
| unsigned int delay; |
| |
| delay = min_t(unsigned int, task_scan_max(current), |
| current->numa_scan_period * mm_users * NSEC_PER_MSEC); |
| delay += 2 * TICK_NSEC; |
| p->node_stamp = delay; |
| } |
| } |
| |
| /* |
| * Drive the periodic memory faults.. |
| */ |
| static void task_tick_numa(struct rq *rq, struct task_struct *curr) |
| { |
| struct callback_head *work = &curr->numa_work; |
| u64 period, now; |
| |
| /* |
| * We don't care about NUMA placement if we don't have memory. |
| */ |
| if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) |
| return; |
| |
| /* |
| * Using runtime rather than walltime has the dual advantage that |
| * we (mostly) drive the selection from busy threads and that the |
| * task needs to have done some actual work before we bother with |
| * NUMA placement. |
| */ |
| now = curr->se.sum_exec_runtime; |
| period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; |
| |
| if (now > curr->node_stamp + period) { |
| if (!curr->node_stamp) |
| curr->numa_scan_period = task_scan_start(curr); |
| curr->node_stamp += period; |
| |
| if (!time_before(jiffies, curr->mm->numa_next_scan)) |
| task_work_add(curr, work, true); |
| } |
| } |
| |
| static void update_scan_period(struct task_struct *p, int new_cpu) |
| { |
| int src_nid = cpu_to_node(task_cpu(p)); |
| int dst_nid = cpu_to_node(new_cpu); |
| |
| if (!static_branch_likely(&sched_numa_balancing)) |
| return; |
| |
| if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING)) |
| return; |
| |
| if (src_nid == dst_nid) |
| return; |
| |
| /* |
| * Allow resets if faults have been trapped before one scan |
| * has completed. This is most likely due to a new task that |
| * is pulled cross-node due to wakeups or load balancing. |
| */ |
| if (p->numa_scan_seq) { |
| /* |
| * Avoid scan adjustments if moving to the preferred |
| * node or if the task was not previously running on |
| * the preferred node. |
| */ |
| if (dst_nid == p->numa_preferred_nid || |
| (p->numa_preferred_nid != NUMA_NO_NODE && |
| src_nid != p->numa_preferred_nid)) |
| return; |
| } |
| |
| p->numa_scan_period = task_scan_start(p); |
| } |
| |
| #else |
| static void task_tick_numa(struct rq *rq, struct task_struct *curr) |
| { |
| } |
| |
| static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p) |
| { |
| } |
| |
| static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p) |
| { |
| } |
| |
| static inline void update_scan_period(struct task_struct *p, int new_cpu) |
| { |
| } |
| |
| #endif /* CONFIG_NUMA_BALANCING */ |
| |
| static void |
| account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| update_load_add(&cfs_rq->load, se->load.weight); |
| #ifdef CONFIG_SMP |
| if (entity_is_task(se)) { |
| struct rq *rq = rq_of(cfs_rq); |
| |
| account_numa_enqueue(rq, task_of(se)); |
| list_add(&se->group_node, &rq->cfs_tasks); |
| } |
| #endif |
| cfs_rq->nr_running++; |
| } |
| |
| static void |
| account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| update_load_sub(&cfs_rq->load, se->load.weight); |
| #ifdef CONFIG_SMP |
| if (entity_is_task(se)) { |
| account_numa_dequeue(rq_of(cfs_rq), task_of(se)); |
| list_del_init(&se->group_node); |
| } |
| #endif |
| cfs_rq->nr_running--; |
| } |
| |
| /* |
| * Signed add and clamp on underflow. |
| * |
| * Explicitly do a load-store to ensure the intermediate value never hits |
| * memory. This allows lockless observations without ever seeing the negative |
| * values. |
| */ |
| #define add_positive(_ptr, _val) do { \ |
| typeof(_ptr) ptr = (_ptr); \ |
| typeof(_val) val = (_val); \ |
| typeof(*ptr) res, var = READ_ONCE(*ptr); \ |
| \ |
| res = var + val; \ |
| \ |
| if (val < 0 && res > var) \ |
| res = 0; \ |
| \ |
| WRITE_ONCE(*ptr, res); \ |
| } while (0) |
| |
| /* |
| * Unsigned subtract and clamp on underflow. |
| * |
| * Explicitly do a load-store to ensure the intermediate value never hits |
| * memory. This allows lockless observations without ever seeing the negative |
| * values. |
| */ |
| #define sub_positive(_ptr, _val) do { \ |
| typeof(_ptr) ptr = (_ptr); \ |
| typeof(*ptr) val = (_val); \ |
| typeof(*ptr) res, var = READ_ONCE(*ptr); \ |
| res = var - val; \ |
| if (res > var) \ |
| res = 0; \ |
| WRITE_ONCE(*ptr, res); \ |
| } while (0) |
| |
| /* |
| * Remove and clamp on negative, from a local variable. |
| * |
| * A variant of sub_positive(), which does not use explicit load-store |
| * and is thus optimized for local variable updates. |
| */ |
| #define lsub_positive(_ptr, _val) do { \ |
| typeof(_ptr) ptr = (_ptr); \ |
| *ptr -= min_t(typeof(*ptr), *ptr, _val); \ |
| } while (0) |
| |
| #ifdef CONFIG_SMP |
| static inline void |
| enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| cfs_rq->runnable_weight += se->runnable_weight; |
| |
| cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg; |
| cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum; |
| } |
| |
| static inline void |
| dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| cfs_rq->runnable_weight -= se->runnable_weight; |
| |
| sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg); |
| sub_positive(&cfs_rq->avg.runnable_load_sum, |
| se_runnable(se) * se->avg.runnable_load_sum); |
| } |
| |
| static inline void |
| enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| cfs_rq->avg.load_avg += se->avg.load_avg; |
| cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum; |
| } |
| |
| static inline void |
| dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg); |
| sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum); |
| } |
| #else |
| static inline void |
| enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } |
| static inline void |
| dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } |
| static inline void |
| enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } |
| static inline void |
| dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { } |
| #endif |
| |
| static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, |
| unsigned long weight, unsigned long runnable) |
| { |
| if (se->on_rq) { |
| /* commit outstanding execution time */ |
| if (cfs_rq->curr == se) |
| update_curr(cfs_rq); |
| account_entity_dequeue(cfs_rq, se); |
| dequeue_runnable_load_avg(cfs_rq, se); |
| } |
| dequeue_load_avg(cfs_rq, se); |
| |
| se->runnable_weight = runnable; |
| update_load_set(&se->load, weight); |
| |
| #ifdef CONFIG_SMP |
| do { |
| u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib; |
| |
| se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider); |
| se->avg.runnable_load_avg = |
| div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider); |
| } while (0); |
| #endif |
| |
| enqueue_load_avg(cfs_rq, se); |
| if (se->on_rq) { |
| account_entity_enqueue(cfs_rq, se); |
| enqueue_runnable_load_avg(cfs_rq, se); |
| } |
| } |
| |
| void reweight_task(struct task_struct *p, int prio) |
| { |
| struct sched_entity *se = &p->se; |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| struct load_weight *load = &se->load; |
| unsigned long weight = scale_load(sched_prio_to_weight[prio]); |
| |
| reweight_entity(cfs_rq, se, weight, weight); |
| load->inv_weight = sched_prio_to_wmult[prio]; |
| } |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| #ifdef CONFIG_SMP |
| /* |
| * All this does is approximate the hierarchical proportion which includes that |
| * global sum we all love to hate. |
| * |
| * That is, the weight of a group entity, is the proportional share of the |
| * group weight based on the group runqueue weights. That is: |
| * |
| * tg->weight * grq->load.weight |
| * ge->load.weight = ----------------------------- (1) |
| * \Sum grq->load.weight |
| * |
| * Now, because computing that sum is prohibitively expensive to compute (been |
| * there, done that) we approximate it with this average stuff. The average |
| * moves slower and therefore the approximation is cheaper and more stable. |
| * |
| * So instead of the above, we substitute: |
| * |
| * grq->load.weight -> grq->avg.load_avg (2) |
| * |
| * which yields the following: |
| * |
| * tg->weight * grq->avg.load_avg |
| * ge->load.weight = ------------------------------ (3) |
| * tg->load_avg |
| * |
| * Where: tg->load_avg ~= \Sum grq->avg.load_avg |
| * |
| * That is shares_avg, and it is right (given the approximation (2)). |
| * |
| * The problem with it is that because the average is slow -- it was designed |
| * to be exactly that of course -- this leads to transients in boundary |
| * conditions. In specific, the case where the group was idle and we start the |
| * one task. It takes time for our CPU's grq->avg.load_avg to build up, |
| * yielding bad latency etc.. |
| * |
| * Now, in that special case (1) reduces to: |
| * |
| * tg->weight * grq->load.weight |
| * ge->load.weight = ----------------------------- = tg->weight (4) |
| * grp->load.weight |
| * |
| * That is, the sum collapses because all other CPUs are idle; the UP scenario. |
| * |
| * So what we do is modify our approximation (3) to approach (4) in the (near) |
| * UP case, like: |
| * |
| * ge->load.weight = |
| * |
| * tg->weight * grq->load.weight |
| * --------------------------------------------------- (5) |
| * tg->load_avg - grq->avg.load_avg + grq->load.weight |
| * |
| * But because grq->load.weight can drop to 0, resulting in a divide by zero, |
| * we need to use grq->avg.load_avg as its lower bound, which then gives: |
| * |
| * |
| * tg->weight * grq->load.weight |
| * ge->load.weight = ----------------------------- (6) |
| * tg_load_avg' |
| * |
| * Where: |
| * |
| * tg_load_avg' = tg->load_avg - grq->avg.load_avg + |
| * max(grq->load.weight, grq->avg.load_avg) |
| * |
| * And that is shares_weight and is icky. In the (near) UP case it approaches |
| * (4) while in the normal case it approaches (3). It consistently |
| * overestimates the ge->load.weight and therefore: |
| * |
| * \Sum ge->load.weight >= tg->weight |
| * |
| * hence icky! |
| */ |
| static long calc_group_shares(struct cfs_rq *cfs_rq) |
| { |
| long tg_weight, tg_shares, load, shares; |
| struct task_group *tg = cfs_rq->tg; |
| |
| tg_shares = READ_ONCE(tg->shares); |
| |
| load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg); |
| |
| tg_weight = atomic_long_read(&tg->load_avg); |
| |
| /* Ensure tg_weight >= load */ |
| tg_weight -= cfs_rq->tg_load_avg_contrib; |
| tg_weight += load; |
| |
| shares = (tg_shares * load); |
| if (tg_weight) |
| shares /= tg_weight; |
| |
| /* |
| * MIN_SHARES has to be unscaled here to support per-CPU partitioning |
| * of a group with small tg->shares value. It is a floor value which is |
| * assigned as a minimum load.weight to the sched_entity representing |
| * the group on a CPU. |
| * |
| * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024 |
| * on an 8-core system with 8 tasks each runnable on one CPU shares has |
| * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In |
| * case no task is runnable on a CPU MIN_SHARES=2 should be returned |
| * instead of 0. |
| */ |
| return clamp_t(long, shares, MIN_SHARES, tg_shares); |
| } |
| |
| /* |
| * This calculates the effective runnable weight for a group entity based on |
| * the group entity weight calculated above. |
| * |
| * Because of the above approximation (2), our group entity weight is |
| * an load_avg based ratio (3). This means that it includes blocked load and |
| * does not represent the runnable weight. |
| * |
| * Approximate the group entity's runnable weight per ratio from the group |
| * runqueue: |
| * |
| * grq->avg.runnable_load_avg |
| * ge->runnable_weight = ge->load.weight * -------------------------- (7) |
| * grq->avg.load_avg |
| * |
| * However, analogous to above, since the avg numbers are slow, this leads to |
| * transients in the from-idle case. Instead we use: |
| * |
| * ge->runnable_weight = ge->load.weight * |
| * |
| * max(grq->avg.runnable_load_avg, grq->runnable_weight) |
| * ----------------------------------------------------- (8) |
| * max(grq->avg.load_avg, grq->load.weight) |
| * |
| * Where these max() serve both to use the 'instant' values to fix the slow |
| * from-idle and avoid the /0 on to-idle, similar to (6). |
| */ |
| static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares) |
| { |
| long runnable, load_avg; |
| |
| load_avg = max(cfs_rq->avg.load_avg, |
| scale_load_down(cfs_rq->load.weight)); |
| |
| runnable = max(cfs_rq->avg.runnable_load_avg, |
| scale_load_down(cfs_rq->runnable_weight)); |
| |
| runnable *= shares; |
| if (load_avg) |
| runnable /= load_avg; |
| |
| return clamp_t(long, runnable, MIN_SHARES, shares); |
| } |
| #endif /* CONFIG_SMP */ |
| |
| static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); |
| |
| /* |
| * Recomputes the group entity based on the current state of its group |
| * runqueue. |
| */ |
| static void update_cfs_group(struct sched_entity *se) |
| { |
| struct cfs_rq *gcfs_rq = group_cfs_rq(se); |
| long shares, runnable; |
| |
| if (!gcfs_rq) |
| return; |
| |
| if (throttled_hierarchy(gcfs_rq)) |
| return; |
| |
| #ifndef CONFIG_SMP |
| runnable = shares = READ_ONCE(gcfs_rq->tg->shares); |
| |
| if (likely(se->load.weight == shares)) |
| return; |
| #else |
| shares = calc_group_shares(gcfs_rq); |
| runnable = calc_group_runnable(gcfs_rq, shares); |
| #endif |
| |
| reweight_entity(cfs_rq_of(se), se, shares, runnable); |
| } |
| |
| #else /* CONFIG_FAIR_GROUP_SCHED */ |
| static inline void update_cfs_group(struct sched_entity *se) |
| { |
| } |
| #endif /* CONFIG_FAIR_GROUP_SCHED */ |
| |
| static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags) |
| { |
| struct rq *rq = rq_of(cfs_rq); |
| |
| if (&rq->cfs == cfs_rq) { |
| /* |
| * There are a few boundary cases this might miss but it should |
| * get called often enough that that should (hopefully) not be |
| * a real problem. |
| * |
| * It will not get called when we go idle, because the idle |
| * thread is a different class (!fair), nor will the utilization |
| * number include things like RT tasks. |
| * |
| * As is, the util number is not freq-invariant (we'd have to |
| * implement arch_scale_freq_capacity() for that). |
| * |
| * See cpu_util(). |
| */ |
| cpufreq_update_util(rq, flags); |
| } |
| } |
| |
| #ifdef CONFIG_SMP |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| /** |
| * update_tg_load_avg - update the tg's load avg |
| * @cfs_rq: the cfs_rq whose avg changed |
| * @force: update regardless of how small the difference |
| * |
| * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load. |
| * However, because tg->load_avg is a global value there are performance |
| * considerations. |
| * |
| * In order to avoid having to look at the other cfs_rq's, we use a |
| * differential update where we store the last value we propagated. This in |
| * turn allows skipping updates if the differential is 'small'. |
| * |
| * Updating tg's load_avg is necessary before update_cfs_share(). |
| */ |
| static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) |
| { |
| long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib; |
| |
| /* |
| * No need to update load_avg for root_task_group as it is not used. |
| */ |
| if (cfs_rq->tg == &root_task_group) |
| return; |
| |
| if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) { |
| atomic_long_add(delta, &cfs_rq->tg->load_avg); |
| cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg; |
| } |
| } |
| |
| /* |
| * Called within set_task_rq() right before setting a task's CPU. The |
| * caller only guarantees p->pi_lock is held; no other assumptions, |
| * including the state of rq->lock, should be made. |
| */ |
| void set_task_rq_fair(struct sched_entity *se, |
| struct cfs_rq *prev, struct cfs_rq *next) |
| { |
| u64 p_last_update_time; |
| u64 n_last_update_time; |
| |
| if (!sched_feat(ATTACH_AGE_LOAD)) |
| return; |
| |
| /* |
| * We are supposed to update the task to "current" time, then its up to |
| * date and ready to go to new CPU/cfs_rq. But we have difficulty in |
| * getting what current time is, so simply throw away the out-of-date |
| * time. This will result in the wakee task is less decayed, but giving |
| * the wakee more load sounds not bad. |
| */ |
| if (!(se->avg.last_update_time && prev)) |
| return; |
| |
| #ifndef CONFIG_64BIT |
| { |
| u64 p_last_update_time_copy; |
| u64 n_last_update_time_copy; |
| |
| do { |
| p_last_update_time_copy = prev->load_last_update_time_copy; |
| n_last_update_time_copy = next->load_last_update_time_copy; |
| |
| smp_rmb(); |
| |
| p_last_update_time = prev->avg.last_update_time; |
| n_last_update_time = next->avg.last_update_time; |
| |
| } while (p_last_update_time != p_last_update_time_copy || |
| n_last_update_time != n_last_update_time_copy); |
| } |
| #else |
| p_last_update_time = prev->avg.last_update_time; |
| n_last_update_time = next->avg.last_update_time; |
| #endif |
| __update_load_avg_blocked_se(p_last_update_time, se); |
| se->avg.last_update_time = n_last_update_time; |
| } |
| |
| |
| /* |
| * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to |
| * propagate its contribution. The key to this propagation is the invariant |
| * that for each group: |
| * |
| * ge->avg == grq->avg (1) |
| * |
| * _IFF_ we look at the pure running and runnable sums. Because they |
| * represent the very same entity, just at different points in the hierarchy. |
| * |
| * Per the above update_tg_cfs_util() is trivial and simply copies the running |
| * sum over (but still wrong, because the group entity and group rq do not have |
| * their PELT windows aligned). |
| * |
| * However, update_tg_cfs_runnable() is more complex. So we have: |
| * |
| * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2) |
| * |
| * And since, like util, the runnable part should be directly transferable, |
| * the following would _appear_ to be the straight forward approach: |
| * |
| * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3) |
| * |
| * And per (1) we have: |
| * |
| * ge->avg.runnable_avg == grq->avg.runnable_avg |
| * |
| * Which gives: |
| * |
| * ge->load.weight * grq->avg.load_avg |
| * ge->avg.load_avg = ----------------------------------- (4) |
| * grq->load.weight |
| * |
| * Except that is wrong! |
| * |
| * Because while for entities historical weight is not important and we |
| * really only care about our future and therefore can consider a pure |
| * runnable sum, runqueues can NOT do this. |
| * |
| * We specifically want runqueues to have a load_avg that includes |
| * historical weights. Those represent the blocked load, the load we expect |
| * to (shortly) return to us. This only works by keeping the weights as |
| * integral part of the sum. We therefore cannot decompose as per (3). |
| * |
| * Another reason this doesn't work is that runnable isn't a 0-sum entity. |
| * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the |
| * rq itself is runnable anywhere between 2/3 and 1 depending on how the |
| * runnable section of these tasks overlap (or not). If they were to perfectly |
| * align the rq as a whole would be runnable 2/3 of the time. If however we |
| * always have at least 1 runnable task, the rq as a whole is always runnable. |
| * |
| * So we'll have to approximate.. :/ |
| * |
| * Given the constraint: |
| * |
| * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX |
| * |
| * We can construct a rule that adds runnable to a rq by assuming minimal |
| * overlap. |
| * |
| * On removal, we'll assume each task is equally runnable; which yields: |
| * |
| * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight |
| * |
| * XXX: only do this for the part of runnable > running ? |
| * |
| */ |
| |
| static inline void |
| update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) |
| { |
| long delta = gcfs_rq->avg.util_avg - se->avg.util_avg; |
| |
| /* Nothing to update */ |
| if (!delta) |
| return; |
| |
| /* |
| * The relation between sum and avg is: |
| * |
| * LOAD_AVG_MAX - 1024 + sa->period_contrib |
| * |
| * however, the PELT windows are not aligned between grq and gse. |
| */ |
| |
| /* Set new sched_entity's utilization */ |
| se->avg.util_avg = gcfs_rq->avg.util_avg; |
| se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX; |
| |
| /* Update parent cfs_rq utilization */ |
| add_positive(&cfs_rq->avg.util_avg, delta); |
| cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX; |
| } |
| |
| static inline void |
| update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) |
| { |
| long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum; |
| unsigned long runnable_load_avg, load_avg; |
| u64 runnable_load_sum, load_sum = 0; |
| s64 delta_sum; |
| |
| if (!runnable_sum) |
| return; |
| |
| gcfs_rq->prop_runnable_sum = 0; |
| |
| if (runnable_sum >= 0) { |
| /* |
| * Add runnable; clip at LOAD_AVG_MAX. Reflects that until |
| * the CPU is saturated running == runnable. |
| */ |
| runnable_sum += se->avg.load_sum; |
| runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX); |
| } else { |
| /* |
| * Estimate the new unweighted runnable_sum of the gcfs_rq by |
| * assuming all tasks are equally runnable. |
| */ |
| if (scale_load_down(gcfs_rq->load.weight)) { |
| load_sum = div_s64(gcfs_rq->avg.load_sum, |
| scale_load_down(gcfs_rq->load.weight)); |
| } |
| |
| /* But make sure to not inflate se's runnable */ |
| runnable_sum = min(se->avg.load_sum, load_sum); |
| } |
| |
| /* |
| * runnable_sum can't be lower than running_sum |
| * Rescale running sum to be in the same range as runnable sum |
| * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT] |
| * runnable_sum is in [0 : LOAD_AVG_MAX] |
| */ |
| running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT; |
| runnable_sum = max(runnable_sum, running_sum); |
| |
| load_sum = (s64)se_weight(se) * runnable_sum; |
| load_avg = div_s64(load_sum, LOAD_AVG_MAX); |
| |
| delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum; |
| delta_avg = load_avg - se->avg.load_avg; |
| |
| se->avg.load_sum = runnable_sum; |
| se->avg.load_avg = load_avg; |
| add_positive(&cfs_rq->avg.load_avg, delta_avg); |
| add_positive(&cfs_rq->avg.load_sum, delta_sum); |
| |
| runnable_load_sum = (s64)se_runnable(se) * runnable_sum; |
| runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX); |
| |
| if (se->on_rq) { |
| delta_sum = runnable_load_sum - |
| se_weight(se) * se->avg.runnable_load_sum; |
| delta_avg = runnable_load_avg - se->avg.runnable_load_avg; |
| add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg); |
| add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum); |
| } |
| |
| se->avg.runnable_load_sum = runnable_sum; |
| se->avg.runnable_load_avg = runnable_load_avg; |
| } |
| |
| static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) |
| { |
| cfs_rq->propagate = 1; |
| cfs_rq->prop_runnable_sum += runnable_sum; |
| } |
| |
| /* Update task and its cfs_rq load average */ |
| static inline int propagate_entity_load_avg(struct sched_entity *se) |
| { |
| struct cfs_rq *cfs_rq, *gcfs_rq; |
| |
| if (entity_is_task(se)) |
| return 0; |
| |
| gcfs_rq = group_cfs_rq(se); |
| if (!gcfs_rq->propagate) |
| return 0; |
| |
| gcfs_rq->propagate = 0; |
| |
| cfs_rq = cfs_rq_of(se); |
| |
| add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum); |
| |
| update_tg_cfs_util(cfs_rq, se, gcfs_rq); |
| update_tg_cfs_runnable(cfs_rq, se, gcfs_rq); |
| |
| trace_pelt_cfs_tp(cfs_rq); |
| trace_pelt_se_tp(se); |
| |
| return 1; |
| } |
| |
| /* |
| * Check if we need to update the load and the utilization of a blocked |
| * group_entity: |
| */ |
| static inline bool skip_blocked_update(struct sched_entity *se) |
| { |
| struct cfs_rq *gcfs_rq = group_cfs_rq(se); |
| |
| /* |
| * If sched_entity still have not zero load or utilization, we have to |
| * decay it: |
| */ |
| if (se->avg.load_avg || se->avg.util_avg) |
| return false; |
| |
| /* |
| * If there is a pending propagation, we have to update the load and |
| * the utilization of the sched_entity: |
| */ |
| if (gcfs_rq->propagate) |
| return false; |
| |
| /* |
| * Otherwise, the load and the utilization of the sched_entity is |
| * already zero and there is no pending propagation, so it will be a |
| * waste of time to try to decay it: |
| */ |
| return true; |
| } |
| |
| #else /* CONFIG_FAIR_GROUP_SCHED */ |
| |
| static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {} |
| |
| static inline int propagate_entity_load_avg(struct sched_entity *se) |
| { |
| return 0; |
| } |
| |
| static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {} |
| |
| #endif /* CONFIG_FAIR_GROUP_SCHED */ |
| |
| /** |
| * update_cfs_rq_load_avg - update the cfs_rq's load/util averages |
| * @now: current time, as per cfs_rq_clock_pelt() |
| * @cfs_rq: cfs_rq to update |
| * |
| * The cfs_rq avg is the direct sum of all its entities (blocked and runnable) |
| * avg. The immediate corollary is that all (fair) tasks must be attached, see |
| * post_init_entity_util_avg(). |
| * |
| * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example. |
| * |
| * Returns true if the load decayed or we removed load. |
| * |
| * Since both these conditions indicate a changed cfs_rq->avg.load we should |
| * call update_tg_load_avg() when this function returns true. |
| */ |
| static inline int |
| update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) |
| { |
| unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0; |
| struct sched_avg *sa = &cfs_rq->avg; |
| int decayed = 0; |
| |
| if (cfs_rq->removed.nr) { |
| unsigned long r; |
| u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib; |
| |
| raw_spin_lock(&cfs_rq->removed.lock); |
| swap(cfs_rq->removed.util_avg, removed_util); |
| swap(cfs_rq->removed.load_avg, removed_load); |
| swap(cfs_rq->removed.runnable_sum, removed_runnable_sum); |
| cfs_rq->removed.nr = 0; |
| raw_spin_unlock(&cfs_rq->removed.lock); |
| |
| r = removed_load; |
| sub_positive(&sa->load_avg, r); |
| sub_positive(&sa->load_sum, r * divider); |
| |
| r = removed_util; |
| sub_positive(&sa->util_avg, r); |
| sub_positive(&sa->util_sum, r * divider); |
| |
| add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum); |
| |
| decayed = 1; |
| } |
| |
| decayed |= __update_load_avg_cfs_rq(now, cfs_rq); |
| |
| #ifndef CONFIG_64BIT |
| smp_wmb(); |
| cfs_rq->load_last_update_time_copy = sa->last_update_time; |
| #endif |
| |
| return decayed; |
| } |
| |
| /** |
| * attach_entity_load_avg - attach this entity to its cfs_rq load avg |
| * @cfs_rq: cfs_rq to attach to |
| * @se: sched_entity to attach |
| * @flags: migration hints |
| * |
| * Must call update_cfs_rq_load_avg() before this, since we rely on |
| * cfs_rq->avg.last_update_time being current. |
| */ |
| static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib; |
| |
| /* |
| * When we attach the @se to the @cfs_rq, we must align the decay |
| * window because without that, really weird and wonderful things can |
| * happen. |
| * |
| * XXX illustrate |
| */ |
| se->avg.last_update_time = cfs_rq->avg.last_update_time; |
| se->avg.period_contrib = cfs_rq->avg.period_contrib; |
| |
| /* |
| * Hell(o) Nasty stuff.. we need to recompute _sum based on the new |
| * period_contrib. This isn't strictly correct, but since we're |
| * entirely outside of the PELT hierarchy, nobody cares if we truncate |
| * _sum a little. |
| */ |
| se->avg.util_sum = se->avg.util_avg * divider; |
| |
| se->avg.load_sum = divider; |
| if (se_weight(se)) { |
| se->avg.load_sum = |
| div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se)); |
| } |
| |
| se->avg.runnable_load_sum = se->avg.load_sum; |
| |
| enqueue_load_avg(cfs_rq, se); |
| cfs_rq->avg.util_avg += se->avg.util_avg; |
| cfs_rq->avg.util_sum += se->avg.util_sum; |
| |
| add_tg_cfs_propagate(cfs_rq, se->avg.load_sum); |
| |
| cfs_rq_util_change(cfs_rq, 0); |
| |
| trace_pelt_cfs_tp(cfs_rq); |
| } |
| |
| /** |
| * detach_entity_load_avg - detach this entity from its cfs_rq load avg |
| * @cfs_rq: cfs_rq to detach from |
| * @se: sched_entity to detach |
| * |
| * Must call update_cfs_rq_load_avg() before this, since we rely on |
| * cfs_rq->avg.last_update_time being current. |
| */ |
| static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| dequeue_load_avg(cfs_rq, se); |
| sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg); |
| sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum); |
| |
| add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum); |
| |
| cfs_rq_util_change(cfs_rq, 0); |
| |
| trace_pelt_cfs_tp(cfs_rq); |
| } |
| |
| /* |
| * Optional action to be done while updating the load average |
| */ |
| #define UPDATE_TG 0x1 |
| #define SKIP_AGE_LOAD 0x2 |
| #define DO_ATTACH 0x4 |
| |
| /* Update task and its cfs_rq load average */ |
| static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) |
| { |
| u64 now = cfs_rq_clock_pelt(cfs_rq); |
| int decayed; |
| |
| /* |
| * Track task load average for carrying it to new CPU after migrated, and |
| * track group sched_entity load average for task_h_load calc in migration |
| */ |
| if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD)) |
| __update_load_avg_se(now, cfs_rq, se); |
| |
| decayed = update_cfs_rq_load_avg(now, cfs_rq); |
| decayed |= propagate_entity_load_avg(se); |
| |
| if (!se->avg.last_update_time && (flags & DO_ATTACH)) { |
| |
| /* |
| * DO_ATTACH means we're here from enqueue_entity(). |
| * !last_update_time means we've passed through |
| * migrate_task_rq_fair() indicating we migrated. |
| * |
| * IOW we're enqueueing a task on a new CPU. |
| */ |
| attach_entity_load_avg(cfs_rq, se); |
| update_tg_load_avg(cfs_rq, 0); |
| |
| } else if (decayed) { |
| cfs_rq_util_change(cfs_rq, 0); |
| |
| if (flags & UPDATE_TG) |
| update_tg_load_avg(cfs_rq, 0); |
| } |
| } |
| |
| #ifndef CONFIG_64BIT |
| static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) |
| { |
| u64 last_update_time_copy; |
| u64 last_update_time; |
| |
| do { |
| last_update_time_copy = cfs_rq->load_last_update_time_copy; |
| smp_rmb(); |
| last_update_time = cfs_rq->avg.last_update_time; |
| } while (last_update_time != last_update_time_copy); |
| |
| return last_update_time; |
| } |
| #else |
| static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) |
| { |
| return cfs_rq->avg.last_update_time; |
| } |
| #endif |
| |
| /* |
| * Synchronize entity load avg of dequeued entity without locking |
| * the previous rq. |
| */ |
| static void sync_entity_load_avg(struct sched_entity *se) |
| { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| u64 last_update_time; |
| |
| last_update_time = cfs_rq_last_update_time(cfs_rq); |
| __update_load_avg_blocked_se(last_update_time, se); |
| } |
| |
| /* |
| * Task first catches up with cfs_rq, and then subtract |
| * itself from the cfs_rq (task must be off the queue now). |
| */ |
| static void remove_entity_load_avg(struct sched_entity *se) |
| { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| unsigned long flags; |
| |
| /* |
| * tasks cannot exit without having gone through wake_up_new_task() -> |
| * post_init_entity_util_avg() which will have added things to the |
| * cfs_rq, so we can remove unconditionally. |
| */ |
| |
| sync_entity_load_avg(se); |
| |
| raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags); |
| ++cfs_rq->removed.nr; |
| cfs_rq->removed.util_avg += se->avg.util_avg; |
| cfs_rq->removed.load_avg += se->avg.load_avg; |
| cfs_rq->removed.runnable_sum += se->avg.load_sum; /* == runnable_sum */ |
| raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags); |
| } |
| |
| static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq) |
| { |
| return cfs_rq->avg.runnable_load_avg; |
| } |
| |
| static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq) |
| { |
| return cfs_rq->avg.load_avg; |
| } |
| |
| static inline unsigned long task_util(struct task_struct *p) |
| { |
| return READ_ONCE(p->se.avg.util_avg); |
| } |
| |
| static inline unsigned long _task_util_est(struct task_struct *p) |
| { |
| struct util_est ue = READ_ONCE(p->se.avg.util_est); |
| |
| return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED); |
| } |
| |
| static inline unsigned long task_util_est(struct task_struct *p) |
| { |
| return max(task_util(p), _task_util_est(p)); |
| } |
| |
| #ifdef CONFIG_UCLAMP_TASK |
| static inline unsigned long uclamp_task_util(struct task_struct *p) |
| { |
| return clamp(task_util_est(p), |
| uclamp_eff_value(p, UCLAMP_MIN), |
| uclamp_eff_value(p, UCLAMP_MAX)); |
| } |
| #else |
| static inline unsigned long uclamp_task_util(struct task_struct *p) |
| { |
| return task_util_est(p); |
| } |
| #endif |
| |
| static inline void util_est_enqueue(struct cfs_rq *cfs_rq, |
| struct task_struct *p) |
| { |
| unsigned int enqueued; |
| |
| if (!sched_feat(UTIL_EST)) |
| return; |
| |
| /* Update root cfs_rq's estimated utilization */ |
| enqueued = cfs_rq->avg.util_est.enqueued; |
| enqueued += _task_util_est(p); |
| WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); |
| } |
| |
| /* |
| * Check if a (signed) value is within a specified (unsigned) margin, |
| * based on the observation that: |
| * |
| * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1) |
| * |
| * NOTE: this only works when value + maring < INT_MAX. |
| */ |
| static inline bool within_margin(int value, int margin) |
| { |
| return ((unsigned int)(value + margin - 1) < (2 * margin - 1)); |
| } |
| |
| static void |
| util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) |
| { |
| long last_ewma_diff; |
| struct util_est ue; |
| int cpu; |
| |
| if (!sched_feat(UTIL_EST)) |
| return; |
| |
| /* Update root cfs_rq's estimated utilization */ |
| ue.enqueued = cfs_rq->avg.util_est.enqueued; |
| ue.enqueued -= min_t(unsigned int, ue.enqueued, _task_util_est(p)); |
| WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued); |
| |
| /* |
| * Skip update of task's estimated utilization when the task has not |
| * yet completed an activation, e.g. being migrated. |
| */ |
| if (!task_sleep) |
| return; |
| |
| /* |
| * If the PELT values haven't changed since enqueue time, |
| * skip the util_est update. |
| */ |
| ue = p->se.avg.util_est; |
| if (ue.enqueued & UTIL_AVG_UNCHANGED) |
| return; |
| |
| /* |
| * Reset EWMA on utilization increases, the moving average is used only |
| * to smooth utilization decreases. |
| */ |
| ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED); |
| if (sched_feat(UTIL_EST_FASTUP)) { |
| if (ue.ewma < ue.enqueued) { |
| ue.ewma = ue.enqueued; |
| goto done; |
| } |
| } |
| |
| /* |
| * Skip update of task's estimated utilization when its EWMA is |
| * already ~1% close to its last activation value. |
| */ |
| last_ewma_diff = ue.enqueued - ue.ewma; |
| if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100))) |
| return; |
| |
| /* |
| * To avoid overestimation of actual task utilization, skip updates if |
| * we cannot grant there is idle time in this CPU. |
| */ |
| cpu = cpu_of(rq_of(cfs_rq)); |
| if (task_util(p) > capacity_orig_of(cpu)) |
| return; |
| |
| /* |
| * Update Task's estimated utilization |
| * |
| * When *p completes an activation we can consolidate another sample |
| * of the task size. This is done by storing the current PELT value |
| * as ue.enqueued and by using this value to update the Exponential |
| * Weighted Moving Average (EWMA): |
| * |
| * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1) |
| * = w * task_util(p) + ewma(t-1) - w * ewma(t-1) |
| * = w * (task_util(p) - ewma(t-1)) + ewma(t-1) |
| * = w * ( last_ewma_diff ) + ewma(t-1) |
| * = w * (last_ewma_diff + ewma(t-1) / w) |
| * |
| * Where 'w' is the weight of new samples, which is configured to be |
| * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT) |
| */ |
| ue.ewma <<= UTIL_EST_WEIGHT_SHIFT; |
| ue.ewma += last_ewma_diff; |
| ue.ewma >>= UTIL_EST_WEIGHT_SHIFT; |
| done: |
| WRITE_ONCE(p->se.avg.util_est, ue); |
| } |
| |
| static inline int task_fits_capacity(struct task_struct *p, long capacity) |
| { |
| return fits_capacity(uclamp_task_util(p), capacity); |
| } |
| |
| static inline void update_misfit_status(struct task_struct *p, struct rq *rq) |
| { |
| if (!static_branch_unlikely(&sched_asym_cpucapacity)) |
| return; |
| |
| if (!p) { |
| rq->misfit_task_load = 0; |
| return; |
| } |
| |
| if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) { |
| rq->misfit_task_load = 0; |
| return; |
| } |
| |
| rq->misfit_task_load = task_h_load(p); |
| } |
| |
| #else /* CONFIG_SMP */ |
| |
| #define UPDATE_TG 0x0 |
| #define SKIP_AGE_LOAD 0x0 |
| #define DO_ATTACH 0x0 |
| |
| static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1) |
| { |
| cfs_rq_util_change(cfs_rq, 0); |
| } |
| |
| static inline void remove_entity_load_avg(struct sched_entity *se) {} |
| |
| static inline void |
| attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} |
| static inline void |
| detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} |
| |
| static inline int idle_balance(struct rq *rq, struct rq_flags *rf) |
| { |
| return 0; |
| } |
| |
| static inline void |
| util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {} |
| |
| static inline void |
| util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, |
| bool task_sleep) {} |
| static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {} |
| |
| #endif /* CONFIG_SMP */ |
| |
| static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| #ifdef CONFIG_SCHED_DEBUG |
| s64 d = se->vruntime - cfs_rq->min_vruntime; |
| |
| if (d < 0) |
| d = -d; |
| |
| if (d > 3*sysctl_sched_latency) |
| schedstat_inc(cfs_rq->nr_spread_over); |
| #endif |
| } |
| |
| static void |
| place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) |
| { |
| u64 vruntime = cfs_rq->min_vruntime; |
| |
| /* |
| * The 'current' period is already promised to the current tasks, |
| * however the extra weight of the new task will slow them down a |
| * little, place the new task so that it fits in the slot that |
| * stays open at the end. |
| */ |
| if (initial && sched_feat(START_DEBIT)) |
| vruntime += sched_vslice(cfs_rq, se); |
| |
| /* sleeps up to a single latency don't count. */ |
| if (!initial) { |
| unsigned long thresh = sysctl_sched_latency; |
| |
| /* |
| * Halve their sleep time's effect, to allow |
| * for a gentler effect of sleepers: |
| */ |
| if (sched_feat(GENTLE_FAIR_SLEEPERS)) |
| thresh >>= 1; |
| |
| vruntime -= thresh; |
| } |
| |
| /* ensure we never gain time by being placed backwards. */ |
| se->vruntime = max_vruntime(se->vruntime, vruntime); |
| } |
| |
| static void check_enqueue_throttle(struct cfs_rq *cfs_rq); |
| |
| static inline void check_schedstat_required(void) |
| { |
| #ifdef CONFIG_SCHEDSTATS |
| if (schedstat_enabled()) |
| return; |
| |
| /* Force schedstat enabled if a dependent tracepoint is active */ |
| if (trace_sched_stat_wait_enabled() || |
| trace_sched_stat_sleep_enabled() || |
| trace_sched_stat_iowait_enabled() || |
| trace_sched_stat_blocked_enabled() || |
| trace_sched_stat_runtime_enabled()) { |
| printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, " |
| "stat_blocked and stat_runtime require the " |
| "kernel parameter schedstats=enable or " |
| "kernel.sched_schedstats=1\n"); |
| } |
| #endif |
| } |
| |
| |
| /* |
| * MIGRATION |
| * |
| * dequeue |
| * update_curr() |
| * update_min_vruntime() |
| * vruntime -= min_vruntime |
| * |
| * enqueue |
| * update_curr() |
| * update_min_vruntime() |
| * vruntime += min_vruntime |
| * |
| * this way the vruntime transition between RQs is done when both |
| * min_vruntime are up-to-date. |
| * |
| * WAKEUP (remote) |
| * |
| * ->migrate_task_rq_fair() (p->state == TASK_WAKING) |
| * vruntime -= min_vruntime |
| * |
| * enqueue |
| * update_curr() |
| * update_min_vruntime() |
| * vruntime += min_vruntime |
| * |
| * this way we don't have the most up-to-date min_vruntime on the originating |
| * CPU and an up-to-date min_vruntime on the destination CPU. |
| */ |
| |
| static void |
| enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) |
| { |
| bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED); |
| bool curr = cfs_rq->curr == se; |
| |
| /* |
| * If we're the current task, we must renormalise before calling |
| * update_curr(). |
| */ |
| if (renorm && curr) |
| se->vruntime += cfs_rq->min_vruntime; |
| |
| update_curr(cfs_rq); |
| |
| /* |
| * Otherwise, renormalise after, such that we're placed at the current |
| * moment in time, instead of some random moment in the past. Being |
| * placed in the past could significantly boost this task to the |
| * fairness detriment of existing tasks. |
| */ |
| if (renorm && !curr) |
| se->vruntime += cfs_rq->min_vruntime; |
| |
| /* |
| * When enqueuing a sched_entity, we must: |
| * - Update loads to have both entity and cfs_rq synced with now. |
| * - Add its load to cfs_rq->runnable_avg |
| * - For group_entity, update its weight to reflect the new share of |
| * its group cfs_rq |
| * - Add its new weight to cfs_rq->load.weight |
| */ |
| update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH); |
| update_cfs_group(se); |
| enqueue_runnable_load_avg(cfs_rq, se); |
| account_entity_enqueue(cfs_rq, se); |
| |
| if (flags & ENQUEUE_WAKEUP) |
| place_entity(cfs_rq, se, 0); |
| |
| check_schedstat_required(); |
| update_stats_enqueue(cfs_rq, se, flags); |
| check_spread(cfs_rq, se); |
| if (!curr) |
| __enqueue_entity(cfs_rq, se); |
| se->on_rq = 1; |
| |
| if (cfs_rq->nr_running == 1) { |
| list_add_leaf_cfs_rq(cfs_rq); |
| check_enqueue_throttle(cfs_rq); |
| } |
| } |
| |
| static void __clear_buddies_last(struct sched_entity *se) |
| { |
| for_each_sched_entity(se) { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| if (cfs_rq->last != se) |
| break; |
| |
| cfs_rq->last = NULL; |
| } |
| } |
| |
| static void __clear_buddies_next(struct sched_entity *se) |
| { |
| for_each_sched_entity(se) { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| if (cfs_rq->next != se) |
| break; |
| |
| cfs_rq->next = NULL; |
| } |
| } |
| |
| static void __clear_buddies_skip(struct sched_entity *se) |
| { |
| for_each_sched_entity(se) { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| if (cfs_rq->skip != se) |
| break; |
| |
| cfs_rq->skip = NULL; |
| } |
| } |
| |
| static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| if (cfs_rq->last == se) |
| __clear_buddies_last(se); |
| |
| if (cfs_rq->next == se) |
| __clear_buddies_next(se); |
| |
| if (cfs_rq->skip == se) |
| __clear_buddies_skip(se); |
| } |
| |
| static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); |
| |
| static void |
| dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) |
| { |
| /* |
| * Update run-time statistics of the 'current'. |
| */ |
| update_curr(cfs_rq); |
| |
| /* |
| * When dequeuing a sched_entity, we must: |
| * - Update loads to have both entity and cfs_rq synced with now. |
| * - Subtract its load from the cfs_rq->runnable_avg. |
| * - Subtract its previous weight from cfs_rq->load.weight. |
| * - For group entity, update its weight to reflect the new share |
| * of its group cfs_rq. |
| */ |
| update_load_avg(cfs_rq, se, UPDATE_TG); |
| dequeue_runnable_load_avg(cfs_rq, se); |
| |
| update_stats_dequeue(cfs_rq, se, flags); |
| |
| clear_buddies(cfs_rq, se); |
| |
| if (se != cfs_rq->curr) |
| __dequeue_entity(cfs_rq, se); |
| se->on_rq = 0; |
| account_entity_dequeue(cfs_rq, se); |
| |
| /* |
| * Normalize after update_curr(); which will also have moved |
| * min_vruntime if @se is the one holding it back. But before doing |
| * update_min_vruntime() again, which will discount @se's position and |
| * can move min_vruntime forward still more. |
| */ |
| if (!(flags & DEQUEUE_SLEEP)) |
| se->vruntime -= cfs_rq->min_vruntime; |
| |
| /* return excess runtime on last dequeue */ |
| return_cfs_rq_runtime(cfs_rq); |
| |
| update_cfs_group(se); |
| |
| /* |
| * Now advance min_vruntime if @se was the entity holding it back, |
| * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be |
| * put back on, and if we advance min_vruntime, we'll be placed back |
| * further than we started -- ie. we'll be penalized. |
| */ |
| if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE) |
| update_min_vruntime(cfs_rq); |
| } |
| |
| /* |
| * Preempt the current task with a newly woken task if needed: |
| */ |
| static void |
| check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) |
| { |
| unsigned long ideal_runtime, delta_exec; |
| struct sched_entity *se; |
| s64 delta; |
| |
| ideal_runtime = sched_slice(cfs_rq, curr); |
| delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; |
| if (delta_exec > ideal_runtime) { |
| resched_curr(rq_of(cfs_rq)); |
| /* |
| * The current task ran long enough, ensure it doesn't get |
| * re-elected due to buddy favours. |
| */ |
| clear_buddies(cfs_rq, curr); |
| return; |
| } |
| |
| /* |
| * Ensure that a task that missed wakeup preemption by a |
| * narrow margin doesn't have to wait for a full slice. |
| * This also mitigates buddy induced latencies under load. |
| */ |
| if (delta_exec < sysctl_sched_min_granularity) |
| return; |
| |
| se = __pick_first_entity(cfs_rq); |
| delta = curr->vruntime - se->vruntime; |
| |
| if (delta < 0) |
| return; |
| |
| if (delta > ideal_runtime) |
| resched_curr(rq_of(cfs_rq)); |
| } |
| |
| static void |
| set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) |
| { |
| /* 'current' is not kept within the tree. */ |
| if (se->on_rq) { |
| /* |
| * Any task has to be enqueued before it get to execute on |
| * a CPU. So account for the time it spent waiting on the |
| * runqueue. |
| */ |
| update_stats_wait_end(cfs_rq, se); |
| __dequeue_entity(cfs_rq, se); |
| update_load_avg(cfs_rq, se, UPDATE_TG); |
| } |
| |
| update_stats_curr_start(cfs_rq, se); |
| cfs_rq->curr = se; |
| |
| /* |
| * Track our maximum slice length, if the CPU's load is at |
| * least twice that of our own weight (i.e. dont track it |
| * when there are only lesser-weight tasks around): |
| */ |
| if (schedstat_enabled() && |
| rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) { |
| schedstat_set(se->statistics.slice_max, |
| max((u64)schedstat_val(se->statistics.slice_max), |
| se->sum_exec_runtime - se->prev_sum_exec_runtime)); |
| } |
| |
| se->prev_sum_exec_runtime = se->sum_exec_runtime; |
| } |
| |
| static int |
| wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); |
| |
| /* |
| * Pick the next process, keeping these things in mind, in this order: |
| * 1) keep things fair between processes/task groups |
| * 2) pick the "next" process, since someone really wants that to run |
| * 3) pick the "last" process, for cache locality |
| * 4) do not run the "skip" process, if something else is available |
| */ |
| static struct sched_entity * |
| pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) |
| { |
| struct sched_entity *left = __pick_first_entity(cfs_rq); |
| struct sched_entity *se; |
| |
| /* |
| * If curr is set we have to see if its left of the leftmost entity |
| * still in the tree, provided there was anything in the tree at all. |
| */ |
| if (!left || (curr && entity_before(curr, left))) |
| left = curr; |
| |
| se = left; /* ideally we run the leftmost entity */ |
| |
| /* |
| * Avoid running the skip buddy, if running something else can |
| * be done without getting too unfair. |
| */ |
| if (cfs_rq->skip == se) { |
| struct sched_entity *second; |
| |
| if (se == curr) { |
| second = __pick_first_entity(cfs_rq); |
| } else { |
| second = __pick_next_entity(se); |
| if (!second || (curr && entity_before(curr, second))) |
| second = curr; |
| } |
| |
| if (second && wakeup_preempt_entity(second, left) < 1) |
| se = second; |
| } |
| |
| /* |
| * Prefer last buddy, try to return the CPU to a preempted task. |
| */ |
| if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) |
| se = cfs_rq->last; |
| |
| /* |
| * Someone really wants this to run. If it's not unfair, run it. |
| */ |
| if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) |
| se = cfs_rq->next; |
| |
| clear_buddies(cfs_rq, se); |
| |
| return se; |
| } |
| |
| static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq); |
| |
| static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) |
| { |
| /* |
| * If still on the runqueue then deactivate_task() |
| * was not called and update_curr() has to be done: |
| */ |
| if (prev->on_rq) |
| update_curr(cfs_rq); |
| |
| /* throttle cfs_rqs exceeding runtime */ |
| check_cfs_rq_runtime(cfs_rq); |
| |
| check_spread(cfs_rq, prev); |
| |
| if (prev->on_rq) { |
| update_stats_wait_start(cfs_rq, prev); |
| /* Put 'current' back into the tree. */ |
| __enqueue_entity(cfs_rq, prev); |
| /* in !on_rq case, update occurred at dequeue */ |
| update_load_avg(cfs_rq, prev, 0); |
| } |
| cfs_rq->curr = NULL; |
| } |
| |
| static void |
| entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) |
| { |
| /* |
| * Update run-time statistics of the 'current'. |
| */ |
| update_curr(cfs_rq); |
| |
| /* |
| * Ensure that runnable average is periodically updated. |
| */ |
| update_load_avg(cfs_rq, curr, UPDATE_TG); |
| update_cfs_group(curr); |
| |
| #ifdef CONFIG_SCHED_HRTICK |
| /* |
| * queued ticks are scheduled to match the slice, so don't bother |
| * validating it and just reschedule. |
| */ |
| if (queued) { |
| resched_curr(rq_of(cfs_rq)); |
| return; |
| } |
| /* |
| * don't let the period tick interfere with the hrtick preemption |
| */ |
| if (!sched_feat(DOUBLE_TICK) && |
| hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) |
| return; |
| #endif |
| |
| if (cfs_rq->nr_running > 1) |
| check_preempt_tick(cfs_rq, curr); |
| } |
| |
| |
| /************************************************** |
| * CFS bandwidth control machinery |
| */ |
| |
| #ifdef CONFIG_CFS_BANDWIDTH |
| |
| #ifdef CONFIG_JUMP_LABEL |
| static struct static_key __cfs_bandwidth_used; |
| |
| static inline bool cfs_bandwidth_used(void) |
| { |
| return static_key_false(&__cfs_bandwidth_used); |
| } |
| |
| void cfs_bandwidth_usage_inc(void) |
| { |
| static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used); |
| } |
| |
| void cfs_bandwidth_usage_dec(void) |
| { |
| static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used); |
| } |
| #else /* CONFIG_JUMP_LABEL */ |
| static bool cfs_bandwidth_used(void) |
| { |
| return true; |
| } |
| |
| void cfs_bandwidth_usage_inc(void) {} |
| void cfs_bandwidth_usage_dec(void) {} |
| #endif /* CONFIG_JUMP_LABEL */ |
| |
| /* |
| * default period for cfs group bandwidth. |
| * default: 0.1s, units: nanoseconds |
| */ |
| static inline u64 default_cfs_period(void) |
| { |
| return 100000000ULL; |
| } |
| |
| static inline u64 sched_cfs_bandwidth_slice(void) |
| { |
| return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; |
| } |
| |
| /* |
| * Replenish runtime according to assigned quota. We use sched_clock_cpu |
| * directly instead of rq->clock to avoid adding additional synchronization |
| * around rq->lock. |
| * |
| * requires cfs_b->lock |
| */ |
| void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) |
| { |
| if (cfs_b->quota != RUNTIME_INF) |
| cfs_b->runtime = cfs_b->quota; |
| } |
| |
| static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) |
| { |
| return &tg->cfs_bandwidth; |
| } |
| |
| /* returns 0 on failure to allocate runtime */ |
| static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) |
| { |
| struct task_group *tg = cfs_rq->tg; |
| struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); |
| u64 amount = 0, min_amount; |
| |
| /* note: this is a positive sum as runtime_remaining <= 0 */ |
| min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; |
| |
| raw_spin_lock(&cfs_b->lock); |
| if (cfs_b->quota == RUNTIME_INF) |
| amount = min_amount; |
| else { |
| start_cfs_bandwidth(cfs_b); |
| |
| if (cfs_b->runtime > 0) { |
| amount = min(cfs_b->runtime, min_amount); |
| cfs_b->runtime -= amount; |
| cfs_b->idle = 0; |
| } |
| } |
| raw_spin_unlock(&cfs_b->lock); |
| |
| cfs_rq->runtime_remaining += amount; |
| |
| return cfs_rq->runtime_remaining > 0; |
| } |
| |
| static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) |
| { |
| /* dock delta_exec before expiring quota (as it could span periods) */ |
| cfs_rq->runtime_remaining -= delta_exec; |
| |
| if (likely(cfs_rq->runtime_remaining > 0)) |
| return; |
| |
| if (cfs_rq->throttled) |
| return; |
| /* |
| * if we're unable to extend our runtime we resched so that the active |
| * hierarchy can be throttled |
| */ |
| if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) |
| resched_curr(rq_of(cfs_rq)); |
| } |
| |
| static __always_inline |
| void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) |
| { |
| if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) |
| return; |
| |
| __account_cfs_rq_runtime(cfs_rq, delta_exec); |
| } |
| |
| static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) |
| { |
| return cfs_bandwidth_used() && cfs_rq->throttled; |
| } |
| |
| /* check whether cfs_rq, or any parent, is throttled */ |
| static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) |
| { |
| return cfs_bandwidth_used() && cfs_rq->throttle_count; |
| } |
| |
| /* |
| * Ensure that neither of the group entities corresponding to src_cpu or |
| * dest_cpu are members of a throttled hierarchy when performing group |
| * load-balance operations. |
| */ |
| static inline int throttled_lb_pair(struct task_group *tg, |
| int src_cpu, int dest_cpu) |
| { |
| struct cfs_rq *src_cfs_rq, *dest_cfs_rq; |
| |
| src_cfs_rq = tg->cfs_rq[src_cpu]; |
| dest_cfs_rq = tg->cfs_rq[dest_cpu]; |
| |
| return throttled_hierarchy(src_cfs_rq) || |
| throttled_hierarchy(dest_cfs_rq); |
| } |
| |
| static int tg_unthrottle_up(struct task_group *tg, void *data) |
| { |
| struct rq *rq = data; |
| struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; |
| |
| cfs_rq->throttle_count--; |
| if (!cfs_rq->throttle_count) { |
| cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - |
| cfs_rq->throttled_clock_task; |
| |
| /* Add cfs_rq with already running entity in the list */ |
| if (cfs_rq->nr_running >= 1) |
| list_add_leaf_cfs_rq(cfs_rq); |
| } |
| |
| return 0; |
| } |
| |
| static int tg_throttle_down(struct task_group *tg, void *data) |
| { |
| struct rq *rq = data; |
| struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; |
| |
| /* group is entering throttled state, stop time */ |
| if (!cfs_rq->throttle_count) { |
| cfs_rq->throttled_clock_task = rq_clock_task(rq); |
| list_del_leaf_cfs_rq(cfs_rq); |
| } |
| cfs_rq->throttle_count++; |
| |
| return 0; |
| } |
| |
| static void throttle_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| struct rq *rq = rq_of(cfs_rq); |
| struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); |
| struct sched_entity *se; |
| long task_delta, idle_task_delta, dequeue = 1; |
| bool empty; |
| |
| se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; |
| |
| /* freeze hierarchy runnable averages while throttled */ |
| rcu_read_lock(); |
| walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); |
| rcu_read_unlock(); |
| |
| task_delta = cfs_rq->h_nr_running; |
| idle_task_delta = cfs_rq->idle_h_nr_running; |
| for_each_sched_entity(se) { |
| struct cfs_rq *qcfs_rq = cfs_rq_of(se); |
| /* throttled entity or throttle-on-deactivate */ |
| if (!se->on_rq) |
| break; |
| |
| if (dequeue) |
| dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); |
| qcfs_rq->h_nr_running -= task_delta; |
| qcfs_rq->idle_h_nr_running -= idle_task_delta; |
| |
| if (qcfs_rq->load.weight) |
| dequeue = 0; |
| } |
| |
| if (!se) |
| sub_nr_running(rq, task_delta); |
| |
| cfs_rq->throttled = 1; |
| cfs_rq->throttled_clock = rq_clock(rq); |
| raw_spin_lock(&cfs_b->lock); |
| empty = list_empty(&cfs_b->throttled_cfs_rq); |
| |
| /* |
| * Add to the _head_ of the list, so that an already-started |
| * distribute_cfs_runtime will not see us. If disribute_cfs_runtime is |
| * not running add to the tail so that later runqueues don't get starved. |
| */ |
| if (cfs_b->distribute_running) |
| list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); |
| else |
| list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); |
| |
| /* |
| * If we're the first throttled task, make sure the bandwidth |
| * timer is running. |
| */ |
| if (empty) |
| start_cfs_bandwidth(cfs_b); |
| |
| raw_spin_unlock(&cfs_b->lock); |
| } |
| |
| void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| struct rq *rq = rq_of(cfs_rq); |
| struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); |
| struct sched_entity *se; |
| int enqueue = 1; |
| long task_delta, idle_task_delta; |
| |
| se = cfs_rq->tg->se[cpu_of(rq)]; |
| |
| cfs_rq->throttled = 0; |
| |
| update_rq_clock(rq); |
| |
| raw_spin_lock(&cfs_b->lock); |
| cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; |
| list_del_rcu(&cfs_rq->throttled_list); |
| raw_spin_unlock(&cfs_b->lock); |
| |
| /* update hierarchical throttle state */ |
| walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); |
| |
| if (!cfs_rq->load.weight) |
| return; |
| |
| task_delta = cfs_rq->h_nr_running; |
| idle_task_delta = cfs_rq->idle_h_nr_running; |
| for_each_sched_entity(se) { |
| if (se->on_rq) |
| enqueue = 0; |
| |
| cfs_rq = cfs_rq_of(se); |
| if (enqueue) |
| enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); |
| cfs_rq->h_nr_running += task_delta; |
| cfs_rq->idle_h_nr_running += idle_task_delta; |
| |
| if (cfs_rq_throttled(cfs_rq)) |
| break; |
| } |
| |
| assert_list_leaf_cfs_rq(rq); |
| |
| if (!se) |
| add_nr_running(rq, task_delta); |
| |
| /* Determine whether we need to wake up potentially idle CPU: */ |
| if (rq->curr == rq->idle && rq->cfs.nr_running) |
| resched_curr(rq); |
| } |
| |
| static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, u64 remaining) |
| { |
| struct cfs_rq *cfs_rq; |
| u64 runtime; |
| u64 starting_runtime = remaining; |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, |
| throttled_list) { |
| struct rq *rq = rq_of(cfs_rq); |
| struct rq_flags rf; |
| |
| rq_lock_irqsave(rq, &rf); |
| if (!cfs_rq_throttled(cfs_rq)) |
| goto next; |
| |
| /* By the above check, this should never be true */ |
| SCHED_WARN_ON(cfs_rq->runtime_remaining > 0); |
| |
| runtime = -cfs_rq->runtime_remaining + 1; |
| if (runtime > remaining) |
| runtime = remaining; |
| remaining -= runtime; |
| |
| cfs_rq->runtime_remaining += runtime; |
| |
| /* we check whether we're throttled above */ |
| if (cfs_rq->runtime_remaining > 0) |
| unthrottle_cfs_rq(cfs_rq); |
| |
| next: |
| rq_unlock_irqrestore(rq, &rf); |
| |
| if (!remaining) |
| break; |
| } |
| rcu_read_unlock(); |
| |
| return starting_runtime - remaining; |
| } |
| |
| /* |
| * Responsible for refilling a task_group's bandwidth and unthrottling its |
| * cfs_rqs as appropriate. If there has been no activity within the last |
| * period the timer is deactivated until scheduling resumes; cfs_b->idle is |
| * used to track this state. |
| */ |
| static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags) |
| { |
| u64 runtime; |
| int throttled; |
| |
| /* no need to continue the timer with no bandwidth constraint */ |
| if (cfs_b->quota == RUNTIME_INF) |
| goto out_deactivate; |
| |
| throttled = !list_empty(&cfs_b->throttled_cfs_rq); |
| cfs_b->nr_periods += overrun; |
| |
| /* |
| * idle depends on !throttled (for the case of a large deficit), and if |
| * we're going inactive then everything else can be deferred |
| */ |
| if (cfs_b->idle && !throttled) |
| goto out_deactivate; |
| |
| __refill_cfs_bandwidth_runtime(cfs_b); |
| |
| if (!throttled) { |
| /* mark as potentially idle for the upcoming period */ |
| cfs_b->idle = 1; |
| return 0; |
| } |
| |
| /* account preceding periods in which throttling occurred */ |
| cfs_b->nr_throttled += overrun; |
| |
| /* |
| * This check is repeated as we are holding onto the new bandwidth while |
| * we unthrottle. This can potentially race with an unthrottled group |
| * trying to acquire new bandwidth from the global pool. This can result |
| * in us over-using our runtime if it is all used during this loop, but |
| * only by limited amounts in that extreme case. |
| */ |
| while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) { |
| runtime = cfs_b->runtime; |
| cfs_b->distribute_running = 1; |
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags); |
| /* we can't nest cfs_b->lock while distributing bandwidth */ |
| runtime = distribute_cfs_runtime(cfs_b, runtime); |
| raw_spin_lock_irqsave(&cfs_b->lock, flags); |
| |
| cfs_b->distribute_running = 0; |
| throttled = !list_empty(&cfs_b->throttled_cfs_rq); |
| |
| lsub_positive(&cfs_b->runtime, runtime); |
| } |
| |
| /* |
| * While we are ensured activity in the period following an |
| * unthrottle, this also covers the case in which the new bandwidth is |
| * insufficient to cover the existing bandwidth deficit. (Forcing the |
| * timer to remain active while there are any throttled entities.) |
| */ |
| cfs_b->idle = 0; |
| |
| return 0; |
| |
| out_deactivate: |
| return 1; |
| } |
| |
| /* a cfs_rq won't donate quota below this amount */ |
| static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; |
| /* minimum remaining period time to redistribute slack quota */ |
| static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; |
| /* how long we wait to gather additional slack before distributing */ |
| static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; |
| |
| /* |
| * Are we near the end of the current quota period? |
| * |
| * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the |
| * hrtimer base being cleared by hrtimer_start. In the case of |
| * migrate_hrtimers, base is never cleared, so we are fine. |
| */ |
| static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) |
| { |
| struct hrtimer *refresh_timer = &cfs_b->period_timer; |
| u64 remaining; |
| |
| /* if the call-back is running a quota refresh is already occurring */ |
| if (hrtimer_callback_running(refresh_timer)) |
| return 1; |
| |
| /* is a quota refresh about to occur? */ |
| remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); |
| if (remaining < min_expire) |
| return 1; |
| |
| return 0; |
| } |
| |
| static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) |
| { |
| u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; |
| |
| /* if there's a quota refresh soon don't bother with slack */ |
| if (runtime_refresh_within(cfs_b, min_left)) |
| return; |
| |
| /* don't push forwards an existing deferred unthrottle */ |
| if (cfs_b->slack_started) |
| return; |
| cfs_b->slack_started = true; |
| |
| hrtimer_start(&cfs_b->slack_timer, |
| ns_to_ktime(cfs_bandwidth_slack_period), |
| HRTIMER_MODE_REL); |
| } |
| |
| /* we know any runtime found here is valid as update_curr() precedes return */ |
| static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) |
| { |
| struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); |
| s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; |
| |
| if (slack_runtime <= 0) |
| return; |
| |
| raw_spin_lock(&cfs_b->lock); |
| if (cfs_b->quota != RUNTIME_INF) { |
| cfs_b->runtime += slack_runtime; |
| |
| /* we are under rq->lock, defer unthrottling using a timer */ |
| if (cfs_b->runtime > sched_cfs_bandwidth_slice() && |
| !list_empty(&cfs_b->throttled_cfs_rq)) |
| start_cfs_slack_bandwidth(cfs_b); |
| } |
| raw_spin_unlock(&cfs_b->lock); |
| |
| /* even if it's not valid for return we don't want to try again */ |
| cfs_rq->runtime_remaining -= slack_runtime; |
| } |
| |
| static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) |
| { |
| if (!cfs_bandwidth_used()) |
| return; |
| |
| if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) |
| return; |
| |
| __return_cfs_rq_runtime(cfs_rq); |
| } |
| |
| /* |
| * This is done with a timer (instead of inline with bandwidth return) since |
| * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. |
| */ |
| static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) |
| { |
| u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); |
| unsigned long flags; |
| |
| /* confirm we're still not at a refresh boundary */ |
| raw_spin_lock_irqsave(&cfs_b->lock, flags); |
| cfs_b->slack_started = false; |
| if (cfs_b->distribute_running) { |
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags); |
| return; |
| } |
| |
| if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { |
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags); |
| return; |
| } |
| |
| if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) |
| runtime = cfs_b->runtime; |
| |
| if (runtime) |
| cfs_b->distribute_running = 1; |
| |
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags); |
| |
| if (!runtime) |
| return; |
| |
| runtime = distribute_cfs_runtime(cfs_b, runtime); |
| |
| raw_spin_lock_irqsave(&cfs_b->lock, flags); |
| lsub_positive(&cfs_b->runtime, runtime); |
| cfs_b->distribute_running = 0; |
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags); |
| } |
| |
| /* |
| * When a group wakes up we want to make sure that its quota is not already |
| * expired/exceeded, otherwise it may be allowed to steal additional ticks of |
| * runtime as update_curr() throttling can not not trigger until it's on-rq. |
| */ |
| static void check_enqueue_throttle(struct cfs_rq *cfs_rq) |
| { |
| if (!cfs_bandwidth_used()) |
| return; |
| |
| /* an active group must be handled by the update_curr()->put() path */ |
| if (!cfs_rq->runtime_enabled || cfs_rq->curr) |
| return; |
| |
| /* ensure the group is not already throttled */ |
| if (cfs_rq_throttled(cfs_rq)) |
| return; |
| |
| /* update runtime allocation */ |
| account_cfs_rq_runtime(cfs_rq, 0); |
| if (cfs_rq->runtime_remaining <= 0) |
| throttle_cfs_rq(cfs_rq); |
| } |
| |
| static void sync_throttle(struct task_group *tg, int cpu) |
| { |
| struct cfs_rq *pcfs_rq, *cfs_rq; |
| |
| if (!cfs_bandwidth_used()) |
| return; |
| |
| if (!tg->parent) |
| return; |
| |
| cfs_rq = tg->cfs_rq[cpu]; |
| pcfs_rq = tg->parent->cfs_rq[cpu]; |
| |
| cfs_rq->throttle_count = pcfs_rq->throttle_count; |
| cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu)); |
| } |
| |
| /* conditionally throttle active cfs_rq's from put_prev_entity() */ |
| static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) |
| { |
| if (!cfs_bandwidth_used()) |
| return false; |
| |
| if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) |
| return false; |
| |
| /* |
| * it's possible for a throttled entity to be forced into a running |
| * state (e.g. set_curr_task), in this case we're finished. |
| */ |
| if (cfs_rq_throttled(cfs_rq)) |
| return true; |
| |
| throttle_cfs_rq(cfs_rq); |
| return true; |
| } |
| |
| static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) |
| { |
| struct cfs_bandwidth *cfs_b = |
| container_of(timer, struct cfs_bandwidth, slack_timer); |
| |
| do_sched_cfs_slack_timer(cfs_b); |
| |
| return HRTIMER_NORESTART; |
| } |
| |
| extern const u64 max_cfs_quota_period; |
| |
| static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) |
| { |
| struct cfs_bandwidth *cfs_b = |
| container_of(timer, struct cfs_bandwidth, period_timer); |
| unsigned long flags; |
| int overrun; |
| int idle = 0; |
| int count = 0; |
| |
| raw_spin_lock_irqsave(&cfs_b->lock, flags); |
| for (;;) { |
| overrun = hrtimer_forward_now(timer, cfs_b->period); |
| if (!overrun) |
| break; |
| |
| if (++count > 3) { |
| u64 new, old = ktime_to_ns(cfs_b->period); |
| |
| /* |
| * Grow period by a factor of 2 to avoid losing precision. |
| * Precision loss in the quota/period ratio can cause __cfs_schedulable |
| * to fail. |
| */ |
| new = old * 2; |
| if (new < max_cfs_quota_period) { |
| cfs_b->period = ns_to_ktime(new); |
| cfs_b->quota *= 2; |
| |
| pr_warn_ratelimited( |
| "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n", |
| smp_processor_id(), |
| div_u64(new, NSEC_PER_USEC), |
| div_u64(cfs_b->quota, NSEC_PER_USEC)); |
| } else { |
| pr_warn_ratelimited( |
| "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n", |
| smp_processor_id(), |
| div_u64(old, NSEC_PER_USEC), |
| div_u64(cfs_b->quota, NSEC_PER_USEC)); |
| } |
| |
| /* reset count so we don't come right back in here */ |
| count = 0; |
| } |
| |
| idle = do_sched_cfs_period_timer(cfs_b, overrun, flags); |
| } |
| if (idle) |
| cfs_b->period_active = 0; |
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags); |
| |
| return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; |
| } |
| |
| void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) |
| { |
| raw_spin_lock_init(&cfs_b->lock); |
| cfs_b->runtime = 0; |
| cfs_b->quota = RUNTIME_INF; |
| cfs_b->period = ns_to_ktime(default_cfs_period()); |
| |
| INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); |
| hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); |
| cfs_b->period_timer.function = sched_cfs_period_timer; |
| hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); |
| cfs_b->slack_timer.function = sched_cfs_slack_timer; |
| cfs_b->distribute_running = 0; |
| cfs_b->slack_started = false; |
| } |
| |
| static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) |
| { |
| cfs_rq->runtime_enabled = 0; |
| INIT_LIST_HEAD(&cfs_rq->throttled_list); |
| } |
| |
| void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) |
| { |
| lockdep_assert_held(&cfs_b->lock); |
| |
| if (cfs_b->period_active) |
| return; |
| |
| cfs_b->period_active = 1; |
| hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); |
| hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); |
| } |
| |
| static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) |
| { |
| /* init_cfs_bandwidth() was not called */ |
| if (!cfs_b->throttled_cfs_rq.next) |
| return; |
| |
| hrtimer_cancel(&cfs_b->period_timer); |
| hrtimer_cancel(&cfs_b->slack_timer); |
| } |
| |
| /* |
| * Both these CPU hotplug callbacks race against unregister_fair_sched_group() |
| * |
| * The race is harmless, since modifying bandwidth settings of unhooked group |
| * bits doesn't do much. |
| */ |
| |
| /* cpu online calback */ |
| static void __maybe_unused update_runtime_enabled(struct rq *rq) |
| { |
| struct task_group *tg; |
| |
| lockdep_assert_held(&rq->lock); |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(tg, &task_groups, list) { |
| struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; |
| struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; |
| |
| raw_spin_lock(&cfs_b->lock); |
| cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; |
| raw_spin_unlock(&cfs_b->lock); |
| } |
| rcu_read_unlock(); |
| } |
| |
| /* cpu offline callback */ |
| static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) |
| { |
| struct task_group *tg; |
| |
| lockdep_assert_held(&rq->lock); |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(tg, &task_groups, list) { |
| struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; |
| |
| if (!cfs_rq->runtime_enabled) |
| continue; |
| |
| /* |
| * clock_task is not advancing so we just need to make sure |
| * there's some valid quota amount |
| */ |
| cfs_rq->runtime_remaining = 1; |
| /* |
| * Offline rq is schedulable till CPU is completely disabled |
| * in take_cpu_down(), so we prevent new cfs throttling here. |
| */ |
| cfs_rq->runtime_enabled = 0; |
| |
| if (cfs_rq_throttled(cfs_rq)) |
| unthrottle_cfs_rq(cfs_rq); |
| } |
| rcu_read_unlock(); |
| } |
| |
| #else /* CONFIG_CFS_BANDWIDTH */ |
| |
| static inline bool cfs_bandwidth_used(void) |
| { |
| return false; |
| } |
| |
| static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} |
| static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } |
| static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} |
| static inline void sync_throttle(struct task_group *tg, int cpu) {} |
| static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} |
| |
| static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) |
| { |
| return 0; |
| } |
| |
| static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) |
| { |
| return 0; |
| } |
| |
| static inline int throttled_lb_pair(struct task_group *tg, |
| int src_cpu, int dest_cpu) |
| { |
| return 0; |
| } |
| |
| void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} |
| #endif |
| |
| static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) |
| { |
| return NULL; |
| } |
| static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} |
| static inline void update_runtime_enabled(struct rq *rq) {} |
| static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} |
| |
| #endif /* CONFIG_CFS_BANDWIDTH */ |
| |
| /************************************************** |
| * CFS operations on tasks: |
| */ |
| |
| #ifdef CONFIG_SCHED_HRTICK |
| static void hrtick_start_fair(struct rq *rq, struct task_struct *p) |
| { |
| struct sched_entity *se = &p->se; |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| |
| SCHED_WARN_ON(task_rq(p) != rq); |
| |
| if (rq->cfs.h_nr_running > 1) { |
| u64 slice = sched_slice(cfs_rq, se); |
| u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; |
| s64 delta = slice - ran; |
| |
| if (delta < 0) { |
| if (rq->curr == p) |
| resched_curr(rq); |
| return; |
| } |
| hrtick_start(rq, delta); |
| } |
| } |
| |
| /* |
| * called from enqueue/dequeue and updates the hrtick when the |
| * current task is from our class and nr_running is low enough |
| * to matter. |
| */ |
| static void hrtick_update(struct rq *rq) |
| { |
| struct task_struct *curr = rq->curr; |
| |
| if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) |
| return; |
| |
| if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) |
| hrtick_start_fair(rq, curr); |
| } |
| #else /* !CONFIG_SCHED_HRTICK */ |
| static inline void |
| hrtick_start_fair(struct rq *rq, struct task_struct *p) |
| { |
| } |
| |
| static inline void hrtick_update(struct rq *rq) |
| { |
| } |
| #endif |
| |
| #ifdef CONFIG_SMP |
| static inline unsigned long cpu_util(int cpu); |
| |
| static inline bool cpu_overutilized(int cpu) |
| { |
| return !fits_capacity(cpu_util(cpu), capacity_of(cpu)); |
| } |
| |
| static inline void update_overutilized_status(struct rq *rq) |
| { |
| if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) { |
| WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED); |
| trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED); |
| } |
| } |
| #else |
| static inline void update_overutilized_status(struct rq *rq) { } |
| #endif |
| |
| /* Runqueue only has SCHED_IDLE tasks enqueued */ |
| static int sched_idle_rq(struct rq *rq) |
| { |
| return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running && |
| rq->nr_running); |
| } |
| |
| #ifdef CONFIG_SMP |
| static int sched_idle_cpu(int cpu) |
| { |
| return sched_idle_rq(cpu_rq(cpu)); |
| } |
| #endif |
| |
| /* |
| * The enqueue_task method is called before nr_running is |
| * increased. Here we update the fair scheduling stats and |
| * then put the task into the rbtree: |
| */ |
| static void |
| enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) |
| { |
| struct cfs_rq *cfs_rq; |
| struct sched_entity *se = &p->se; |
| int idle_h_nr_running = task_has_idle_policy(p); |
| |
| /* |
| * The code below (indirectly) updates schedutil which looks at |
| * the cfs_rq utilization to select a frequency. |
| * Let's add the task's estimated utilization to the cfs_rq's |
| * estimated utilization, before we update schedutil. |
| */ |
| util_est_enqueue(&rq->cfs, p); |
| |
| /* |
| * If in_iowait is set, the code below may not trigger any cpufreq |
| * utilization updates, so do it here explicitly with the IOWAIT flag |
| * passed. |
| */ |
| if (p->in_iowait) |
| cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT); |
| |
| for_each_sched_entity(se) { |
| if (se->on_rq) |
| break; |
| cfs_rq = cfs_rq_of(se); |
| enqueue_entity(cfs_rq, se, flags); |
| |
| /* |
| * end evaluation on encountering a throttled cfs_rq |
| * |
| * note: in the case of encountering a throttled cfs_rq we will |
| * post the final h_nr_running increment below. |
| */ |
| if (cfs_rq_throttled(cfs_rq)) |
| break; |
| cfs_rq->h_nr_running++; |
| cfs_rq->idle_h_nr_running += idle_h_nr_running; |
| |
| flags = ENQUEUE_WAKEUP; |
| } |
| |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| cfs_rq->h_nr_running++; |
| cfs_rq->idle_h_nr_running += idle_h_nr_running; |
| |
| if (cfs_rq_throttled(cfs_rq)) |
| break; |
| |
| update_load_avg(cfs_rq, se, UPDATE_TG); |
| update_cfs_group(se); |
| } |
| |
| if (!se) { |
| add_nr_running(rq, 1); |
| /* |
| * Since new tasks are assigned an initial util_avg equal to |
| * half of the spare capacity of their CPU, tiny tasks have the |
| * ability to cross the overutilized threshold, which will |
| * result in the load balancer ruining all the task placement |
| * done by EAS. As a way to mitigate that effect, do not account |
| * for the first enqueue operation of new tasks during the |
| * overutilized flag detection. |
| * |
| * A better way of solving this problem would be to wait for |
| * the PELT signals of tasks to converge before taking them |
| * into account, but that is not straightforward to implement, |
| * and the following generally works well enough in practice. |
| */ |
| if (flags & ENQUEUE_WAKEUP) |
| update_overutilized_status(rq); |
| |
| } |
| |
| if (cfs_bandwidth_used()) { |
| /* |
| * When bandwidth control is enabled; the cfs_rq_throttled() |
| * breaks in the above iteration can result in incomplete |
| * leaf list maintenance, resulting in triggering the assertion |
| * below. |
| */ |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| |
| if (list_add_leaf_cfs_rq(cfs_rq)) |
| break; |
| } |
| } |
| |
| assert_list_leaf_cfs_rq(rq); |
| |
| hrtick_update(rq); |
| } |
| |
| static void set_next_buddy(struct sched_entity *se); |
| |
| /* |
| * The dequeue_task method is called before nr_running is |
| * decreased. We remove the task from the rbtree and |
| * update the fair scheduling stats: |
| */ |
| static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) |
| { |
| struct cfs_rq *cfs_rq; |
| struct sched_entity *se = &p->se; |
| int task_sleep = flags & DEQUEUE_SLEEP; |
| int idle_h_nr_running = task_has_idle_policy(p); |
| bool was_sched_idle = sched_idle_rq(rq); |
| |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| dequeue_entity(cfs_rq, se, flags); |
| |
| /* |
| * end evaluation on encountering a throttled cfs_rq |
| * |
| * note: in the case of encountering a throttled cfs_rq we will |
| * post the final h_nr_running decrement below. |
| */ |
| if (cfs_rq_throttled(cfs_rq)) |
| break; |
| cfs_rq->h_nr_running--; |
| cfs_rq->idle_h_nr_running -= idle_h_nr_running; |
| |
| /* Don't dequeue parent if it has other entities besides us */ |
| if (cfs_rq->load.weight) { |
| /* Avoid re-evaluating load for this entity: */ |
| se = parent_entity(se); |
| /* |
| * Bias pick_next to pick a task from this cfs_rq, as |
| * p is sleeping when it is within its sched_slice. |
| */ |
| if (task_sleep && se && !throttled_hierarchy(cfs_rq)) |
| set_next_buddy(se); |
| break; |
| } |
| flags |= DEQUEUE_SLEEP; |
| } |
| |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| cfs_rq->h_nr_running--; |
| cfs_rq->idle_h_nr_running -= idle_h_nr_running; |
| |
| if (cfs_rq_throttled(cfs_rq)) |
| break; |
| |
| update_load_avg(cfs_rq, se, UPDATE_TG); |
| update_cfs_group(se); |
| } |
| |
| if (!se) |
| sub_nr_running(rq, 1); |
| |
| /* balance early to pull high priority tasks */ |
| if (unlikely(!was_sched_idle && sched_idle_rq(rq))) |
| rq->next_balance = jiffies; |
| |
| util_est_dequeue(&rq->cfs, p, task_sleep); |
| hrtick_update(rq); |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* Working cpumask for: load_balance, load_balance_newidle. */ |
| DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); |
| DEFINE_PER_CPU(cpumask_var_t, select_idle_mask); |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| |
| static struct { |
| cpumask_var_t idle_cpus_mask; |
| atomic_t nr_cpus; |
| int has_blocked; /* Idle CPUS has blocked load */ |
| unsigned long next_balance; /* in jiffy units */ |
| unsigned long next_blocked; /* Next update of blocked load in jiffies */ |
| } nohz ____cacheline_aligned; |
| |
| #endif /* CONFIG_NO_HZ_COMMON */ |
| |
| static unsigned long cpu_load(struct rq *rq) |
| { |
| return cfs_rq_load_avg(&rq->cfs); |
| } |
| |
| /* |
| * cpu_load_without - compute CPU load without any contributions from *p |
| * @cpu: the CPU which load is requested |
| * @p: the task which load should be discounted |
| * |
| * The load of a CPU is defined by the load of tasks currently enqueued on that |
| * CPU as well as tasks which are currently sleeping after an execution on that |
| * CPU. |
| * |
| * This method returns the load of the specified CPU by discounting the load of |
| * the specified task, whenever the task is currently contributing to the CPU |
| * load. |
| */ |
| static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p) |
| { |
| struct cfs_rq *cfs_rq; |
| unsigned int load; |
| |
| /* Task has no contribution or is new */ |
| if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) |
| return cpu_load(rq); |
| |
| cfs_rq = &rq->cfs; |
| load = READ_ONCE(cfs_rq->avg.load_avg); |
| |
| /* Discount task's util from CPU's util */ |
| lsub_positive(&load, task_h_load(p)); |
| |
| return load; |
| } |
| |
| static unsigned long capacity_of(int cpu) |
| { |
| return cpu_rq(cpu)->cpu_capacity; |
| } |
| |
| static void record_wakee(struct task_struct *p) |
| { |
| /* |
| * Only decay a single time; tasks that have less then 1 wakeup per |
| * jiffy will not have built up many flips. |
| */ |
| if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) { |
| current->wakee_flips >>= 1; |
| current->wakee_flip_decay_ts = jiffies; |
| } |
| |
| if (current->last_wakee != p) { |
| current->last_wakee = p; |
| current->wakee_flips++; |
| } |
| } |
| |
| /* |
| * Detect M:N waker/wakee relationships via a switching-frequency heuristic. |
| * |
| * A waker of many should wake a different task than the one last awakened |
| * at a frequency roughly N times higher than one of its wakees. |
| * |
| * In order to determine whether we should let the load spread vs consolidating |
| * to shared cache, we look for a minimum 'flip' frequency of llc_size in one |
| * partner, and a factor of lls_size higher frequency in the other. |
| * |
| * With both conditions met, we can be relatively sure that the relationship is |
| * non-monogamous, with partner count exceeding socket size. |
| * |
| * Waker/wakee being client/server, worker/dispatcher, interrupt source or |
| * whatever is irrelevant, spread criteria is apparent partner count exceeds |
| * socket size. |
| */ |
| static int wake_wide(struct task_struct *p) |
| { |
| unsigned int master = current->wakee_flips; |
| unsigned int slave = p->wakee_flips; |
| int factor = this_cpu_read(sd_llc_size); |
| |
| if (master < slave) |
| swap(master, slave); |
| if (slave < factor || master < slave * factor) |
| return 0; |
| return 1; |
| } |
| |
| /* |
| * The purpose of wake_affine() is to quickly determine on which CPU we can run |
| * soonest. For the purpose of speed we only consider the waking and previous |
| * CPU. |
| * |
| * wake_affine_idle() - only considers 'now', it check if the waking CPU is |
| * cache-affine and is (or will be) idle. |
| * |
| * wake_affine_weight() - considers the weight to reflect the average |
| * scheduling latency of the CPUs. This seems to work |
| * for the overloaded case. |
| */ |
| static int |
| wake_affine_idle(int this_cpu, int prev_cpu, int sync) |
| { |
| /* |
| * If this_cpu is idle, it implies the wakeup is from interrupt |
| * context. Only allow the move if cache is shared. Otherwise an |
| * interrupt intensive workload could force all tasks onto one |
| * node depending on the IO topology or IRQ affinity settings. |
| * |
| * If the prev_cpu is idle and cache affine then avoid a migration. |
| * There is no guarantee that the cache hot data from an interrupt |
| * is more important than cache hot data on the prev_cpu and from |
| * a cpufreq perspective, it's better to have higher utilisation |
| * on one CPU. |
| */ |
| if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu)) |
| return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu; |
| |
| if (sync && cpu_rq(this_cpu)->nr_running == 1) |
| return this_cpu; |
| |
| return nr_cpumask_bits; |
| } |
| |
| static int |
| wake_affine_weight(struct sched_domain *sd, struct task_struct *p, |
| int this_cpu, int prev_cpu, int sync) |
| { |
| s64 this_eff_load, prev_eff_load; |
| unsigned long task_load; |
| |
| this_eff_load = cpu_load(cpu_rq(this_cpu)); |
| |
| if (sync) { |
| unsigned long current_load = task_h_load(current); |
| |
| if (current_load > this_eff_load) |
| return this_cpu; |
| |
| this_eff_load -= current_load; |
| } |
| |
| task_load = task_h_load(p); |
| |
| this_eff_load += task_load; |
| if (sched_feat(WA_BIAS)) |
| this_eff_load *= 100; |
| this_eff_load *= capacity_of(prev_cpu); |
| |
| prev_eff_load = cpu_load(cpu_rq(prev_cpu)); |
| prev_eff_load -= task_load; |
| if (sched_feat(WA_BIAS)) |
| prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2; |
| prev_eff_load *= capacity_of(this_cpu); |
| |
| /* |
| * If sync, adjust the weight of prev_eff_load such that if |
| * prev_eff == this_eff that select_idle_sibling() will consider |
| * stacking the wakee on top of the waker if no other CPU is |
| * idle. |
| */ |
| if (sync) |
| prev_eff_load += 1; |
| |
| return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits; |
| } |
| |
| static int wake_affine(struct sched_domain *sd, struct task_struct *p, |
| int this_cpu, int prev_cpu, int sync) |
| { |
| int target = nr_cpumask_bits; |
| |
| if (sched_feat(WA_IDLE)) |
| target = wake_affine_idle(this_cpu, prev_cpu, sync); |
| |
| if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits) |
| target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync); |
| |
| schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts); |
| if (target == nr_cpumask_bits) |
| return prev_cpu; |
| |
| schedstat_inc(sd->ttwu_move_affine); |
| schedstat_inc(p->se.statistics.nr_wakeups_affine); |
| return target; |
| } |
| |
| static struct sched_group * |
| find_idlest_group(struct sched_domain *sd, struct task_struct *p, |
| int this_cpu, int sd_flag); |
| |
| /* |
| * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group. |
| */ |
| static int |
| find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) |
| { |
| unsigned long load, min_load = ULONG_MAX; |
| unsigned int min_exit_latency = UINT_MAX; |
| u64 latest_idle_timestamp = 0; |
| int least_loaded_cpu = this_cpu; |
| int shallowest_idle_cpu = -1; |
| int i; |
| |
| /* Check if we have any choice: */ |
| if (group->group_weight == 1) |
| return cpumask_first(sched_group_span(group)); |
| |
| /* Traverse only the allowed CPUs */ |
| for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) { |
| if (sched_idle_cpu(i)) |
| return i; |
| |
| if (available_idle_cpu(i)) { |
| struct rq *rq = cpu_rq(i); |
| struct cpuidle_state *idle = idle_get_state(rq); |
| if (idle && idle->exit_latency < min_exit_latency) { |
| /* |
| * We give priority to a CPU whose idle state |
| * has the smallest exit latency irrespective |
| * of any idle timestamp. |
| */ |
| min_exit_latency = idle->exit_latency; |
| latest_idle_timestamp = rq->idle_stamp; |
| shallowest_idle_cpu = i; |
| } else if ((!idle || idle->exit_latency == min_exit_latency) && |
| rq->idle_stamp > latest_idle_timestamp) { |
| /* |
| * If equal or no active idle state, then |
| * the most recently idled CPU might have |
| * a warmer cache. |
| */ |
| latest_idle_timestamp = rq->idle_stamp; |
| shallowest_idle_cpu = i; |
| } |
| } else if (shallowest_idle_cpu == -1) { |
| load = cpu_load(cpu_rq(i)); |
| if (load < min_load) { |
| min_load = load; |
| least_loaded_cpu = i; |
| } |
| } |
| } |
| |
| return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; |
| } |
| |
| static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p, |
| int cpu, int prev_cpu, int sd_flag) |
| { |
| int new_cpu = cpu; |
| |
| if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr)) |
| return prev_cpu; |
| |
| /* |
| * We need task's util for cpu_util_without, sync it up to |
| * prev_cpu's last_update_time. |
| */ |
| if (!(sd_flag & SD_BALANCE_FORK)) |
| sync_entity_load_avg(&p->se); |
| |
| while (sd) { |
| struct sched_group *group; |
| struct sched_domain *tmp; |
| int weight; |
| |
| if (!(sd->flags & sd_flag)) { |
| sd = sd->child; |
| continue; |
| } |
| |
| group = find_idlest_group(sd, p, cpu, sd_flag); |
| if (!group) { |
| sd = sd->child; |
| continue; |
| } |
| |
| new_cpu = find_idlest_group_cpu(group, p, cpu); |
| if (new_cpu == cpu) { |
| /* Now try balancing at a lower domain level of 'cpu': */ |
| sd = sd->child; |
| continue; |
| } |
| |
| /* Now try balancing at a lower domain level of 'new_cpu': */ |
| cpu = new_cpu; |
| weight = sd->span_weight; |
| sd = NULL; |
| for_each_domain(cpu, tmp) { |
| if (weight <= tmp->span_weight) |
| break; |
| if (tmp->flags & sd_flag) |
| sd = tmp; |
| } |
| } |
| |
| return new_cpu; |
| } |
| |
| #ifdef CONFIG_SCHED_SMT |
| DEFINE_STATIC_KEY_FALSE(sched_smt_present); |
| EXPORT_SYMBOL_GPL(sched_smt_present); |
| |
| static inline void set_idle_cores(int cpu, int val) |
| { |
| struct sched_domain_shared *sds; |
| |
| sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); |
| if (sds) |
| WRITE_ONCE(sds->has_idle_cores, val); |
| } |
| |
| static inline bool test_idle_cores(int cpu, bool def) |
| { |
| struct sched_domain_shared *sds; |
| |
| sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); |
| if (sds) |
| return READ_ONCE(sds->has_idle_cores); |
| |
| return def; |
| } |
| |
| /* |
| * Scans the local SMT mask to see if the entire core is idle, and records this |
| * information in sd_llc_shared->has_idle_cores. |
| * |
| * Since SMT siblings share all cache levels, inspecting this limited remote |
| * state should be fairly cheap. |
| */ |
| void __update_idle_core(struct rq *rq) |
| { |
| int core = cpu_of(rq); |
| int cpu; |
| |
| rcu_read_lock(); |
| if (test_idle_cores(core, true)) |
| goto unlock; |
| |
| for_each_cpu(cpu, cpu_smt_mask(core)) { |
| if (cpu == core) |
| continue; |
| |
| if (!available_idle_cpu(cpu)) |
| goto unlock; |
| } |
| |
| set_idle_cores(core, 1); |
| unlock: |
| rcu_read_unlock(); |
| } |
| |
| /* |
| * Scan the entire LLC domain for idle cores; this dynamically switches off if |
| * there are no idle cores left in the system; tracked through |
| * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above. |
| */ |
| static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) |
| { |
| struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); |
| int core, cpu; |
| |
| if (!static_branch_likely(&sched_smt_present)) |
| return -1; |
| |
| if (!test_idle_cores(target, false)) |
| return -1; |
| |
| cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); |
| |
| for_each_cpu_wrap(core, cpus, target) { |
| bool idle = true; |
| |
| for_each_cpu(cpu, cpu_smt_mask(core)) { |
| __cpumask_clear_cpu(cpu, cpus); |
| if (!available_idle_cpu(cpu)) |
| idle = false; |
| } |
| |
| if (idle) |
| return core; |
| } |
| |
| /* |
| * Failed to find an idle core; stop looking for one. |
| */ |
| set_idle_cores(target, 0); |
| |
| return -1; |
| } |
| |
| /* |
| * Scan the local SMT mask for idle CPUs. |
| */ |
| static int select_idle_smt(struct task_struct *p, int target) |
| { |
| int cpu; |
| |
| if (!static_branch_likely(&sched_smt_present)) |
| return -1; |
| |
| for_each_cpu(cpu, cpu_smt_mask(target)) { |
| if (!cpumask_test_cpu(cpu, p->cpus_ptr)) |
| continue; |
| if (available_idle_cpu(cpu) || sched_idle_cpu(cpu)) |
| return cpu; |
| } |
| |
| return -1; |
| } |
| |
| #else /* CONFIG_SCHED_SMT */ |
| |
| static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) |
| { |
| return -1; |
| } |
| |
| static inline int select_idle_smt(struct task_struct *p, int target) |
| { |
| return -1; |
| } |
| |
| #endif /* CONFIG_SCHED_SMT */ |
| |
| /* |
| * Scan the LLC domain for idle CPUs; this is dynamically regulated by |
| * comparing the average scan cost (tracked in sd->avg_scan_cost) against the |
| * average idle time for this rq (as found in rq->avg_idle). |
| */ |
| static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target) |
| { |
| struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); |
| struct sched_domain *this_sd; |
| u64 avg_cost, avg_idle; |
| u64 time, cost; |
| s64 delta; |
| int this = smp_processor_id(); |
| int cpu, nr = INT_MAX; |
| |
| this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); |
| if (!this_sd) |
| return -1; |
| |
| /* |
| * Due to large variance we need a large fuzz factor; hackbench in |
| * particularly is sensitive here. |
| */ |
| avg_idle = this_rq()->avg_idle / 512; |
| avg_cost = this_sd->avg_scan_cost + 1; |
| |
| if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) |
| return -1; |
| |
| if (sched_feat(SIS_PROP)) { |
| u64 span_avg = sd->span_weight * avg_idle; |
| if (span_avg > 4*avg_cost) |
| nr = div_u64(span_avg, avg_cost); |
| else |
| nr = 4; |
| } |
| |
| time = cpu_clock(this); |
| |
| cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); |
| |
| for_each_cpu_wrap(cpu, cpus, target) { |
| if (!--nr) |
| return -1; |
| if (available_idle_cpu(cpu) || sched_idle_cpu(cpu)) |
| break; |
| } |
| |
| time = cpu_clock(this) - time; |
| cost = this_sd->avg_scan_cost; |
| delta = (s64)(time - cost) / 8; |
| this_sd->avg_scan_cost += delta; |
| |
| return cpu; |
| } |
| |
| /* |
| * Try and locate an idle core/thread in the LLC cache domain. |
| */ |
| static int select_idle_sibling(struct task_struct *p, int prev, int target) |
| { |
| struct sched_domain *sd; |
| int i, recent_used_cpu; |
| |
| if (available_idle_cpu(target) || sched_idle_cpu(target)) |
| return target; |
| |
| /* |
| * If the previous CPU is cache affine and idle, don't be stupid: |
| */ |
| if (prev != target && cpus_share_cache(prev, target) && |
| (available_idle_cpu(prev) || sched_idle_cpu(prev))) |
| return prev; |
| |
| /* Check a recently used CPU as a potential idle candidate: */ |
| recent_used_cpu = p->recent_used_cpu; |
| if (recent_used_cpu != prev && |
| recent_used_cpu != target && |
| cpus_share_cache(recent_used_cpu, target) && |
| (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) && |
| cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr)) { |
| /* |
| * Replace recent_used_cpu with prev as it is a potential |
| * candidate for the next wake: |
| */ |
| p->recent_used_cpu = prev; |
| return recent_used_cpu; |
| } |
| |
| sd = rcu_dereference(per_cpu(sd_llc, target)); |
| if (!sd) |
| return target; |
| |
| i = select_idle_core(p, sd, target); |
| if ((unsigned)i < nr_cpumask_bits) |
| return i; |
| |
| i = select_idle_cpu(p, sd, target); |
| if ((unsigned)i < nr_cpumask_bits) |
| return i; |
| |
| i = select_idle_smt(p, target); |
| if ((unsigned)i < nr_cpumask_bits) |
| return i; |
| |
| return target; |
| } |
| |
| /** |
| * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks |
| * @cpu: the CPU to get the utilization of |
| * |
| * The unit of the return value must be the one of capacity so we can compare |
| * the utilization with the capacity of the CPU that is available for CFS task |
| * (ie cpu_capacity). |
| * |
| * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the |
| * recent utilization of currently non-runnable tasks on a CPU. It represents |
| * the amount of utilization of a CPU in the range [0..capacity_orig] where |
| * capacity_orig is the cpu_capacity available at the highest frequency |
| * (arch_scale_freq_capacity()). |
| * The utilization of a CPU converges towards a sum equal to or less than the |
| * current capacity (capacity_curr <= capacity_orig) of the CPU because it is |
| * the running time on this CPU scaled by capacity_curr. |
| * |
| * The estimated utilization of a CPU is defined to be the maximum between its |
| * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks |
| * currently RUNNABLE on that CPU. |
| * This allows to properly represent the expected utilization of a CPU which |
| * has just got a big task running since a long sleep period. At the same time |
| * however it preserves the benefits of the "blocked utilization" in |
| * describing the potential for other tasks waking up on the same CPU. |
| * |
| * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even |
| * higher than capacity_orig because of unfortunate rounding in |
| * cfs.avg.util_avg or just after migrating tasks and new task wakeups until |
| * the average stabilizes with the new running time. We need to check that the |
| * utilization stays within the range of [0..capacity_orig] and cap it if |
| * necessary. Without utilization capping, a group could be seen as overloaded |
| * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of |
| * available capacity. We allow utilization to overshoot capacity_curr (but not |
| * capacity_orig) as it useful for predicting the capacity required after task |
| * migrations (scheduler-driven DVFS). |
| * |
| * Return: the (estimated) utilization for the specified CPU |
| */ |
| static inline unsigned long cpu_util(int cpu) |
| { |
| struct cfs_rq *cfs_rq; |
| unsigned int util; |
| |
| cfs_rq = &cpu_rq(cpu)->cfs; |
| util = READ_ONCE(cfs_rq->avg.util_avg); |
| |
| if (sched_feat(UTIL_EST)) |
| util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued)); |
| |
| return min_t(unsigned long, util, capacity_orig_of(cpu)); |
| } |
| |
| /* |
| * cpu_util_without: compute cpu utilization without any contributions from *p |
| * @cpu: the CPU which utilization is requested |
| * @p: the task which utilization should be discounted |
| * |
| * The utilization of a CPU is defined by the utilization of tasks currently |
| * enqueued on that CPU as well as tasks which are currently sleeping after an |
| * execution on that CPU. |
| * |
| * This method returns the utilization of the specified CPU by discounting the |
| * utilization of the specified task, whenever the task is currently |
| * contributing to the CPU utilization. |
| */ |
| static unsigned long cpu_util_without(int cpu, struct task_struct *p) |
| { |
| struct cfs_rq *cfs_rq; |
| unsigned int util; |
| |
| /* Task has no contribution or is new */ |
| if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) |
| return cpu_util(cpu); |
| |
| cfs_rq = &cpu_rq(cpu)->cfs; |
| util = READ_ONCE(cfs_rq->avg.util_avg); |
| |
| /* Discount task's util from CPU's util */ |
| lsub_positive(&util, task_util(p)); |
| |
| /* |
| * Covered cases: |
| * |
| * a) if *p is the only task sleeping on this CPU, then: |
| * cpu_util (== task_util) > util_est (== 0) |
| * and thus we return: |
| * cpu_util_without = (cpu_util - task_util) = 0 |
| * |
| * b) if other tasks are SLEEPING on this CPU, which is now exiting |
| * IDLE, then: |
| * cpu_util >= task_util |
| * cpu_util > util_est (== 0) |
| * and thus we discount *p's blocked utilization to return: |
| * cpu_util_without = (cpu_util - task_util) >= 0 |
| * |
| * c) if other tasks are RUNNABLE on that CPU and |
| * util_est > cpu_util |
| * then we use util_est since it returns a more restrictive |
| * estimation of the spare capacity on that CPU, by just |
| * considering the expected utilization of tasks already |
| * runnable on that CPU. |
| * |
| * Cases a) and b) are covered by the above code, while case c) is |
| * covered by the following code when estimated utilization is |
| * enabled. |
| */ |
| if (sched_feat(UTIL_EST)) { |
| unsigned int estimated = |
| READ_ONCE(cfs_rq->avg.util_est.enqueued); |
| |
| /* |
| * Despite the following checks we still have a small window |
| * for a possible race, when an execl's select_task_rq_fair() |
| * races with LB's detach_task(): |
| * |
| * detach_task() |
| * p->on_rq = TASK_ON_RQ_MIGRATING; |
| * ---------------------------------- A |
| * deactivate_task() \ |
| * dequeue_task() + RaceTime |
| * util_est_dequeue() / |
| * ---------------------------------- B |
| * |
| * The additional check on "current == p" it's required to |
| * properly fix the execl regression and it helps in further |
| * reducing the chances for the above race. |
| */ |
| if (unlikely(task_on_rq_queued(p) || current == p)) |
| lsub_positive(&estimated, _task_util_est(p)); |
| |
| util = max(util, estimated); |
| } |
| |
| /* |
| * Utilization (estimated) can exceed the CPU capacity, thus let's |
| * clamp to the maximum CPU capacity to ensure consistency with |
| * the cpu_util call. |
| */ |
| return min_t(unsigned long, util, capacity_orig_of(cpu)); |
| } |
| |
| /* |
| * Disable WAKE_AFFINE in the case where task @p doesn't fit in the |
| * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu. |
| * |
| * In that case WAKE_AFFINE doesn't make sense and we'll let |
| * BALANCE_WAKE sort things out. |
| */ |
| static int wake_cap(struct task_struct *p, int cpu, int prev_cpu) |
| { |
| long min_cap, max_cap; |
| |
| if (!static_branch_unlikely(&sched_asym_cpucapacity)) |
| return 0; |
| |
| min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu)); |
| max_cap = cpu_rq(cpu)->rd->max_cpu_capacity; |
| |
| /* Minimum capacity is close to max, no need to abort wake_affine */ |
| if (max_cap - min_cap < max_cap >> 3) |
| return 0; |
| |
| /* Bring task utilization in sync with prev_cpu */ |
| sync_entity_load_avg(&p->se); |
| |
| return !task_fits_capacity(p, min_cap); |
| } |
| |
| /* |
| * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued) |
| * to @dst_cpu. |
| */ |
| static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu) |
| { |
| struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs; |
| unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg); |
| |
| /* |
| * If @p migrates from @cpu to another, remove its contribution. Or, |
| * if @p migrates from another CPU to @cpu, add its contribution. In |
| * the other cases, @cpu is not impacted by the migration, so the |
| * util_avg should already be correct. |
| */ |
| if (task_cpu(p) == cpu && dst_cpu != cpu) |
| sub_positive(&util, task_util(p)); |
| else if (task_cpu(p) != cpu && dst_cpu == cpu) |
| util += task_util(p); |
| |
| if (sched_feat(UTIL_EST)) { |
| util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued); |
| |
| /* |
| * During wake-up, the task isn't enqueued yet and doesn't |
| * appear in the cfs_rq->avg.util_est.enqueued of any rq, |
| * so just add it (if needed) to "simulate" what will be |
| * cpu_util() after the task has been enqueued. |
| */ |
| if (dst_cpu == cpu) |
| util_est += _task_util_est(p); |
| |
| util = max(util, util_est); |
| } |
| |
| return min(util, capacity_orig_of(cpu)); |
| } |
| |
| /* |
| * compute_energy(): Estimates the energy that @pd would consume if @p was |
| * migrated to @dst_cpu. compute_energy() predicts what will be the utilization |
| * landscape of @pd's CPUs after the task migration, and uses the Energy Model |
| * to compute what would be the energy if we decided to actually migrate that |
| * task. |
| */ |
| static long |
| compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) |
| { |
| struct cpumask *pd_mask = perf_domain_span(pd); |
| unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask)); |
| unsigned long max_util = 0, sum_util = 0; |
| int cpu; |
| |
| /* |
| * The capacity state of CPUs of the current rd can be driven by CPUs |
| * of another rd if they belong to the same pd. So, account for the |
| * utilization of these CPUs too by masking pd with cpu_online_mask |
| * instead of the rd span. |
| * |
| * If an entire pd is outside of the current rd, it will not appear in |
| * its pd list and will not be accounted by compute_energy(). |
| */ |
| for_each_cpu_and(cpu, pd_mask, cpu_online_mask) { |
| unsigned long cpu_util, util_cfs = cpu_util_next(cpu, p, dst_cpu); |
| struct task_struct *tsk = cpu == dst_cpu ? p : NULL; |
| |
| /* |
| * Busy time computation: utilization clamping is not |
| * required since the ratio (sum_util / cpu_capacity) |
| * is already enough to scale the EM reported power |
| * consumption at the (eventually clamped) cpu_capacity. |
| */ |
| sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap, |
| ENERGY_UTIL, NULL); |
| |
| /* |
| * Performance domain frequency: utilization clamping |
| * must be considered since it affects the selection |
| * of the performance domain frequency. |
| * NOTE: in case RT tasks are running, by default the |
| * FREQUENCY_UTIL's utilization can be max OPP. |
| */ |
| cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap, |
| FREQUENCY_UTIL, tsk); |
| max_util = max(max_util, cpu_util); |
| } |
| |
| return em_pd_energy(pd->em_pd, max_util, sum_util); |
| } |
| |
| /* |
| * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the |
| * waking task. find_energy_efficient_cpu() looks for the CPU with maximum |
| * spare capacity in each performance domain and uses it as a potential |
| * candidate to execute the task. Then, it uses the Energy Model to figure |
| * out which of the CPU candidates is the most energy-efficient. |
| * |
| * The rationale for this heuristic is as follows. In a performance domain, |
| * all the most energy efficient CPU candidates (according to the Energy |
| * Model) are those for which we'll request a low frequency. When there are |
| * several CPUs for which the frequency request will be the same, we don't |
| * have enough data to break the tie between them, because the Energy Model |
| * only includes active power costs. With this model, if we assume that |
| * frequency requests follow utilization (e.g. using schedutil), the CPU with |
| * the maximum spare capacity in a performance domain is guaranteed to be among |
| * the best candidates of the performance domain. |
| * |
| * In practice, it could be preferable from an energy standpoint to pack |
| * small tasks on a CPU in order to let other CPUs go in deeper idle states, |
| * but that could also hurt our chances to go cluster idle, and we have no |
| * ways to tell with the current Energy Model if this is actually a good |
| * idea or not. So, find_energy_efficient_cpu() basically favors |
| * cluster-packing, and spreading inside a cluster. That should at least be |
| * a good thing for latency, and this is consistent with the idea that most |
| * of the energy savings of EAS come from the asymmetry of the system, and |
| * not so much from breaking the tie between identical CPUs. That's also the |
| * reason why EAS is enabled in the topology code only for systems where |
| * SD_ASYM_CPUCAPACITY is set. |
| * |
| * NOTE: Forkees are not accepted in the energy-aware wake-up path because |
| * they don't have any useful utilization data yet and it's not possible to |
| * forecast their impact on energy consumption. Consequently, they will be |
| * placed by find_idlest_cpu() on the least loaded CPU, which might turn out |
| * to be energy-inefficient in some use-cases. The alternative would be to |
| * bias new tasks towards specific types of CPUs first, or to try to infer |
| * their util_avg from the parent task, but those heuristics could hurt |
| * other use-cases too. So, until someone finds a better way to solve this, |
| * let's keep things simple by re-using the existing slow path. |
| */ |
| static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) |
| { |
| unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX; |
| struct root_domain *rd = cpu_rq(smp_processor_id())->rd; |
| unsigned long cpu_cap, util, base_energy = 0; |
| int cpu, best_energy_cpu = prev_cpu; |
| struct sched_domain *sd; |
| struct perf_domain *pd; |
| |
| rcu_read_lock(); |
| pd = rcu_dereference(rd->pd); |
| if (!pd || READ_ONCE(rd->overutilized)) |
| goto fail; |
| |
| /* |
| * Energy-aware wake-up happens on the lowest sched_domain starting |
| * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu. |
| */ |
| sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity)); |
| while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) |
| sd = sd->parent; |
| if (!sd) |
| goto fail; |
| |
| sync_entity_load_avg(&p->se); |
| if (!task_util_est(p)) |
| goto unlock; |
| |
| for (; pd; pd = pd->next) { |
| unsigned long cur_delta, spare_cap, max_spare_cap = 0; |
| unsigned long base_energy_pd; |
| int max_spare_cap_cpu = -1; |
| |
| /* Compute the 'base' energy of the pd, without @p */ |
| base_energy_pd = compute_energy(p, -1, pd); |
| base_energy += base_energy_pd; |
| |
| for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) { |
| if (!cpumask_test_cpu(cpu, p->cpus_ptr)) |
| continue; |
| |
| util = cpu_util_next(cpu, p, cpu); |
| cpu_cap = capacity_of(cpu); |
| spare_cap = cpu_cap - util; |
| |
| /* |
| * Skip CPUs that cannot satisfy the capacity request. |
| * IOW, placing the task there would make the CPU |
| * overutilized. Take uclamp into account to see how |
| * much capacity we can get out of the CPU; this is |
| * aligned with schedutil_cpu_util(). |
| */ |
| util = uclamp_rq_util_with(cpu_rq(cpu), util, p); |
| if (!fits_capacity(util, cpu_cap)) |
| continue; |
| |
| /* Always use prev_cpu as a candidate. */ |
| if (cpu == prev_cpu) { |
| prev_delta = compute_energy(p, prev_cpu, pd); |
| prev_delta -= base_energy_pd; |
| best_delta = min(best_delta, prev_delta); |
| } |
| |
| /* |
| * Find the CPU with the maximum spare capacity in |
| * the performance domain |
| */ |
| if (spare_cap > max_spare_cap) { |
| max_spare_cap = spare_cap; |
| max_spare_cap_cpu = cpu; |
| } |
| } |
| |
| /* Evaluate the energy impact of using this CPU. */ |
| if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) { |
| cur_delta = compute_energy(p, max_spare_cap_cpu, pd); |
| cur_delta -= base_energy_pd; |
| if (cur_delta < best_delta) { |
| best_delta = cur_delta; |
| best_energy_cpu = max_spare_cap_cpu; |
| } |
| } |
| } |
| unlock: |
| rcu_read_unlock(); |
| |
| /* |
| * Pick the best CPU if prev_cpu cannot be used, or if it saves at |
| * least 6% of the energy used by prev_cpu. |
| */ |
| if (prev_delta == ULONG_MAX) |
| return best_energy_cpu; |
| |
| if ((prev_delta - best_delta) > ((prev_delta + base_energy) >> 4)) |
| return best_energy_cpu; |
| |
| return prev_cpu; |
| |
| fail: |
| rcu_read_unlock(); |
| |
| return -1; |
| } |
| |
| /* |
| * select_task_rq_fair: Select target runqueue for the waking task in domains |
| * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, |
| * SD_BALANCE_FORK, or SD_BALANCE_EXEC. |
| * |
| * Balances load by selecting the idlest CPU in the idlest group, or under |
| * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set. |
| * |
| * Returns the target CPU number. |
| * |
| * preempt must be disabled. |
| */ |
| static int |
| select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags) |
| { |
| struct sched_domain *tmp, *sd = NULL; |
| int cpu = smp_processor_id(); |
| int new_cpu = prev_cpu; |
| int want_affine = 0; |
| int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING); |
| |
| if (sd_flag & SD_BALANCE_WAKE) { |
| record_wakee(p); |
| |
| if (sched_energy_enabled()) { |
| new_cpu = find_energy_efficient_cpu(p, prev_cpu); |
| if (new_cpu >= 0) |
| return new_cpu; |
| new_cpu = prev_cpu; |
| } |
| |
| want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) && |
| cpumask_test_cpu(cpu, p->cpus_ptr); |
| } |
| |
| rcu_read_lock(); |
| for_each_domain(cpu, tmp) { |
| if (!(tmp->flags & SD_LOAD_BALANCE)) |
| break; |
| |
| /* |
| * If both 'cpu' and 'prev_cpu' are part of this domain, |
| * cpu is a valid SD_WAKE_AFFINE target. |
| */ |
| if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && |
| cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { |
| if (cpu != prev_cpu) |
| new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync); |
| |
| sd = NULL; /* Prefer wake_affine over balance flags */ |
| break; |
| } |
| |
| if (tmp->flags & sd_flag) |
| sd = tmp; |
| else if (!want_affine) |
| break; |
| } |
| |
| if (unlikely(sd)) { |
| /* Slow path */ |
| new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag); |
| } else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */ |
| /* Fast path */ |
| |
| new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); |
| |
| if (want_affine) |
| current->recent_used_cpu = cpu; |
| } |
| rcu_read_unlock(); |
| |
| return new_cpu; |
| } |
| |
| static void detach_entity_cfs_rq(struct sched_entity *se); |
| |
| /* |
| * Called immediately before a task is migrated to a new CPU; task_cpu(p) and |
| * cfs_rq_of(p) references at time of call are still valid and identify the |
| * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held. |
| */ |
| static void migrate_task_rq_fair(struct task_struct *p, int new_cpu) |
| { |
| /* |
| * As blocked tasks retain absolute vruntime the migration needs to |
| * deal with this by subtracting the old and adding the new |
| * min_vruntime -- the latter is done by enqueue_entity() when placing |
| * the task on the new runqueue. |
| */ |
| if (p->state == TASK_WAKING) { |
| struct sched_entity *se = &p->se; |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| u64 min_vruntime; |
| |
| #ifndef CONFIG_64BIT |
| u64 min_vruntime_copy; |
| |
| do { |
| min_vruntime_copy = cfs_rq->min_vruntime_copy; |
| smp_rmb(); |
| min_vruntime = cfs_rq->min_vruntime; |
| } while (min_vruntime != min_vruntime_copy); |
| #else |
| min_vruntime = cfs_rq->min_vruntime; |
| #endif |
| |
| se->vruntime -= min_vruntime; |
| } |
| |
| if (p->on_rq == TASK_ON_RQ_MIGRATING) { |
| /* |
| * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old' |
| * rq->lock and can modify state directly. |
| */ |
| lockdep_assert_held(&task_rq(p)->lock); |
| detach_entity_cfs_rq(&p->se); |
| |
| } else { |
| /* |
| * We are supposed to update the task to "current" time, then |
| * its up to date and ready to go to new CPU/cfs_rq. But we |
| * have difficulty in getting what current time is, so simply |
| * throw away the out-of-date time. This will result in the |
| * wakee task is less decayed, but giving the wakee more load |
| * sounds not bad. |
| */ |
| remove_entity_load_avg(&p->se); |
| } |
| |
| /* Tell new CPU we are migrated */ |
| p->se.avg.last_update_time = 0; |
| |
| /* We have migrated, no longer consider this task hot */ |
| p->se.exec_start = 0; |
| |
| update_scan_period(p, new_cpu); |
| } |
| |
| static void task_dead_fair(struct task_struct *p) |
| { |
| remove_entity_load_avg(&p->se); |
| } |
| |
| static int |
| balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
| { |
| if (rq->nr_running) |
| return 1; |
| |
| return newidle_balance(rq, rf) != 0; |
| } |
| #endif /* CONFIG_SMP */ |
| |
| static unsigned long wakeup_gran(struct sched_entity *se) |
| { |
| unsigned long gran = sysctl_sched_wakeup_granularity; |
| |
| /* |
| * Since its curr running now, convert the gran from real-time |
| * to virtual-time in his units. |
| * |
| * By using 'se' instead of 'curr' we penalize light tasks, so |
| * they get preempted easier. That is, if 'se' < 'curr' then |
| * the resulting gran will be larger, therefore penalizing the |
| * lighter, if otoh 'se' > 'curr' then the resulting gran will |
| * be smaller, again penalizing the lighter task. |
| * |
| * This is especially important for buddies when the leftmost |
| * task is higher priority than the buddy. |
| */ |
| return calc_delta_fair(gran, se); |
| } |
| |
| /* |
| * Should 'se' preempt 'curr'. |
| * |
| * |s1 |
| * |s2 |
| * |s3 |
| * g |
| * |<--->|c |
| * |
| * w(c, s1) = -1 |
| * w(c, s2) = 0 |
| * w(c, s3) = 1 |
| * |
| */ |
| static int |
| wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) |
| { |
| s64 gran, vdiff = curr->vruntime - se->vruntime; |
| |
| if (vdiff <= 0) |
| return -1; |
| |
| gran = wakeup_gran(se); |
| if (vdiff > gran) |
| return 1; |
| |
| return 0; |
| } |
| |
| static void set_last_buddy(struct sched_entity *se) |
| { |
| if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se)))) |
| return; |
| |
| for_each_sched_entity(se) { |
| if (SCHED_WARN_ON(!se->on_rq)) |
| return; |
| cfs_rq_of(se)->last = se; |
| } |
| } |
| |
| static void set_next_buddy(struct sched_entity *se) |
| { |
| if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se)))) |
| return; |
| |
| for_each_sched_entity(se) { |
| if (SCHED_WARN_ON(!se->on_rq)) |
| return; |
| cfs_rq_of(se)->next = se; |
| } |
| } |
| |
| static void set_skip_buddy(struct sched_entity *se) |
| { |
| for_each_sched_entity(se) |
| cfs_rq_of(se)->skip = se; |
| } |
| |
| /* |
| * Preempt the current task with a newly woken task if needed: |
| */ |
| static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) |
| { |
| struct task_struct *curr = rq->curr; |
| struct sched_entity *se = &curr->se, *pse = &p->se; |
| struct cfs_rq *cfs_rq = task_cfs_rq(curr); |
| int scale = cfs_rq->nr_running >= sched_nr_latency; |
| int next_buddy_marked = 0; |
| |
| if (unlikely(se == pse)) |
| return; |
| |
| /* |
| * This is possible from callers such as attach_tasks(), in which we |
| * unconditionally check_prempt_curr() after an enqueue (which may have |
| * lead to a throttle). This both saves work and prevents false |
| * next-buddy nomination below. |
| */ |
| if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) |
| return; |
| |
| if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { |
| set_next_buddy(pse); |
| next_buddy_marked = 1; |
| } |
| |
| /* |
| * We can come here with TIF_NEED_RESCHED already set from new task |
| * wake up path. |
| * |
| * Note: this also catches the edge-case of curr being in a throttled |
| * group (e.g. via set_curr_task), since update_curr() (in the |
| * enqueue of curr) will have resulted in resched being set. This |
| * prevents us from potentially nominating it as a false LAST_BUDDY |
| * below. |
| */ |
| if (test_tsk_need_resched(curr)) |
| return; |
| |
| /* Idle tasks are by definition preempted by non-idle tasks. */ |
| if (unlikely(task_has_idle_policy(curr)) && |
| likely(!task_has_idle_policy(p))) |
| goto preempt; |
| |
| /* |
| * Batch and idle tasks do not preempt non-idle tasks (their preemption |
| * is driven by the tick): |
| */ |
| if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) |
| return; |
| |
| find_matching_se(&se, &pse); |
| update_curr(cfs_rq_of(se)); |
| BUG_ON(!pse); |
| if (wakeup_preempt_entity(se, pse) == 1) { |
| /* |
| * Bias pick_next to pick the sched entity that is |
| * triggering this preemption. |
| */ |
| if (!next_buddy_marked) |
| set_next_buddy(pse); |
| goto preempt; |
| } |
| |
| return; |
| |
| preempt: |
| resched_curr(rq); |
| /* |
| * Only set the backward buddy when the current task is still |
| * on the rq. This can happen when a wakeup gets interleaved |
| * with schedule on the ->pre_schedule() or idle_balance() |
| * point, either of which can * drop the rq lock. |
| * |
| * Also, during early boot the idle thread is in the fair class, |
| * for obvious reasons its a bad idea to schedule back to it. |
| */ |
| if (unlikely(!se->on_rq || curr == rq->idle)) |
| return; |
| |
| if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) |
| set_last_buddy(se); |
| } |
| |
| struct task_struct * |
| pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
| { |
| struct cfs_rq *cfs_rq = &rq->cfs; |
| struct sched_entity *se; |
| struct task_struct *p; |
| int new_tasks; |
| |
| again: |
| if (!sched_fair_runnable(rq)) |
| goto idle; |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| if (!prev || prev->sched_class != &fair_sched_class) |
| goto simple; |
| |
| /* |
| * Because of the set_next_buddy() in dequeue_task_fair() it is rather |
| * likely that a next task is from the same cgroup as the current. |
| * |
| * Therefore attempt to avoid putting and setting the entire cgroup |
| * hierarchy, only change the part that actually changes. |
| */ |
| |
| do { |
| struct sched_entity *curr = cfs_rq->curr; |
| |
| /* |
| * Since we got here without doing put_prev_entity() we also |
| * have to consider cfs_rq->curr. If it is still a runnable |
| * entity, update_curr() will update its vruntime, otherwise |
| * forget we've ever seen it. |
| */ |
| if (curr) { |
| if (curr->on_rq) |
| update_curr(cfs_rq); |
| else |
| curr = NULL; |
| |
| /* |
| * This call to check_cfs_rq_runtime() will do the |
| * throttle and dequeue its entity in the parent(s). |
| * Therefore the nr_running test will indeed |
| * be correct. |
| */ |
| if (unlikely(check_cfs_rq_runtime(cfs_rq))) { |
| cfs_rq = &rq->cfs; |
| |
| if (!cfs_rq->nr_running) |
| goto idle; |
| |
| goto simple; |
| } |
| } |
| |
| se = pick_next_entity(cfs_rq, curr); |
| cfs_rq = group_cfs_rq(se); |
| } while (cfs_rq); |
| |
| p = task_of(se); |
| |
| /* |
| * Since we haven't yet done put_prev_entity and if the selected task |
| * is a different task than we started out with, try and touch the |
| * least amount of cfs_rqs. |
| */ |
| if (prev != p) { |
| struct sched_entity *pse = &prev->se; |
| |
| while (!(cfs_rq = is_same_group(se, pse))) { |
| int se_depth = se->depth; |
| int pse_depth = pse->depth; |
| |
| if (se_depth <= pse_depth) { |
| put_prev_entity(cfs_rq_of(pse), pse); |
| pse = parent_entity(pse); |
| } |
| if (se_depth >= pse_depth) { |
| set_next_entity(cfs_rq_of(se), se); |
| se = parent_entity(se); |
| } |
| } |
| |
| put_prev_entity(cfs_rq, pse); |
| set_next_entity(cfs_rq, se); |
| } |
| |
| goto done; |
| simple: |
| #endif |
| if (prev) |
| put_prev_task(rq, prev); |
| |
| do { |
| se = pick_next_entity(cfs_rq, NULL); |
| set_next_entity(cfs_rq, se); |
| cfs_rq = group_cfs_rq(se); |
| } while (cfs_rq); |
| |
| p = task_of(se); |
| |
| done: __maybe_unused; |
| #ifdef CONFIG_SMP |
| /* |
| * Move the next running task to the front of |
| * the list, so our cfs_tasks list becomes MRU |
| * one. |
| */ |
| list_move(&p->se.group_node, &rq->cfs_tasks); |
| #endif |
| |
| if (hrtick_enabled(rq)) |
| hrtick_start_fair(rq, p); |
| |
| update_misfit_status(p, rq); |
| |
| return p; |
| |
| idle: |
| if (!rf) |
| return NULL; |
| |
| new_tasks = newidle_balance(rq, rf); |
| |
| /* |
| * Because newidle_balance() releases (and re-acquires) rq->lock, it is |
| * possible for any higher priority task to appear. In that case we |
| * must re-start the pick_next_entity() loop. |
| */ |
| if (new_tasks < 0) |
| return RETRY_TASK; |
| |
| if (new_tasks > 0) |
| goto again; |
| |
| /* |
| * rq is about to be idle, check if we need to update the |
| * lost_idle_time of clock_pelt |
| */ |
| update_idle_rq_clock_pelt(rq); |
| |
| return NULL; |
| } |
| |
| static struct task_struct *__pick_next_task_fair(struct rq *rq) |
| { |
| return pick_next_task_fair(rq, NULL, NULL); |
| } |
| |
| /* |
| * Account for a descheduled task: |
| */ |
| static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) |
| { |
| struct sched_entity *se = &prev->se; |
| struct cfs_rq *cfs_rq; |
| |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| put_prev_entity(cfs_rq, se); |
| } |
| } |
| |
| /* |
| * sched_yield() is very simple |
| * |
| * The magic of dealing with the ->skip buddy is in pick_next_entity. |
| */ |
| static void yield_task_fair(struct rq *rq) |
| { |
| struct task_struct *curr = rq->curr; |
| struct cfs_rq *cfs_rq = task_cfs_rq(curr); |
| struct sched_entity *se = &curr->se; |
| |
| /* |
| * Are we the only task in the tree? |
| */ |
| if (unlikely(rq->nr_running == 1)) |
| return; |
| |
| clear_buddies(cfs_rq, se); |
| |
| if (curr->policy != SCHED_BATCH) { |
| update_rq_clock(rq); |
| /* |
| * Update run-time statistics of the 'current'. |
| */ |
| update_curr(cfs_rq); |
| /* |
| * Tell update_rq_clock() that we've just updated, |
| * so we don't do microscopic update in schedule() |
| * and double the fastpath cost. |
| */ |
| rq_clock_skip_update(rq); |
| } |
| |
| set_skip_buddy(se); |
| } |
| |
| static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) |
| { |
| struct sched_entity *se = &p->se; |
| |
| /* throttled hierarchies are not runnable */ |
| if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) |
| return false; |
| |
| /* Tell the scheduler that we'd really like pse to run next. */ |
| set_next_buddy(se); |
| |
| yield_task_fair(rq); |
| |
| return true; |
| } |
| |
| #ifdef CONFIG_SMP |
| /************************************************** |
| * Fair scheduling class load-balancing methods. |
| * |
| * BASICS |
| * |
| * The purpose of load-balancing is to achieve the same basic fairness the |
| * per-CPU scheduler provides, namely provide a proportional amount of compute |
| * time to each task. This is expressed in the following equation: |
| * |
| * W_i,n/P_i == W_j,n/P_j for all i,j (1) |
| * |
| * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight |
| * W_i,0 is defined as: |
| * |
| * W_i,0 = \Sum_j w_i,j (2) |
| * |
| * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight |
| * is derived from the nice value as per sched_prio_to_weight[]. |
| * |
| * The weight average is an exponential decay average of the instantaneous |
| * weight: |
| * |
| * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3) |
| * |
| * C_i is the compute capacity of CPU i, typically it is the |
| * fraction of 'recent' time available for SCHED_OTHER task execution. But it |
| * can also include other factors [XXX]. |
| * |
| * To achieve this balance we define a measure of imbalance which follows |
| * directly from (1): |
| * |
| * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4) |
| * |
| * We them move tasks around to minimize the imbalance. In the continuous |
| * function space it is obvious this converges, in the discrete case we get |
| * a few fun cases generally called infeasible weight scenarios. |
| * |
| * [XXX expand on: |
| * - infeasible weights; |
| * - local vs global optima in the discrete case. ] |
| * |
| * |
| * SCHED DOMAINS |
| * |
| * In order to solve the imbalance equation (4), and avoid the obvious O(n^2) |
| * for all i,j solution, we create a tree of CPUs that follows the hardware |
| * topology where each level pairs two lower groups (or better). This results |
| * in O(log n) layers. Furthermore we reduce the number of CPUs going up the |
| * tree to only the first of the previous level and we decrease the frequency |
| * of load-balance at each level inv. proportional to the number of CPUs in |
| * the groups. |
| * |
| * This yields: |
| * |
| * log_2 n 1 n |
| * \Sum { --- * --- * 2^i } = O(n) (5) |
| * i = 0 2^i 2^i |
| * `- size of each group |
| * | | `- number of CPUs doing load-balance |
| * | `- freq |
| * `- sum over all levels |
| * |
| * Coupled with a limit on how many tasks we can migrate every balance pass, |
| * this makes (5) the runtime complexity of the balancer. |
| * |
| * An important property here is that each CPU is still (indirectly) connected |
| * to every other CPU in at most O(log n) steps: |
| * |
| * The adjacency matrix of the resulting graph is given by: |
| * |
| * log_2 n |
| * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6) |
| * k = 0 |
| * |
| * And you'll find that: |
| * |
| * A^(log_2 n)_i,j != 0 for all i,j (7) |
| * |
| * Showing there's indeed a path between every CPU in at most O(log n) steps. |
| * The task movement gives a factor of O(m), giving a convergence complexity |
| * of: |
| * |
| * O(nm log n), n := nr_cpus, m := nr_tasks (8) |
| * |
| * |
| * WORK CONSERVING |
| * |
| * In order to avoid CPUs going idle while there's still work to do, new idle |
| * balancing is more aggressive and has the newly idle CPU iterate up the domain |
| * tree itself instead of relying on other CPUs to bring it work. |
| * |
| * This adds some complexity to both (5) and (8) but it reduces the total idle |
| * time. |
| * |
| * [XXX more?] |
| * |
| * |
| * CGROUPS |
| * |
| * Cgroups make a horror show out of (2), instead of a simple sum we get: |
| * |
| * s_k,i |
| * W_i,0 = \Sum_j \Prod_k w_k * ----- (9) |
| * S_k |
| * |
| * Where |
| * |
| * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10) |
| * |
| * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i. |
| * |
| * The big problem is S_k, its a global sum needed to compute a local (W_i) |
| * property. |
| * |
| * [XXX write more on how we solve this.. _after_ merging pjt's patches that |
| * rewrite all of this once again.] |
| */ |
| |
| static unsigned long __read_mostly max_load_balance_interval = HZ/10; |
| |
| enum fbq_type { regular, remote, all }; |
| |
| /* |
| * 'group_type' describes the group of CPUs at the moment of load balancing. |
| * |
| * The enum is ordered by pulling priority, with the group with lowest priority |
| * first so the group_type can simply be compared when selecting the busiest |
| * group. See update_sd_pick_busiest(). |
| */ |
| enum group_type { |
| /* The group has spare capacity that can be used to run more tasks. */ |
| group_has_spare = 0, |
| /* |
| * The group is fully used and the tasks don't compete for more CPU |
| * cycles. Nevertheless, some tasks might wait before running. |
| */ |
| group_fully_busy, |
| /* |
| * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity |
| * and must be migrated to a more powerful CPU. |
| */ |
| group_misfit_task, |
| /* |
| * SD_ASYM_PACKING only: One local CPU with higher capacity is available, |
| * and the task should be migrated to it instead of running on the |
| * current CPU. |
| */ |
| group_asym_packing, |
| /* |
| * The tasks' affinity constraints previously prevented the scheduler |
| * from balancing the load across the system. |
| */ |
| group_imbalanced, |
| /* |
| * The CPU is overloaded and can't provide expected CPU cycles to all |
| * tasks. |
| */ |
| group_overloaded |
| }; |
| |
| enum migration_type { |
| migrate_load = 0, |
| migrate_util, |
| migrate_task, |
| migrate_misfit |
| }; |
| |
| #define LBF_ALL_PINNED 0x01 |
| #define LBF_NEED_BREAK 0x02 |
| #define LBF_DST_PINNED 0x04 |
| #define LBF_SOME_PINNED 0x08 |
| #define LBF_NOHZ_STATS 0x10 |
| #define LBF_NOHZ_AGAIN 0x20 |
| |
| struct lb_env { |
| struct sched_domain *sd; |
| |
| struct rq *src_rq; |
| int src_cpu; |
| |
| int dst_cpu; |
| struct rq *dst_rq; |
| |
| struct cpumask *dst_grpmask; |
| int new_dst_cpu; |
| enum cpu_idle_type idle; |
| long imbalance; |
| /* The set of CPUs under consideration for load-balancing */ |
| struct cpumask *cpus; |
| |
| unsigned int flags; |
| |
| unsigned int loop; |
| unsigned int loop_break; |
| unsigned int loop_max; |
| |
| enum fbq_type fbq_type; |
| enum migration_type migration_type; |
| struct list_head tasks; |
| }; |
| |
| /* |
| * Is this task likely cache-hot: |
| */ |
| static int task_hot(struct task_struct *p, struct lb_env *env) |
| { |
| s64 delta; |
| |
| lockdep_assert_held(&env->src_rq->lock); |
| |
| if (p->sched_class != &fair_sched_class) |
| return 0; |
| |
| if (unlikely(task_has_idle_policy(p))) |
| return 0; |
| |
| /* |
| * Buddy candidates are cache hot: |
| */ |
| if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running && |
| (&p->se == cfs_rq_of(&p->se)->next || |
| &p->se == cfs_rq_of(&p->se)->last)) |
| return 1; |
| |
| if (sysctl_sched_migration_cost == -1) |
| return 1; |
| if (sysctl_sched_migration_cost == 0) |
| return 0; |
| |
| delta = rq_clock_task(env->src_rq) - p->se.exec_start; |
| |
| return delta < (s64)sysctl_sched_migration_cost; |
| } |
| |
| #ifdef CONFIG_NUMA_BALANCING |
| /* |
| * Returns 1, if task migration degrades locality |
| * Returns 0, if task migration improves locality i.e migration preferred. |
| * Returns -1, if task migration is not affected by locality. |
| */ |
| static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env) |
| { |
| struct numa_group *numa_group = rcu_dereference(p->numa_group); |
| unsigned long src_weight, dst_weight; |
| int src_nid, dst_nid, dist; |
| |
| if (!static_branch_likely(&sched_numa_balancing)) |
| return -1; |
| |
| if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) |
| return -1; |
| |
| src_nid = cpu_to_node(env->src_cpu); |
| dst_nid = cpu_to_node(env->dst_cpu); |
| |
| if (src_nid == dst_nid) |
| return -1; |
| |
| /* Migrating away from the preferred node is always bad. */ |
| if (src_nid == p->numa_preferred_nid) { |
| if (env->src_rq->nr_running > env->src_rq->nr_preferred_running) |
| return 1; |
| else |
| return -1; |
| } |
| |
| /* Encourage migration to the preferred node. */ |
| if (dst_nid == p->numa_preferred_nid) |
| return 0; |
| |
| /* Leaving a core idle is often worse than degrading locality. */ |
| if (env->idle == CPU_IDLE) |
| return -1; |
| |
| dist = node_distance(src_nid, dst_nid); |
| if (numa_group) { |
| src_weight = group_weight(p, src_nid, dist); |
| dst_weight = group_weight(p, dst_nid, dist); |
| } else { |
| src_weight = task_weight(p, src_nid, dist); |
| dst_weight = task_weight(p, dst_nid, dist); |
| } |
| |
| return dst_weight < src_weight; |
| } |
| |
| #else |
| static inline int migrate_degrades_locality(struct task_struct *p, |
| struct lb_env *env) |
| { |
| return -1; |
| } |
| #endif |
| |
| /* |
| * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? |
| */ |
| static |
| int can_migrate_task(struct task_struct *p, struct lb_env *env) |
| { |
| int tsk_cache_hot; |
| |
| lockdep_assert_held(&env->src_rq->lock); |
| |
| /* |
| * We do not migrate tasks that are: |
| * 1) throttled_lb_pair, or |
| * 2) cannot be migrated to this CPU due to cpus_ptr, or |
| * 3) running (obviously), or |
| * 4) are cache-hot on their current CPU. |
| */ |
| if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) |
| return 0; |
| |
| if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) { |
| int cpu; |
| |
| schedstat_inc(p->se.statistics.nr_failed_migrations_affine); |
| |
| env->flags |= LBF_SOME_PINNED; |
| |
| /* |
| * Remember if this task can be migrated to any other CPU in |
| * our sched_group. We may want to revisit it if we couldn't |
| * meet load balance goals by pulling other tasks on src_cpu. |
| * |
| * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have |
| * already computed one in current iteration. |
| */ |
| if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED)) |
| return 0; |
| |
| /* Prevent to re-select dst_cpu via env's CPUs: */ |
| for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) { |
| if (cpumask_test_cpu(cpu, p->cpus_ptr)) { |
| env->flags |= LBF_DST_PINNED; |
| env->new_dst_cpu = cpu; |
| break; |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* Record that we found atleast one task that could run on dst_cpu */ |
| env->flags &= ~LBF_ALL_PINNED; |
| |
| if (task_running(env->src_rq, p)) { |
| schedstat_inc(p->se.statistics.nr_failed_migrations_running); |
| return 0; |
| } |
| |
| /* |
| * Aggressive migration if: |
| * 1) destination numa is preferred |
| * 2) task is cache cold, or |
| * 3) too many balance attempts have failed. |
| */ |
| tsk_cache_hot = migrate_degrades_locality(p, env); |
| if (tsk_cache_hot == -1) |
| tsk_cache_hot = task_hot(p, env); |
| |
| if (tsk_cache_hot <= 0 || |
| env->sd->nr_balance_failed > env->sd->cache_nice_tries) { |
| if (tsk_cache_hot == 1) { |
| schedstat_inc(env->sd->lb_hot_gained[env->idle]); |
| schedstat_inc(p->se.statistics.nr_forced_migrations); |
| } |
| return 1; |
| } |
| |
| schedstat_inc(p->se.statistics.nr_failed_migrations_hot); |
| return 0; |
| } |
| |
| /* |
| * detach_task() -- detach the task for the migration specified in env |
| */ |
| static void detach_task(struct task_struct *p, struct lb_env *env) |
| { |
| lockdep_assert_held(&env->src_rq->lock); |
| |
| deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK); |
| set_task_cpu(p, env->dst_cpu); |
| } |
| |
| /* |
| * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as |
| * part of active balancing operations within "domain". |
| * |
| * Returns a task if successful and NULL otherwise. |
| */ |
| static struct task_struct *detach_one_task(struct lb_env *env) |
| { |
| struct task_struct *p; |
| |
| lockdep_assert_held(&env->src_rq->lock); |
| |
| list_for_each_entry_reverse(p, |
| &env->src_rq->cfs_tasks, se.group_node) { |
| if (!can_migrate_task(p, env)) |
| continue; |
| |
| detach_task(p, env); |
| |
| /* |
| * Right now, this is only the second place where |
| * lb_gained[env->idle] is updated (other is detach_tasks) |
| * so we can safely collect stats here rather than |
| * inside detach_tasks(). |
| */ |
| schedstat_inc(env->sd->lb_gained[env->idle]); |
| return p; |
| } |
| return NULL; |
| } |
| |
| static const unsigned int sched_nr_migrate_break = 32; |
| |
| /* |
| * detach_tasks() -- tries to detach up to imbalance load/util/tasks from |
| * busiest_rq, as part of a balancing operation within domain "sd". |
| * |
| * Returns number of detached tasks if successful and 0 otherwise. |
| */ |
| static int detach_tasks(struct lb_env *env) |
| { |
| struct list_head *tasks = &env->src_rq->cfs_tasks; |
| unsigned long util, load; |
| struct task_struct *p; |
| int detached = 0; |
| |
| lockdep_assert_held(&env->src_rq->lock); |
| |
| if (env->imbalance <= 0) |
| return 0; |
| |
| while (!list_empty(tasks)) { |
| /* |
| * We don't want to steal all, otherwise we may be treated likewise, |
| * which could at worst lead to a livelock crash. |
| */ |
| if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) |
| break; |
| |
| p = list_last_entry(tasks, struct task_struct, se.group_node); |
| |
| env->loop++; |
| /* We've more or less seen every task there is, call it quits */ |
| if (env->loop > env->loop_max) |
| break; |
| |
| /* take a breather every nr_migrate tasks */ |
| if (env->loop > env->loop_break) { |
| env->loop_break += sched_nr_migrate_break; |
| env->flags |= LBF_NEED_BREAK; |
| break; |
| } |
| |
| if (!can_migrate_task(p, env)) |
| goto next; |
| |
| switch (env->migration_type) { |
| case migrate_load: |
| load = task_h_load(p); |
| |
| if (sched_feat(LB_MIN) && |
| load < 16 && !env->sd->nr_balance_failed) |
| goto next; |
| |
| /* |
| * Make sure that we don't migrate too much load. |
| * Nevertheless, let relax the constraint if |
| * scheduler fails to find a good waiting task to |
| * migrate. |
| */ |
| if (load/2 > env->imbalance && |
| env->sd->nr_balance_failed <= env->sd->cache_nice_tries) |
| goto next; |
| |
| env->imbalance -= load; |
| break; |
| |
| case migrate_util: |
| util = task_util_est(p); |
| |
| if (util > env->imbalance) |
| goto next; |
| |
| env->imbalance -= util; |
| break; |
| |
| case migrate_task: |
| env->imbalance--; |
| break; |
| |
| case migrate_misfit: |
| /* This is not a misfit task */ |
| if (task_fits_capacity(p, capacity_of(env->src_cpu))) |
| goto next; |
| |
| env->imbalance = 0; |
| break; |
| } |
| |
| detach_task(p, env); |
| list_add(&p->se.group_node, &env->tasks); |
| |
| detached++; |
| |
| #ifdef CONFIG_PREEMPTION |
| /* |
| * NEWIDLE balancing is a source of latency, so preemptible |
| * kernels will stop after the first task is detached to minimize |
| * the critical section. |
| */ |
| if (env->idle == CPU_NEWLY_IDLE) |
| break; |
| #endif |
| |
| /* |
| * We only want to steal up to the prescribed amount of |
| * load/util/tasks. |
| */ |
| if (env->imbalance <= 0) |
| break; |
| |
| continue; |
| next: |
| list_move(&p->se.group_node, tasks); |
| } |
| |
| /* |
| * Right now, this is one of only two places we collect this stat |
| * so we can safely collect detach_one_task() stats here rather |
| * than inside detach_one_task(). |
| */ |
| schedstat_add(env->sd->lb_gained[env->idle], detached); |
| |
| return detached; |
| } |
| |
| /* |
| * attach_task() -- attach the task detached by detach_task() to its new rq. |
| */ |
| static void attach_task(struct rq *rq, struct task_struct *p) |
| { |
| lockdep_assert_held(&rq->lock); |
| |
| BUG_ON(task_rq(p) != rq); |
| activate_task(rq, p, ENQUEUE_NOCLOCK); |
| check_preempt_curr(rq, p, 0); |
| } |
| |
| /* |
| * attach_one_task() -- attaches the task returned from detach_one_task() to |
| * its new rq. |
| */ |
| static void attach_one_task(struct rq *rq, struct task_struct *p) |
| { |
| struct rq_flags rf; |
| |
| rq_lock(rq, &rf); |
| update_rq_clock(rq); |
| attach_task(rq, p); |
| rq_unlock(rq, &rf); |
| } |
| |
| /* |
| * attach_tasks() -- attaches all tasks detached by detach_tasks() to their |
| * new rq. |
| */ |
| static void attach_tasks(struct lb_env *env) |
| { |
| struct list_head *tasks = &env->tasks; |
| struct task_struct *p; |
| struct rq_flags rf; |
| |
| rq_lock(env->dst_rq, &rf); |
| update_rq_clock(env->dst_rq); |
| |
| while (!list_empty(tasks)) { |
| p = list_first_entry(tasks, struct task_struct, se.group_node); |
| list_del_init(&p->se.group_node); |
| |
| attach_task(env->dst_rq, p); |
| } |
| |
| rq_unlock(env->dst_rq, &rf); |
| } |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) |
| { |
| if (cfs_rq->avg.load_avg) |
| return true; |
| |
| if (cfs_rq->avg.util_avg) |
| return true; |
| |
| return false; |
| } |
| |
| static inline bool others_have_blocked(struct rq *rq) |
| { |
| if (READ_ONCE(rq->avg_rt.util_avg)) |
| return true; |
| |
| if (READ_ONCE(rq->avg_dl.util_avg)) |
| return true; |
| |
| #ifdef CONFIG_HAVE_SCHED_AVG_IRQ |
| if (READ_ONCE(rq->avg_irq.util_avg)) |
| return true; |
| #endif |
| |
| return false; |
| } |
| |
| static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) |
| { |
| rq->last_blocked_load_update_tick = jiffies; |
| |
| if (!has_blocked) |
| rq->has_blocked_load = 0; |
| } |
| #else |
| static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; } |
| static inline bool others_have_blocked(struct rq *rq) { return false; } |
| static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {} |
| #endif |
| |
| static bool __update_blocked_others(struct rq *rq, bool *done) |
| { |
| const struct sched_class *curr_class; |
| u64 now = rq_clock_pelt(rq); |
| bool decayed; |
| |
| /* |
| * update_load_avg() can call cpufreq_update_util(). Make sure that RT, |
| * DL and IRQ signals have been updated before updating CFS. |
| */ |
| curr_class = rq->curr->sched_class; |
| |
| decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) | |
| update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) | |
| update_irq_load_avg(rq, 0); |
| |
| if (others_have_blocked(rq)) |
| *done = false; |
| |
| return decayed; |
| } |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| |
| static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) |
| { |
| if (cfs_rq->load.weight) |
| return false; |
| |
| if (cfs_rq->avg.load_sum) |
| return false; |
| |
| if (cfs_rq->avg.util_sum) |
| return false; |
| |
| if (cfs_rq->avg.runnable_load_sum) |
| return false; |
| |
| return true; |
| } |
| |
| static bool __update_blocked_fair(struct rq *rq, bool *done) |
| { |
| struct cfs_rq *cfs_rq, *pos; |
| bool decayed = false; |
| int cpu = cpu_of(rq); |
| |
| /* |
| * Iterates the task_group tree in a bottom up fashion, see |
| * list_add_leaf_cfs_rq() for details. |
| */ |
| for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) { |
| struct sched_entity *se; |
| |
| if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) { |
| update_tg_load_avg(cfs_rq, 0); |
| |
| if (cfs_rq == &rq->cfs) |
| decayed = true; |
| } |
| |
| /* Propagate pending load changes to the parent, if any: */ |
| se = cfs_rq->tg->se[cpu]; |
| if (se && !skip_blocked_update(se)) |
| update_load_avg(cfs_rq_of(se), se, 0); |
| |
| /* |
| * There can be a lot of idle CPU cgroups. Don't let fully |
| * decayed cfs_rqs linger on the list. |
| */ |
| if (cfs_rq_is_decayed(cfs_rq)) |
| list_del_leaf_cfs_rq(cfs_rq); |
| |
| /* Don't need periodic decay once load/util_avg are null */ |
| if (cfs_rq_has_blocked(cfs_rq)) |
| *done = false; |
| } |
| |
| return decayed; |
| } |
| |
| /* |
| * Compute the hierarchical load factor for cfs_rq and all its ascendants. |
| * This needs to be done in a top-down fashion because the load of a child |
| * group is a fraction of its parents load. |
| */ |
| static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) |
| { |
| struct rq *rq = rq_of(cfs_rq); |
| struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; |
| unsigned long now = jiffies; |
| unsigned long load; |
| |
| if (cfs_rq->last_h_load_update == now) |
| return; |
| |
| WRITE_ONCE(cfs_rq->h_load_next, NULL); |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| WRITE_ONCE(cfs_rq->h_load_next, se); |
| if (cfs_rq->last_h_load_update == now) |
| break; |
| } |
| |
| if (!se) { |
| cfs_rq->h_load = cfs_rq_load_avg(cfs_rq); |
| cfs_rq->last_h_load_update = now; |
| } |
| |
| while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) { |
| load = cfs_rq->h_load; |
| load = div64_ul(load * se->avg.load_avg, |
| cfs_rq_load_avg(cfs_rq) + 1); |
| cfs_rq = group_cfs_rq(se); |
| cfs_rq->h_load = load; |
| cfs_rq->last_h_load_update = now; |
| } |
| } |
| |
| static unsigned long task_h_load(struct task_struct *p) |
| { |
| struct cfs_rq *cfs_rq = task_cfs_rq(p); |
| |
| update_cfs_rq_h_load(cfs_rq); |
| return div64_ul(p->se.avg.load_avg * cfs_rq->h_load, |
| cfs_rq_load_avg(cfs_rq) + 1); |
| } |
| #else |
| static bool __update_blocked_fair(struct rq *rq, bool *done) |
| { |
| struct cfs_rq *cfs_rq = &rq->cfs; |
| bool decayed; |
| |
| decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq); |
| if (cfs_rq_has_blocked(cfs_rq)) |
| *done = false; |
| |
| return decayed; |
| } |
| |
| static unsigned long task_h_load(struct task_struct *p) |
| { |
| return p->se.avg.load_avg; |
| } |
| #endif |
| |
| static void update_blocked_averages(int cpu) |
| { |
| bool decayed = false, done = true; |
| struct rq *rq = cpu_rq(cpu); |
| struct rq_flags rf; |
| |
| rq_lock_irqsave(rq, &rf); |
| update_rq_clock(rq); |
| |
| decayed |= __update_blocked_others(rq, &done); |
| decayed |= __update_blocked_fair(rq, &done); |
| |
| update_blocked_load_status(rq, !done); |
| if (decayed) |
| cpufreq_update_util(rq, 0); |
| rq_unlock_irqrestore(rq, &rf); |
| } |
| |
| /********** Helpers for find_busiest_group ************************/ |
| |
| /* |
| * sg_lb_stats - stats of a sched_group required for load_balancing |
| */ |
| struct sg_lb_stats { |
| unsigned long avg_load; /*Avg load across the CPUs of the group */ |
| unsigned long group_load; /* Total load over the CPUs of the group */ |
| unsigned long group_capacity; |
| unsigned long group_util; /* Total utilization of the group */ |
| unsigned int sum_nr_running; /* Nr of tasks running in the group */ |
| unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */ |
| unsigned int idle_cpus; |
| unsigned int group_weight; |
| enum group_type group_type; |
| unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */ |
| unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */ |
| #ifdef CONFIG_NUMA_BALANCING |
| unsigned int nr_numa_running; |
| unsigned int nr_preferred_running; |
| #endif |
| }; |
| |
| /* |
| * sd_lb_stats - Structure to store the statistics of a sched_domain |
| * during load balancing. |
| */ |
| struct sd_lb_stats { |
| struct sched_group *busiest; /* Busiest group in this sd */ |
| struct sched_group *local; /* Local group in this sd */ |
| unsigned long total_load; /* Total load of all groups in sd */ |
| unsigned long total_capacity; /* Total capacity of all groups in sd */ |
| unsigned long avg_load; /* Average load across all groups in sd */ |
| unsigned int prefer_sibling; /* tasks should go to sibling first */ |
| |
| struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ |
| struct sg_lb_stats local_stat; /* Statistics of the local group */ |
| }; |
| |
| static inline void init_sd_lb_stats(struct sd_lb_stats *sds) |
| { |
| /* |
| * Skimp on the clearing to avoid duplicate work. We can avoid clearing |
| * local_stat because update_sg_lb_stats() does a full clear/assignment. |
| * We must however set busiest_stat::group_type and |
| * busiest_stat::idle_cpus to the worst busiest group because |
| * update_sd_pick_busiest() reads these before assignment. |
| */ |
| *sds = (struct sd_lb_stats){ |
| .busiest = NULL, |
| .local = NULL, |
| .total_load = 0UL, |
| .total_capacity = 0UL, |
| .busiest_stat = { |
| .idle_cpus = UINT_MAX, |
| .group_type = group_has_spare, |
| }, |
| }; |
| } |
| |
| static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu) |
| { |
| struct rq *rq = cpu_rq(cpu); |
| unsigned long max = arch_scale_cpu_capacity(cpu); |
| unsigned long used, free; |
| unsigned long irq; |
| |
| irq = cpu_util_irq(rq); |
| |
| if (unlikely(irq >= max)) |
| return 1; |
| |
| used = READ_ONCE(rq->avg_rt.util_avg); |
| used += READ_ONCE(rq->avg_dl.util_avg); |
| |
| if (unlikely(used >= max)) |
| return 1; |
| |
| free = max - used; |
| |
| return scale_irq_capacity(free, irq, max); |
| } |
| |
| static void update_cpu_capacity(struct sched_domain *sd, int cpu) |
| { |
| unsigned long capacity = scale_rt_capacity(sd, cpu); |
| struct sched_group *sdg = sd->groups; |
| |
| cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu); |
| |
| if (!capacity) |
| capacity = 1; |
| |
| cpu_rq(cpu)->cpu_capacity = capacity; |
| sdg->sgc->capacity = capacity; |
| sdg->sgc->min_capacity = capacity; |
| sdg->sgc->max_capacity = capacity; |
| } |
| |
| void update_group_capacity(struct sched_domain *sd, int cpu) |
| { |
| struct sched_domain *child = sd->child; |
| struct sched_group *group, *sdg = sd->groups; |
| unsigned long capacity, min_capacity, max_capacity; |
| unsigned long interval; |
| |
| interval = msecs_to_jiffies(sd->balance_interval); |
| interval = clamp(interval, 1UL, max_load_balance_interval); |
| sdg->sgc->next_update = jiffies + interval; |
| |
| if (!child) { |
| update_cpu_capacity(sd, cpu); |
| return; |
| } |
| |
| capacity = 0; |
| min_capacity = ULONG_MAX; |
| max_capacity = 0; |
| |
| if (child->flags & SD_OVERLAP) { |
| /* |
| * SD_OVERLAP domains cannot assume that child groups |
| * span the current group. |
| */ |
| |
| for_each_cpu(cpu, sched_group_span(sdg)) { |
| unsigned long cpu_cap = capacity_of(cpu); |
| |
| capacity += cpu_cap; |
| min_capacity = min(cpu_cap, min_capacity); |
| max_capacity = max(cpu_cap, max_capacity); |
| } |
| } else { |
| /* |
| * !SD_OVERLAP domains can assume that child groups |
| * span the current group. |
| */ |
| |
| group = child->groups; |
| do { |
| struct sched_group_capacity *sgc = group->sgc; |
| |
| capacity += sgc->capacity; |
| min_capacity = min(sgc->min_capacity, min_capacity); |
| max_capacity = max(sgc->max_capacity, max_capacity); |
| group = group->next; |
| } while (group != child->groups); |
| } |
| |
| sdg->sgc->capacity = capacity; |
| sdg->sgc->min_capacity = min_capacity; |
| sdg->sgc->max_capacity = max_capacity; |
| } |
| |
| /* |
| * Check whether the capacity of the rq has been noticeably reduced by side |
| * activity. The imbalance_pct is used for the threshold. |
| * Return true is the capacity is reduced |
| */ |
| static inline int |
| check_cpu_capacity(struct rq *rq, struct sched_domain *sd) |
| { |
| return ((rq->cpu_capacity * sd->imbalance_pct) < |
| (rq->cpu_capacity_orig * 100)); |
| } |
| |
| /* |
| * Check whether a rq has a misfit task and if it looks like we can actually |
| * help that task: we can migrate the task to a CPU of higher capacity, or |
| * the task's current CPU is heavily pressured. |
| */ |
| static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd) |
| { |
| return rq->misfit_task_load && |
| (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity || |
| check_cpu_capacity(rq, sd)); |
| } |
| |
| /* |
| * Group imbalance indicates (and tries to solve) the problem where balancing |
| * groups is inadequate due to ->cpus_ptr constraints. |
| * |
| * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a |
| * cpumask covering 1 CPU of the first group and 3 CPUs of the second group. |
| * Something like: |
| * |
| * { 0 1 2 3 } { 4 5 6 7 } |
| * * * * * |
| * |
| * If we were to balance group-wise we'd place two tasks in the first group and |
| * two tasks in the second group. Clearly this is undesired as it will overload |
| * cpu 3 and leave one of the CPUs in the second group unused. |
| * |
| * The current solution to this issue is detecting the skew in the first group |
| * by noticing the lower domain failed to reach balance and had difficulty |
| * moving tasks due to affinity constraints. |
| * |
| * When this is so detected; this group becomes a candidate for busiest; see |
| * update_sd_pick_busiest(). And calculate_imbalance() and |
| * find_busiest_group() avoid some of the usual balance conditions to allow it |
| * to create an effective group imbalance. |
| * |
| * This is a somewhat tricky proposition since the next run might not find the |
| * group imbalance and decide the groups need to be balanced again. A most |
| * subtle and fragile situation. |
| */ |
| |
| static inline int sg_imbalanced(struct sched_group *group) |
| { |
| return group->sgc->imbalance; |
| } |
| |
| /* |
| * group_has_capacity returns true if the group has spare capacity that could |
| * be used by some tasks. |
| * We consider that a group has spare capacity if the * number of task is |
| * smaller than the number of CPUs or if the utilization is lower than the |
| * available capacity for CFS tasks. |
| * For the latter, we use a threshold to stabilize the state, to take into |
| * account the variance of the tasks' load and to return true if the available |
| * capacity in meaningful for the load balancer. |
| * As an example, an available capacity of 1% can appear but it doesn't make |
| * any benefit for the load balance. |
| */ |
| static inline bool |
| group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs) |
| { |
| if (sgs->sum_nr_running < sgs->group_weight) |
| return true; |
| |
| if ((sgs->group_capacity * 100) > |
| (sgs->group_util * imbalance_pct)) |
| return true; |
| |
| return false; |
| } |
| |
| /* |
| * group_is_overloaded returns true if the group has more tasks than it can |
| * handle. |
| * group_is_overloaded is not equals to !group_has_capacity because a group |
| * with the exact right number of tasks, has no more spare capacity but is not |
| * overloaded so both group_has_capacity and group_is_overloaded return |
| * false. |
| */ |
| static inline bool |
| group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs) |
| { |
| if (sgs->sum_nr_running <= sgs->group_weight) |
| return false; |
| |
| if ((sgs->group_capacity * 100) < |
| (sgs->group_util * imbalance_pct)) |
| return true; |
| |
| return false; |
| } |
| |
| /* |
| * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller |
| * per-CPU capacity than sched_group ref. |
| */ |
| static inline bool |
| group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref) |
| { |
| return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity); |
| } |
| |
| /* |
| * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller |
| * per-CPU capacity_orig than sched_group ref. |
| */ |
| static inline bool |
| group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref) |
| { |
| return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity); |
| } |
| |
| static inline enum |
| group_type group_classify(unsigned int imbalance_pct, |
| struct sched_group *group, |
| struct sg_lb_stats *sgs) |
| { |
| if (group_is_overloaded(imbalance_pct, sgs)) |
| return group_overloaded; |
| |
| if (sg_imbalanced(group)) |
| return group_imbalanced; |
| |
| if (sgs->group_asym_packing) |
| return group_asym_packing; |
| |
| if (sgs->group_misfit_task_load) |
| return group_misfit_task; |
| |
| if (!group_has_capacity(imbalance_pct, sgs)) |
| return group_fully_busy; |
| |
| return group_has_spare; |
| } |
| |
| static bool update_nohz_stats(struct rq *rq, bool force) |
| { |
| #ifdef CONFIG_NO_HZ_COMMON |
| unsigned int cpu = rq->cpu; |
| |
| if (!rq->has_blocked_load) |
| return false; |
| |
| if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask)) |
| return false; |
| |
| if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick)) |
| return true; |
| |
| update_blocked_averages(cpu); |
| |
| return rq->has_blocked_load; |
| #else |
| return false; |
| #endif |
| } |
| |
| /** |
| * update_sg_lb_stats - Update sched_group's statistics for load balancing. |
| * @env: The load balancing environment. |
| * @group: sched_group whose statistics are to be updated. |
| * @sgs: variable to hold the statistics for this group. |
| * @sg_status: Holds flag indicating the status of the sched_group |
| */ |
| static inline void update_sg_lb_stats(struct lb_env *env, |
| struct sched_group *group, |
| struct sg_lb_stats *sgs, |
| int *sg_status) |
| { |
| int i, nr_running, local_group; |
| |
| memset(sgs, 0, sizeof(*sgs)); |
| |
| local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group)); |
| |
| for_each_cpu_and(i, sched_group_span(group), env->cpus) { |
| struct rq *rq = cpu_rq(i); |
| |
| if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false)) |
| env->flags |= LBF_NOHZ_AGAIN; |
| |
| sgs->group_load += cpu_load(rq); |
| sgs->group_util += cpu_util(i); |
| sgs->sum_h_nr_running += rq->cfs.h_nr_running; |
| |
| nr_running = rq->nr_running; |
| sgs->sum_nr_running += nr_running; |
| |
| if (nr_running > 1) |
| *sg_status |= SG_OVERLOAD; |
| |
| if (cpu_overutilized(i)) |
| *sg_status |= SG_OVERUTILIZED; |
| |
| #ifdef CONFIG_NUMA_BALANCING |
| sgs->nr_numa_running += rq->nr_numa_running; |
| sgs->nr_preferred_running += rq->nr_preferred_running; |
| #endif |
| /* |
| * No need to call idle_cpu() if nr_running is not 0 |
| */ |
| if (!nr_running && idle_cpu(i)) { |
| sgs->idle_cpus++; |
| /* Idle cpu can't have misfit task */ |
| continue; |
| } |
| |
| if (local_group) |
| continue; |
| |
| /* Check for a misfit task on the cpu */ |
| if (env->sd->flags & SD_ASYM_CPUCAPACITY && |
| sgs->group_misfit_task_load < rq->misfit_task_load) { |
| sgs->group_misfit_task_load = rq->misfit_task_load; |
| *sg_status |= SG_OVERLOAD; |
| } |
| } |
| |
| /* Check if dst CPU is idle and preferred to this group */ |
| if (env->sd->flags & SD_ASYM_PACKING && |
| env->idle != CPU_NOT_IDLE && |
| sgs->sum_h_nr_running && |
| sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) { |
| sgs->group_asym_packing = 1; |
| } |
| |
| sgs->group_capacity = group->sgc->capacity; |
| |
| sgs->group_weight = group->group_weight; |
| |
| sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs); |
| |
| /* Computing avg_load makes sense only when group is overloaded */ |
| if (sgs->group_type == group_overloaded) |
| sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) / |
| sgs->group_capacity; |
| } |
| |
| /** |
| * update_sd_pick_busiest - return 1 on busiest group |
| * @env: The load balancing environment. |
| * @sds: sched_domain statistics |
| * @sg: sched_group candidate to be checked for being the busiest |
| * @sgs: sched_group statistics |
| * |
| * Determine if @sg is a busier group than the previously selected |
| * busiest group. |
| * |
| * Return: %true if @sg is a busier group than the previously selected |
| * busiest group. %false otherwise. |
| */ |
| static bool update_sd_pick_busiest(struct lb_env *env, |
| struct sd_lb_stats *sds, |
| struct sched_group *sg, |
| struct sg_lb_stats *sgs) |
| { |
| struct sg_lb_stats *busiest = &sds->busiest_stat; |
| |
| /* Make sure that there is at least one task to pull */ |
| if (!sgs->sum_h_nr_running) |
| return false; |
| |
| /* |
| * Don't try to pull misfit tasks we can't help. |
| * We can use max_capacity here as reduction in capacity on some |
| * CPUs in the group should either be possible to resolve |
| * internally or be covered by avg_load imbalance (eventually). |
| */ |
| if (sgs->group_type == group_misfit_task && |
| (!group_smaller_max_cpu_capacity(sg, sds->local) || |
| sds->local_stat.group_type != group_has_spare)) |
| return false; |
| |
| if (sgs->group_type > busiest->group_type) |
| return true; |
| |
| if (sgs->group_type < busiest->group_type) |
| return false; |
| |
| /* |
| * The candidate and the current busiest group are the same type of |
| * group. Let check which one is the busiest according to the type. |
| */ |
| |
| switch (sgs->group_type) { |
| case group_overloaded: |
| /* Select the overloaded group with highest avg_load. */ |
| if (sgs->avg_load <= busiest->avg_load) |
| return false; |
| break; |
| |
| case group_imbalanced: |
| /* |
| * Select the 1st imbalanced group as we don't have any way to |
| * choose one more than another. |
| */ |
| return false; |
| |
| case group_asym_packing: |
| /* Prefer to move from lowest priority CPU's work */ |
| if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu)) |
| return false; |
| break; |
| |
| case group_misfit_task: |
| /* |
| * If we have more than one misfit sg go with the biggest |
| * misfit. |
| */ |
| if (sgs->group_misfit_task_load < busiest->group_misfit_task_load) |
| return false; |
| break; |
| |
| case group_fully_busy: |
| /* |
| * Select the fully busy group with highest avg_load. In |
| * theory, there is no need to pull task from such kind of |
| * group because tasks have all compute capacity that they need |
| * but we can still improve the overall throughput by reducing |
| * contention when accessing shared HW resources. |
| * |
| * XXX for now avg_load is not computed and always 0 so we |
| * select the 1st one. |
| */ |
| if (sgs->avg_load <= busiest->avg_load) |
| return false; |
| break; |
| |
| case group_has_spare: |
| /* |
| * Select not overloaded group with lowest number of idle cpus |
| * and highest number of running tasks. We could also compare |
| * the spare capacity which is more stable but it can end up |
| * that the group has less spare capacity but finally more idle |
| * CPUs which means less opportunity to pull tasks. |
| */ |
| if (sgs->idle_cpus > busiest->idle_cpus) |
| return false; |
| else if ((sgs->idle_cpus == busiest->idle_cpus) && |
| (sgs->sum_nr_running <= busiest->sum_nr_running)) |
| return false; |
| |
| break; |
| } |
| |
| /* |
| * Candidate sg has no more than one task per CPU and has higher |
| * per-CPU capacity. Migrating tasks to less capable CPUs may harm |
| * throughput. Maximize throughput, power/energy consequences are not |
| * considered. |
| */ |
| if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && |
| (sgs->group_type <= group_fully_busy) && |
| (group_smaller_min_cpu_capacity(sds->local, sg))) |
| return false; |
| |
| return true; |
| } |
| |
| #ifdef CONFIG_NUMA_BALANCING |
| static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) |
| { |
| if (sgs->sum_h_nr_running > sgs->nr_numa_running) |
| return regular; |
| if (sgs->sum_h_nr_running > sgs->nr_preferred_running) |
| return remote; |
| return all; |
| } |
| |
| static inline enum fbq_type fbq_classify_rq(struct rq *rq) |
| { |
| if (rq->nr_running > rq->nr_numa_running) |
| return regular; |
| if (rq->nr_running > rq->nr_preferred_running) |
| return remote; |
| return all; |
| } |
| #else |
| static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) |
| { |
| return all; |
| } |
| |
| static inline enum fbq_type fbq_classify_rq(struct rq *rq) |
| { |
| return regular; |
| } |
| #endif /* CONFIG_NUMA_BALANCING */ |
| |
| |
| struct sg_lb_stats; |
| |
| /* |
| * task_running_on_cpu - return 1 if @p is running on @cpu. |
| */ |
| |
| static unsigned int task_running_on_cpu(int cpu, struct task_struct *p) |
| { |
| /* Task has no contribution or is new */ |
| if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) |
| return 0; |
| |
| if (task_on_rq_queued(p)) |
| return 1; |
| |
| return 0; |
| } |
| |
| /** |
| * idle_cpu_without - would a given CPU be idle without p ? |
| * @cpu: the processor on which idleness is tested. |
| * @p: task which should be ignored. |
| * |
| * Return: 1 if the CPU would be idle. 0 otherwise. |
| */ |
| static int idle_cpu_without(int cpu, struct task_struct *p) |
| { |
| struct rq *rq = cpu_rq(cpu); |
| |
| if (rq->curr != rq->idle && rq->curr != p) |
| return 0; |
| |
| /* |
| * rq->nr_running can't be used but an updated version without the |
| * impact of p on cpu must be used instead. The updated nr_running |
| * be computed and tested before calling idle_cpu_without(). |
| */ |
| |
| #ifdef CONFIG_SMP |
| if (!llist_empty(&rq->wake_list)) |
| return 0; |
| #endif |
| |
| return 1; |
| } |
| |
| /* |
| * update_sg_wakeup_stats - Update sched_group's statistics for wakeup. |
| * @sd: The sched_domain level to look for idlest group. |
| * @group: sched_group whose statistics are to be updated. |
| * @sgs: variable to hold the statistics for this group. |
| * @p: The task for which we look for the idlest group/CPU. |
| */ |
| static inline void update_sg_wakeup_stats(struct sched_domain *sd, |
| struct sched_group *group, |
| struct sg_lb_stats *sgs, |
| struct task_struct *p) |
| { |
| int i, nr_running; |
| |
| memset(sgs, 0, sizeof(*sgs)); |
| |
| for_each_cpu(i, sched_group_span(group)) { |
| struct rq *rq = cpu_rq(i); |
| unsigned int local; |
| |
| sgs->group_load += cpu_load_without(rq, p); |
| sgs->group_util += cpu_util_without(i, p); |
| local = task_running_on_cpu(i, p); |
| sgs->sum_h_nr_running += rq->cfs.h_nr_running - local; |
| |
| nr_running = rq->nr_running - local; |
| sgs->sum_nr_running += nr_running; |
| |
| /* |
| * No need to call idle_cpu_without() if nr_running is not 0 |
| */ |
| if (!nr_running && idle_cpu_without(i, p)) |
| sgs->idle_cpus++; |
| |
| } |
| |
| /* Check if task fits in the group */ |
| if (sd->flags & SD_ASYM_CPUCAPACITY && |
| !task_fits_capacity(p, group->sgc->max_capacity)) { |
| sgs->group_misfit_task_load = 1; |
| } |
| |
| sgs->group_capacity = group->sgc->capacity; |
| |
| sgs->group_type = group_classify(sd->imbalance_pct, group, sgs); |
| |
| /* |
| * Computing avg_load makes sense only when group is fully busy or |
| * overloaded |
| */ |
| if (sgs->group_type < group_fully_busy) |
| sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) / |
| sgs->group_capacity; |
| } |
| |
| static bool update_pick_idlest(struct sched_group *idlest, |
| struct sg_lb_stats *idlest_sgs, |
| struct sched_group *group, |
| struct sg_lb_stats *sgs) |
| { |
| if (sgs->group_type < idlest_sgs->group_type) |
| return true; |
| |
| if (sgs->group_type > idlest_sgs->group_type) |
| return false; |
| |
| /* |
| * The candidate and the current idlest group are the same type of |
| * group. Let check which one is the idlest according to the type. |
| */ |
| |
| switch (sgs->group_type) { |
| case group_overloaded: |
| case group_fully_busy: |
| /* Select the group with lowest avg_load. */ |
| if (idlest_sgs->avg_load <= sgs->avg_load) |
| return false; |
| break; |
| |
| case group_imbalanced: |
| case group_asym_packing: |
| /* Those types are not used in the slow wakeup path */ |
| return false; |
| |
| case group_misfit_task: |
| /* Select group with the highest max capacity */ |
| if (idlest->sgc->max_capacity >= group->sgc->max_capacity) |
| return false; |
| break; |
| |
| case group_has_spare: |
| /* Select group with most idle CPUs */ |
| if (idlest_sgs->idle_cpus >= sgs->idle_cpus) |
| return false; |
| break; |
| } |
| |
| return true; |
| } |
| |
| /* |
| * find_idlest_group() finds and returns the least busy CPU group within the |
| * domain. |
| * |
| * Assumes p is allowed on at least one CPU in sd. |
| */ |
| static struct sched_group * |
| find_idlest_group(struct sched_domain *sd, struct task_struct *p, |
| int this_cpu, int sd_flag) |
| { |
| struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups; |
| struct sg_lb_stats local_sgs, tmp_sgs; |
| struct sg_lb_stats *sgs; |
| unsigned long imbalance; |
| struct sg_lb_stats idlest_sgs = { |
| .avg_load = UINT_MAX, |
| .group_type = group_overloaded, |
| }; |
| |
| imbalance = scale_load_down(NICE_0_LOAD) * |
| (sd->imbalance_pct-100) / 100; |
| |
| do { |
| int local_group; |
| |
| /* Skip over this group if it has no CPUs allowed */ |
| if (!cpumask_intersects(sched_group_span(group), |
| p->cpus_ptr)) |
| continue; |
| |
| local_group = cpumask_test_cpu(this_cpu, |
| sched_group_span(group)); |
| |
| if (local_group) { |
| sgs = &local_sgs; |
| local = group; |
| } else { |
| sgs = &tmp_sgs; |
| } |
| |
| update_sg_wakeup_stats(sd, group, sgs, p); |
| |
| if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) { |
| idlest = group; |
| idlest_sgs = *sgs; |
| } |
| |
| } while (group = group->next, group != sd->groups); |
| |
| |
| /* There is no idlest group to push tasks to */ |
| if (!idlest) |
| return NULL; |
| |
| /* The local group has been skipped because of CPU affinity */ |
| if (!local) |
| return idlest; |
| |
| /* |
| * If the local group is idler than the selected idlest group |
| * don't try and push the task. |
| */ |
| if (local_sgs.group_type < idlest_sgs.group_type) |
| return NULL; |
| |
| /* |
| * If the local group is busier than the selected idlest group |
| * try and push the task. |
| */ |
| if (local_sgs.group_type > idlest_sgs.group_type) |
| return idlest; |
| |
| switch (local_sgs.group_type) { |
| case group_overloaded: |
| case group_fully_busy: |
| /* |
| * When comparing groups across NUMA domains, it's possible for |
| * the local domain to be very lightly loaded relative to the |
| * remote domains but "imbalance" skews the comparison making |
| * remote CPUs look much more favourable. When considering |
| * cross-domain, add imbalance to the load on the remote node |
| * and consider staying local. |
| */ |
| |
| if ((sd->flags & SD_NUMA) && |
| ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load)) |
| return NULL; |
| |
| /* |
| * If the local group is less loaded than the selected |
| * idlest group don't try and push any tasks. |
| */ |
| if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance)) |
| return NULL; |
| |
| if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load) |
| return NULL; |
| break; |
| |
| case group_imbalanced: |
| case group_asym_packing: |
| /* Those type are not used in the slow wakeup path */ |
| return NULL; |
| |
| case group_misfit_task: |
| /* Select group with the highest max capacity */ |
| if (local->sgc->max_capacity >= idlest->sgc->max_capacity) |
| return NULL; |
| break; |
| |
| case group_has_spare: |
| if (sd->flags & SD_NUMA) { |
| #ifdef CONFIG_NUMA_BALANCING |
| int idlest_cpu; |
| /* |
| * If there is spare capacity at NUMA, try to select |
| * the preferred node |
| */ |
| if (cpu_to_node(this_cpu) == p->numa_preferred_nid) |
| return NULL; |
| |
| idlest_cpu = cpumask_first(sched_group_span(idlest)); |
| if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid) |
| return idlest; |
| #endif |
| /* |
| * Otherwise, keep the task on this node to stay close |
| * its wakeup source and improve locality. If there is |
| * a real need of migration, periodic load balance will |
| * take care of it. |
| */ |
| if (local_sgs.idle_cpus) |
| return NULL; |
| } |
| |
| /* |
| * Select group with highest number of idle CPUs. We could also |
| * compare the utilization which is more stable but it can end |
| * up that the group has less spare capacity but finally more |
| * idle CPUs which means more opportunity to run task. |
| */ |
| if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus) |
| return NULL; |
| break; |
| } |
| |
| return idlest; |
| } |
| |
| /** |
| * update_sd_lb_stats - Update sched_domain's statistics for load balancing. |
| * @env: The load balancing environment. |
| * @sds: variable to hold the statistics for this sched_domain. |
| */ |
| |
| static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) |
| { |
| struct sched_domain *child = env->sd->child; |
| struct sched_group *sg = env->sd->groups; |
| struct sg_lb_stats *local = &sds->local_stat; |
| struct sg_lb_stats tmp_sgs; |
| int sg_status = 0; |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked)) |
| env->flags |= LBF_NOHZ_STATS; |
| #endif |
| |
| do { |
| struct sg_lb_stats *sgs = &tmp_sgs; |
| int local_group; |
| |
| local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg)); |
| if (local_group) { |
| sds->local = sg; |
| sgs = local; |
| |
| if (env->idle != CPU_NEWLY_IDLE || |
| time_after_eq(jiffies, sg->sgc->next_update)) |
| update_group_capacity(env->sd, env->dst_cpu); |
| } |
| |
| update_sg_lb_stats(env, sg, sgs, &sg_status); |
| |
| if (local_group) |
| goto next_group; |
| |
| |
| if (update_sd_pick_busiest(env, sds, sg, sgs)) { |
| sds->busiest = sg; |
| sds->busiest_stat = *sgs; |
| } |
| |
| next_group: |
| /* Now, start updating sd_lb_stats */ |
| sds->total_load += sgs->group_load; |
| sds->total_capacity += sgs->group_capacity; |
| |
| sg = sg->next; |
| } while (sg != env->sd->groups); |
| |
| /* Tag domain that child domain prefers tasks go to siblings first */ |
| sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING; |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| if ((env->flags & LBF_NOHZ_AGAIN) && |
| cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) { |
| |
| WRITE_ONCE(nohz.next_blocked, |
| jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD)); |
| } |
| #endif |
| |
| if (env->sd->flags & SD_NUMA) |
| env->fbq_type = fbq_classify_group(&sds->busiest_stat); |
| |
| if (!env->sd->parent) { |
| struct root_domain *rd = env->dst_rq->rd; |
| |
| /* update overload indicator if we are at root domain */ |
| WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD); |
| |
| /* Update over-utilization (tipping point, U >= 0) indicator */ |
| WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED); |
| trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED); |
| } else if (sg_status & SG_OVERUTILIZED) { |
| struct root_domain *rd = env->dst_rq->rd; |
| |
| WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED); |
| trace_sched_overutilized_tp(rd, SG_OVERUTILIZED); |
| } |
| } |
| |
| /** |
| * calculate_imbalance - Calculate the amount of imbalance present within the |
| * groups of a given sched_domain during load balance. |
| * @env: load balance environment |
| * @sds: statistics of the sched_domain whose imbalance is to be calculated. |
| */ |
| static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) |
| { |
| struct sg_lb_stats *local, *busiest; |
| |
| local = &sds->local_stat; |
| busiest = &sds->busiest_stat; |
| |
| if (busiest->group_type == group_misfit_task) { |
| /* Set imbalance to allow misfit tasks to be balanced. */ |
| env->migration_type = migrate_misfit; |
| env->imbalance = 1; |
| return; |
| } |
| |
| if (busiest->group_type == group_asym_packing) { |
| /* |
| * In case of asym capacity, we will try to migrate all load to |
| * the preferred CPU. |
| */ |
| env->migration_type = migrate_task; |
| env->imbalance = busiest->sum_h_nr_running; |
| return; |
| } |
| |
| if (busiest->group_type == group_imbalanced) { |
| /* |
| * In the group_imb case we cannot rely on group-wide averages |
| * to ensure CPU-load equilibrium, try to move any task to fix |
| * the imbalance. The next load balance will take care of |
| * balancing back the system. |
| */ |
| env->migration_type = migrate_task; |
| env->imbalance = 1; |
| return; |
| } |
| |
| /* |
| * Try to use spare capacity of local group without overloading it or |
| * emptying busiest. |
| * XXX Spreading tasks across NUMA nodes is not always the best policy |
| * and special care should be taken for SD_NUMA domain level before |
| * spreading the tasks. For now, load_balance() fully relies on |
| * NUMA_BALANCING and fbq_classify_group/rq to override the decision. |
| */ |
| if (local->group_type == group_has_spare) { |
| if (busiest->group_type > group_fully_busy) { |
| /* |
| * If busiest is overloaded, try to fill spare |
| * capacity. This might end up creating spare capacity |
| * in busiest or busiest still being overloaded but |
| * there is no simple way to directly compute the |
| * amount of load to migrate in order to balance the |
| * system. |
| */ |
| env->migration_type = migrate_util; |
| env->imbalance = max(local->group_capacity, local->group_util) - |
| local->group_util; |
| |
| /* |
| * In some cases, the group's utilization is max or even |
| * higher than capacity because of migrations but the |
| * local CPU is (newly) idle. There is at least one |
| * waiting task in this overloaded busiest group. Let's |
| * try to pull it. |
| */ |
| if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) { |
| env->migration_type = migrate_task; |
| env->imbalance = 1; |
| } |
| |
| return; |
| } |
| |
| if (busiest->group_weight == 1 || sds->prefer_sibling) { |
| unsigned int nr_diff = busiest->sum_nr_running; |
| /* |
| * When prefer sibling, evenly spread running tasks on |
| * groups. |
| */ |
| env->migration_type = migrate_task; |
| lsub_positive(&nr_diff, local->sum_nr_running); |
| env->imbalance = nr_diff >> 1; |
| return; |
| } |
| |
| /* |
| * If there is no overload, we just want to even the number of |
| * idle cpus. |
| */ |
| env->migration_type = migrate_task; |
| env->imbalance = max_t(long, 0, (local->idle_cpus - |
| busiest->idle_cpus) >> 1); |
| return; |
| } |
| |
| /* |
| * Local is fully busy but has to take more load to relieve the |
| * busiest group |
| */ |
| if (local->group_type < group_overloaded) { |
| /* |
| * Local will become overloaded so the avg_load metrics are |
| * finally needed. |
| */ |
| |
| local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) / |
| local->group_capacity; |
| |
| sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) / |
| sds->total_capacity; |
| } |
| |
| /* |
| * Both group are or will become overloaded and we're trying to get all |
| * the CPUs to the average_load, so we don't want to push ourselves |
| * above the average load, nor do we wish to reduce the max loaded CPU |
| * below the average load. At the same time, we also don't want to |
| * reduce the group load below the group capacity. Thus we look for |
| * the minimum possible imbalance. |
| */ |
| env->migration_type = migrate_load; |
| env->imbalance = min( |
| (busiest->avg_load - sds->avg_load) * busiest->group_capacity, |
| (sds->avg_load - local->avg_load) * local->group_capacity |
| ) / SCHED_CAPACITY_SCALE; |
| } |
| |
| /******* find_busiest_group() helpers end here *********************/ |
| |
| /* |
| * Decision matrix according to the local and busiest group type: |
| * |
| * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded |
| * has_spare nr_idle balanced N/A N/A balanced balanced |
| * fully_busy nr_idle nr_idle N/A N/A balanced balanced |
| * misfit_task force N/A N/A N/A force force |
| * asym_packing force force N/A N/A force force |
| * imbalanced force force N/A N/A force force |
| * overloaded force force N/A N/A force avg_load |
| * |
| * N/A : Not Applicable because already filtered while updating |
| * statistics. |
| * balanced : The system is balanced for these 2 groups. |
| * force : Calculate the imbalance as load migration is probably needed. |
| * avg_load : Only if imbalance is significant enough. |
| * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite |
| * different in groups. |
| */ |
| |
| /** |
| * find_busiest_group - Returns the busiest group within the sched_domain |
| * if there is an imbalance. |
| * |
| * Also calculates the amount of runnable load which should be moved |
| * to restore balance. |
| * |
| * @env: The load balancing environment. |
| * |
| * Return: - The busiest group if imbalance exists. |
| */ |
| static struct sched_group *find_busiest_group(struct lb_env *env) |
| { |
| struct sg_lb_stats *local, *busiest; |
| struct sd_lb_stats sds; |
| |
| init_sd_lb_stats(&sds); |
| |
| /* |
| * Compute the various statistics relevant for load balancing at |
| * this level. |
| */ |
| update_sd_lb_stats(env, &sds); |
| |
| if (sched_energy_enabled()) { |
| struct root_domain *rd = env->dst_rq->rd; |
| |
| if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized)) |
| goto out_balanced; |
| } |
| |
| local = &sds.local_stat; |
| busiest = &sds.busiest_stat; |
| |
| /* There is no busy sibling group to pull tasks from */ |
| if (!sds.busiest) |
| goto out_balanced; |
| |
| /* Misfit tasks should be dealt with regardless of the avg load */ |
| if (busiest->group_type == group_misfit_task) |
| goto force_balance; |
| |
| /* ASYM feature bypasses nice load balance check */ |
| if (busiest->group_type == group_asym_packing) |
| goto force_balance; |
| |
| /* |
| * If the busiest group is imbalanced the below checks don't |
| * work because they assume all things are equal, which typically |
| * isn't true due to cpus_ptr constraints and the like. |
| */ |
| if (busiest->group_type == group_imbalanced) |
| goto force_balance; |
| |
| /* |
| * If the local group is busier than the selected busiest group |
| * don't try and pull any tasks. |
| */ |
| if (local->group_type > busiest->group_type) |
| goto out_balanced; |
| |
| /* |
| * When groups are overloaded, use the avg_load to ensure fairness |
| * between tasks. |
| */ |
| if (local->group_type == group_overloaded) { |
| /* |
| * If the local group is more loaded than the selected |
| * busiest group don't try to pull any tasks. |
| */ |
| if (local->avg_load >= busiest->avg_load) |
| goto out_balanced; |
| |
| /* XXX broken for overlapping NUMA groups */ |
| sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) / |
| sds.total_capacity; |
| |
| /* |
| * Don't pull any tasks if this group is already above the |
| * domain average load. |
| */ |
| if (local->avg_load >= sds.avg_load) |
| goto out_balanced; |
| |
| /* |
| * If the busiest group is more loaded, use imbalance_pct to be |
| * conservative. |
| */ |
| if (100 * busiest->avg_load <= |
| env->sd->imbalance_pct * local->avg_load) |
| goto out_balanced; |
| } |
| |
| /* Try to move all excess tasks to child's sibling domain */ |
| if (sds.prefer_sibling && local->group_type == group_has_spare && |
| busiest->sum_nr_running > local->sum_nr_running + 1) |
| goto force_balance; |
| |
| if (busiest->group_type != group_overloaded) { |
| if (env->idle == CPU_NOT_IDLE) |
| /* |
| * If the busiest group is not overloaded (and as a |
| * result the local one too) but this CPU is already |
| * busy, let another idle CPU try to pull task. |
| */ |
| goto out_balanced; |
| |
| if (busiest->group_weight > 1 && |
| local->idle_cpus <= (busiest->idle_cpus + 1)) |
| /* |
| * If the busiest group is not overloaded |
| * and there is no imbalance between this and busiest |
| * group wrt idle CPUs, it is balanced. The imbalance |
| * becomes significant if the diff is greater than 1 |
| * otherwise we might end up to just move the imbalance |
| * on another group. Of course this applies only if |
| * there is more than 1 CPU per group. |
| */ |
| goto out_balanced; |
| |
| if (busiest->sum_h_nr_running == 1) |
| /* |
| * busiest doesn't have any tasks waiting to run |
| */ |
| goto out_balanced; |
| } |
| |
| force_balance: |
| /* Looks like there is an imbalance. Compute it */ |
| calculate_imbalance(env, &sds); |
| return env->imbalance ? sds.busiest : NULL; |
| |
| out_balanced: |
| env->imbalance = 0; |
| return NULL; |
| } |
| |
| /* |
| * find_busiest_queue - find the busiest runqueue among the CPUs in the group. |
| */ |
| static struct rq *find_busiest_queue(struct lb_env *env, |
| struct sched_group *group) |
| { |
| struct rq *busiest = NULL, *rq; |
| unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1; |
| unsigned int busiest_nr = 0; |
| int i; |
| |
| for_each_cpu_and(i, sched_group_span(group), env->cpus) { |
| unsigned long capacity, load, util; |
| unsigned int nr_running; |
| enum fbq_type rt; |
| |
| rq = cpu_rq(i); |
| rt = fbq_classify_rq(rq); |
| |
| /* |
| * We classify groups/runqueues into three groups: |
| * - regular: there are !numa tasks |
| * - remote: there are numa tasks that run on the 'wrong' node |
| * - all: there is no distinction |
| * |
| * In order to avoid migrating ideally placed numa tasks, |
| * ignore those when there's better options. |
| * |
| * If we ignore the actual busiest queue to migrate another |
| * task, the next balance pass can still reduce the busiest |
| * queue by moving tasks around inside the node. |
| * |
| * If we cannot move enough load due to this classification |
| * the next pass will adjust the group classification and |
| * allow migration of more tasks. |
| * |
| * Both cases only affect the total convergence complexity. |
| */ |
| if (rt > env->fbq_type) |
| continue; |
| |
| capacity = capacity_of(i); |
| nr_running = rq->cfs.h_nr_running; |
| |
| /* |
| * For ASYM_CPUCAPACITY domains, don't pick a CPU that could |
| * eventually lead to active_balancing high->low capacity. |
| * Higher per-CPU capacity is considered better than balancing |
| * average load. |
| */ |
| if (env->sd->flags & SD_ASYM_CPUCAPACITY && |
| capacity_of(env->dst_cpu) < capacity && |
| nr_running == 1) |
| continue; |
| |
| switch (env->migration_type) { |
| case migrate_load: |
| /* |
| * When comparing with load imbalance, use cpu_load() |
| * which is not scaled with the CPU capacity. |
| */ |
| load = cpu_load(rq); |
| |
| if (nr_running == 1 && load > env->imbalance && |
| !check_cpu_capacity(rq, env->sd)) |
| break; |
| |
| /* |
| * For the load comparisons with the other CPUs, |
| * consider the cpu_load() scaled with the CPU |
| * capacity, so that the load can be moved away |
| * from the CPU that is potentially running at a |
| * lower capacity. |
| * |
| * Thus we're looking for max(load_i / capacity_i), |
| * crosswise multiplication to rid ourselves of the |
| * division works out to: |
| * load_i * capacity_j > load_j * capacity_i; |
| * where j is our previous maximum. |
| */ |
| if (load * busiest_capacity > busiest_load * capacity) { |
| busiest_load = load; |
| busiest_capacity = capacity; |
| busiest = rq; |
| } |
| break; |
| |
| case migrate_util: |
| util = cpu_util(cpu_of(rq)); |
| |
| if (busiest_util < util) { |
| busiest_util = util; |
| busiest = rq; |
| } |
| break; |
| |
| case migrate_task: |
| if (busiest_nr < nr_running) { |
| busiest_nr = nr_running; |
| busiest = rq; |
| } |
| break; |
| |
| case migrate_misfit: |
| /* |
| * For ASYM_CPUCAPACITY domains with misfit tasks we |
| * simply seek the "biggest" misfit task. |
| */ |
| if (rq->misfit_task_load > busiest_load) { |
| busiest_load = rq->misfit_task_load; |
| busiest = rq; |
| } |
| |
| break; |
| |
| } |
| } |
| |
| return busiest; |
| } |
| |
| /* |
| * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but |
| * so long as it is large enough. |
| */ |
| #define MAX_PINNED_INTERVAL 512 |
| |
| static inline bool |
| asym_active_balance(struct lb_env *env) |
| { |
| /* |
| * ASYM_PACKING needs to force migrate tasks from busy but |
| * lower priority CPUs in order to pack all tasks in the |
| * highest priority CPUs. |
| */ |
| return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) && |
| sched_asym_prefer(env->dst_cpu, env->src_cpu); |
| } |
| |
| static inline bool |
| voluntary_active_balance(struct lb_env *env) |
| { |
| struct sched_domain *sd = env->sd; |
| |
| if (asym_active_balance(env)) |
| return 1; |
| |
| /* |
| * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task. |
| * It's worth migrating the task if the src_cpu's capacity is reduced |
| * because of other sched_class or IRQs if more capacity stays |
| * available on dst_cpu. |
| */ |
| if ((env->idle != CPU_NOT_IDLE) && |
| (env->src_rq->cfs.h_nr_running == 1)) { |
| if ((check_cpu_capacity(env->src_rq, sd)) && |
| (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100)) |
| return 1; |
| } |
| |
| if (env->migration_type == migrate_misfit) |
| return 1; |
| |
| return 0; |
| } |
| |
| static int need_active_balance(struct lb_env *env) |
| { |
| struct sched_domain *sd = env->sd; |
| |
| if (voluntary_active_balance(env)) |
| return 1; |
| |
| return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); |
| } |
| |
| static int active_load_balance_cpu_stop(void *data); |
| |
| static int should_we_balance(struct lb_env *env) |
| { |
| struct sched_group *sg = env->sd->groups; |
| int cpu, balance_cpu = -1; |
| |
| /* |
| * Ensure the balancing environment is consistent; can happen |
| * when the softirq triggers 'during' hotplug. |
| */ |
| if (!cpumask_test_cpu(env->dst_cpu, env->cpus)) |
| return 0; |
| |
| /* |
| * In the newly idle case, we will allow all the CPUs |
| * to do the newly idle load balance. |
| */ |
| if (env->idle == CPU_NEWLY_IDLE) |
| return 1; |
| |
| /* Try to find first idle CPU */ |
| for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) { |
| if (!idle_cpu(cpu)) |
| continue; |
| |
| balance_cpu = cpu; |
| break; |
| } |
| |
| if (balance_cpu == -1) |
| balance_cpu = group_balance_cpu(sg); |
| |
| /* |
| * First idle CPU or the first CPU(busiest) in this sched group |
| * is eligible for doing load balancing at this and above domains. |
| */ |
| return balance_cpu == env->dst_cpu; |
| } |
| |
| /* |
| * Check this_cpu to ensure it is balanced within domain. Attempt to move |
| * tasks if there is an imbalance. |
| */ |
| static int load_balance(int this_cpu, struct rq *this_rq, |
| struct sched_domain *sd, enum cpu_idle_type idle, |
| int *continue_balancing) |
| { |
| int ld_moved, cur_ld_moved, active_balance = 0; |
| struct sched_domain *sd_parent = sd->parent; |
| struct sched_group *group; |
| struct rq *busiest; |
| struct rq_flags rf; |
| struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask); |
| |
| struct lb_env env = { |
| .sd = sd, |
| .dst_cpu = this_cpu, |
| .dst_rq = this_rq, |
| .dst_grpmask = sched_group_span(sd->groups), |
| .idle = idle, |
| .loop_break = sched_nr_migrate_break, |
| .cpus = cpus, |
| .fbq_type = all, |
| .tasks = LIST_HEAD_INIT(env.tasks), |
| }; |
| |
| cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); |
| |
| schedstat_inc(sd->lb_count[idle]); |
| |
| redo: |
| if (!should_we_balance(&env)) { |
| *continue_balancing = 0; |
| goto out_balanced; |
| } |
| |
| group = find_busiest_group(&env); |
| if (!group) { |
| schedstat_inc(sd->lb_nobusyg[idle]); |
| goto out_balanced; |
| } |
| |
| busiest = find_busiest_queue(&env, group); |
| if (!busiest) { |
| schedstat_inc(sd->lb_nobusyq[idle]); |
| goto out_balanced; |
| } |
| |
| BUG_ON(busiest == env.dst_rq); |
| |
| schedstat_add(sd->lb_imbalance[idle], env.imbalance); |
| |
| env.src_cpu = busiest->cpu; |
| env.src_rq = busiest; |
| |
| ld_moved = 0; |
| if (busiest->nr_running > 1) { |
| /* |
| * Attempt to move tasks. If find_busiest_group has found |
| * an imbalance but busiest->nr_running <= 1, the group is |
| * still unbalanced. ld_moved simply stays zero, so it is |
| * correctly treated as an imbalance. |
| */ |
| env.flags |= LBF_ALL_PINNED; |
| env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); |
| |
| more_balance: |
| rq_lock_irqsave(busiest, &rf); |
| update_rq_clock(busiest); |
| |
| /* |
| * cur_ld_moved - load moved in current iteration |
| * ld_moved - cumulative load moved across iterations |
| */ |
| cur_ld_moved = detach_tasks(&env); |
| |
| /* |
| * We've detached some tasks from busiest_rq. Every |
| * task is masked "TASK_ON_RQ_MIGRATING", so we can safely |
| * unlock busiest->lock, and we are able to be sure |
| * that nobody can manipulate the tasks in parallel. |
| * See task_rq_lock() family for the details. |
| */ |
| |
| rq_unlock(busiest, &rf); |
| |
| if (cur_ld_moved) { |
| attach_tasks(&env); |
| ld_moved += cur_ld_moved; |
| } |
| |
| local_irq_restore(rf.flags); |
| |
| if (env.flags & LBF_NEED_BREAK) { |
| env.flags &= ~LBF_NEED_BREAK; |
| goto more_balance; |
| } |
| |
| /* |
| * Revisit (affine) tasks on src_cpu that couldn't be moved to |
| * us and move them to an alternate dst_cpu in our sched_group |
| * where they can run. The upper limit on how many times we |
| * iterate on same src_cpu is dependent on number of CPUs in our |
| * sched_group. |
| * |
| * This changes load balance semantics a bit on who can move |
| * load to a given_cpu. In addition to the given_cpu itself |
| * (or a ilb_cpu acting on its behalf where given_cpu is |
| * nohz-idle), we now have balance_cpu in a position to move |
| * load to given_cpu. In rare situations, this may cause |
| * conflicts (balance_cpu and given_cpu/ilb_cpu deciding |
| * _independently_ and at _same_ time to move some load to |
| * given_cpu) causing exceess load to be moved to given_cpu. |
| * This however should not happen so much in practice and |
| * moreover subsequent load balance cycles should correct the |
| * excess load moved. |
| */ |
| if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) { |
| |
| /* Prevent to re-select dst_cpu via env's CPUs */ |
| __cpumask_clear_cpu(env.dst_cpu, env.cpus); |
| |
| env.dst_rq = cpu_rq(env.new_dst_cpu); |
| env.dst_cpu = env.new_dst_cpu; |
| env.flags &= ~LBF_DST_PINNED; |
| env.loop = 0; |
| env.loop_break = sched_nr_migrate_break; |
| |
| /* |
| * Go back to "more_balance" rather than "redo" since we |
| * need to continue with same src_cpu. |
| */ |
| goto more_balance; |
| } |
| |
| /* |
| * We failed to reach balance because of affinity. |
| */ |
| if (sd_parent) { |
| int *group_imbalance = &sd_parent->groups->sgc->imbalance; |
| |
| if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) |
| *group_imbalance = 1; |
| } |
| |
| /* All tasks on this runqueue were pinned by CPU affinity */ |
| if (unlikely(env.flags & LBF_ALL_PINNED)) { |
| __cpumask_clear_cpu(cpu_of(busiest), cpus); |
| /* |
| * Attempting to continue load balancing at the current |
| * sched_domain level only makes sense if there are |
| * active CPUs remaining as possible busiest CPUs to |
| * pull load from which are not contained within the |
| * destination group that is receiving any migrated |
| * load. |
| */ |
| if (!cpumask_subset(cpus, env.dst_grpmask)) { |
| env.loop = 0; |
| env.loop_break = sched_nr_migrate_break; |
| goto redo; |
| } |
| goto out_all_pinned; |
| } |
| } |
| |
| if (!ld_moved) { |
| schedstat_inc(sd->lb_failed[idle]); |
| /* |
| * Increment the failure counter only on periodic balance. |
| * We do not want newidle balance, which can be very |
| * frequent, pollute the failure counter causing |
| * excessive cache_hot migrations and active balances. |
| */ |
| if (idle != CPU_NEWLY_IDLE) |
| sd->nr_balance_failed++; |
| |
| if (need_active_balance(&env)) { |
| unsigned long flags; |
| |
| raw_spin_lock_irqsave(&busiest->lock, flags); |
| |
| /* |
| * Don't kick the active_load_balance_cpu_stop, |
| * if the curr task on busiest CPU can't be |
| * moved to this_cpu: |
| */ |
| if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) { |
| raw_spin_unlock_irqrestore(&busiest->lock, |
| flags); |
| env.flags |= LBF_ALL_PINNED; |
| goto out_one_pinned; |
| } |
| |
| /* |
| * ->active_balance synchronizes accesses to |
| * ->active_balance_work. Once set, it's cleared |
| * only after active load balance is finished. |
| */ |
| if (!busiest->active_balance) { |
| busiest->active_balance = 1; |
| busiest->push_cpu = this_cpu; |
| active_balance = 1; |
| } |
| raw_spin_unlock_irqrestore(&busiest->lock, flags); |
| |
| if (active_balance) { |
| stop_one_cpu_nowait(cpu_of(busiest), |
| active_load_balance_cpu_stop, busiest, |
| &busiest->active_balance_work); |
| } |
| |
| /* We've kicked active balancing, force task migration. */ |
| sd->nr_balance_failed = sd->cache_nice_tries+1; |
| } |
| } else |
| sd->nr_balance_failed = 0; |
| |
| if (likely(!active_balance) || voluntary_active_balance(&env)) { |
| /* We were unbalanced, so reset the balancing interval */ |
| sd->balance_interval = sd->min_interval; |
| } else { |
| /* |
| * If we've begun active balancing, start to back off. This |
| * case may not be covered by the all_pinned logic if there |
| * is only 1 task on the busy runqueue (because we don't call |
| * detach_tasks). |
| */ |
| if (sd->balance_interval < sd->max_interval) |
| sd->balance_interval *= 2; |
| } |
| |
| goto out; |
| |
| out_balanced: |
| /* |
| * We reach balance although we may have faced some affinity |
| * constraints. Clear the imbalance flag only if other tasks got |
| * a chance to move and fix the imbalance. |
| */ |
| if (sd_parent && !(env.flags & LBF_ALL_PINNED)) { |
| int *group_imbalance = &sd_parent->groups->sgc->imbalance; |
| |
| if (*group_imbalance) |
| *group_imbalance = 0; |
| } |
| |
| out_all_pinned: |
| /* |
| * We reach balance because all tasks are pinned at this level so |
| * we can't migrate them. Let the imbalance flag set so parent level |
| * can try to migrate them. |
| */ |
| schedstat_inc(sd->lb_balanced[idle]); |
| |
| sd->nr_balance_failed = 0; |
| |
| out_one_pinned: |
| ld_moved = 0; |
| |
| /* |
| * newidle_balance() disregards balance intervals, so we could |
| * repeatedly reach this code, which would lead to balance_interval |
| * skyrocketting in a short amount of time. Skip the balance_interval |
| * increase logic to avoid that. |
| */ |
| if (env.idle == CPU_NEWLY_IDLE) |
| goto out; |
| |
| /* tune up the balancing interval */ |
| if ((env.flags & LBF_ALL_PINNED && |
| sd->balance_interval < MAX_PINNED_INTERVAL) || |
| sd->balance_interval < sd->max_interval) |
| sd->balance_interval *= 2; |
| out: |
| return ld_moved; |
| } |
| |
| static inline unsigned long |
| get_sd_balance_interval(struct sched_domain *sd, int cpu_busy) |
| { |
| unsigned long interval = sd->balance_interval; |
| |
| if (cpu_busy) |
| interval *= sd->busy_factor; |
| |
| /* scale ms to jiffies */ |
| interval = msecs_to_jiffies(interval); |
| interval = clamp(interval, 1UL, max_load_balance_interval); |
| |
| return interval; |
| } |
| |
| static inline void |
| update_next_balance(struct sched_domain *sd, unsigned long *next_balance) |
| { |
| unsigned long interval, next; |
| |
| /* used by idle balance, so cpu_busy = 0 */ |
| interval = get_sd_balance_interval(sd, 0); |
| next = sd->last_balance + interval; |
| |
| if (time_after(*next_balance, next)) |
| *next_balance = next; |
| } |
| |
| /* |
| * active_load_balance_cpu_stop is run by the CPU stopper. It pushes |
| * running tasks off the busiest CPU onto idle CPUs. It requires at |
| * least 1 task to be running on each physical CPU where possible, and |
| * avoids physical / logical imbalances. |
| */ |
| static int active_load_balance_cpu_stop(void *data) |
| { |
| struct rq *busiest_rq = data; |
| int busiest_cpu = cpu_of(busiest_rq); |
| int target_cpu = busiest_rq->push_cpu; |
| struct rq *target_rq = cpu_rq(target_cpu); |
| struct sched_domain *sd; |
| struct task_struct *p = NULL; |
| struct rq_flags rf; |
| |
| rq_lock_irq(busiest_rq, &rf); |
| /* |
| * Between queueing the stop-work and running it is a hole in which |
| * CPUs can become inactive. We should not move tasks from or to |
| * inactive CPUs. |
| */ |
| if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu)) |
| goto out_unlock; |
| |
| /* Make sure the requested CPU hasn't gone down in the meantime: */ |
| if (unlikely(busiest_cpu != smp_processor_id() || |
| !busiest_rq->active_balance)) |
| goto out_unlock; |
| |
| /* Is there any task to move? */ |
| if (busiest_rq->nr_running <= 1) |
| goto out_unlock; |
| |
| /* |
| * This condition is "impossible", if it occurs |
| * we need to fix it. Originally reported by |
| * Bjorn Helgaas on a 128-CPU setup. |
| */ |
| BUG_ON(busiest_rq == target_rq); |
| |
| /* Search for an sd spanning us and the target CPU. */ |
| rcu_read_lock(); |
| for_each_domain(target_cpu, sd) { |
| if ((sd->flags & SD_LOAD_BALANCE) && |
| cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) |
| break; |
| } |
| |
| if (likely(sd)) { |
| struct lb_env env = { |
| .sd = sd, |
| .dst_cpu = target_cpu, |
| .dst_rq = target_rq, |
| .src_cpu = busiest_rq->cpu, |
| .src_rq = busiest_rq, |
| .idle = CPU_IDLE, |
| /* |
| * can_migrate_task() doesn't need to compute new_dst_cpu |
| * for active balancing. Since we have CPU_IDLE, but no |
| * @dst_grpmask we need to make that test go away with lying |
| * about DST_PINNED. |
| */ |
| .flags = LBF_DST_PINNED, |
| }; |
| |
| schedstat_inc(sd->alb_count); |
| update_rq_clock(busiest_rq); |
| |
| p = detach_one_task(&env); |
| if (p) { |
| schedstat_inc(sd->alb_pushed); |
| /* Active balancing done, reset the failure counter. */ |
| sd->nr_balance_failed = 0; |
| } else { |
| schedstat_inc(sd->alb_failed); |
| } |
| } |
| rcu_read_unlock(); |
| out_unlock: |
| busiest_rq->active_balance = 0; |
| rq_unlock(busiest_rq, &rf); |
| |
| if (p) |
| attach_one_task(target_rq, p); |
| |
| local_irq_enable(); |
| |
| return 0; |
| } |
| |
| static DEFINE_SPINLOCK(balancing); |
| |
| /* |
| * Scale the max load_balance interval with the number of CPUs in the system. |
| * This trades load-balance latency on larger machines for less cross talk. |
| */ |
| void update_max_interval(void) |
| { |
| max_load_balance_interval = HZ*num_online_cpus()/10; |
| } |
| |
| /* |
| * It checks each scheduling domain to see if it is due to be balanced, |
| * and initiates a balancing operation if so. |
| * |
| * Balancing parameters are set up in init_sched_domains. |
| */ |
| static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) |
| { |
| int continue_balancing = 1; |
| int cpu = rq->cpu; |
| int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu); |
| unsigned long interval; |
| struct sched_domain *sd; |
| /* Earliest time when we have to do rebalance again */ |
| unsigned long next_balance = jiffies + 60*HZ; |
| int update_next_balance = 0; |
| int need_serialize, need_decay = 0; |
| u64 max_cost = 0; |
| |
| rcu_read_lock(); |
| for_each_domain(cpu, sd) { |
| /* |
| * Decay the newidle max times here because this is a regular |
| * visit to all the domains. Decay ~1% per second. |
| */ |
| if (time_after(jiffies, sd->next_decay_max_lb_cost)) { |
| sd->max_newidle_lb_cost = |
| (sd->max_newidle_lb_cost * 253) / 256; |
| sd->next_decay_max_lb_cost = jiffies + HZ; |
| need_decay = 1; |
| } |
| max_cost += sd->max_newidle_lb_cost; |
| |
| if (!(sd->flags & SD_LOAD_BALANCE)) |
| continue; |
| |
| /* |
| * Stop the load balance at this level. There is another |
| * CPU in our sched group which is doing load balancing more |
| * actively. |
| */ |
| if (!continue_balancing) { |
| if (need_decay) |
| continue; |
| break; |
| } |
| |
| interval = get_sd_balance_interval(sd, busy); |
| |
| need_serialize = sd->flags & SD_SERIALIZE; |
| if (need_serialize) { |
| if (!spin_trylock(&balancing)) |
| goto out; |
| } |
| |
| if (time_after_eq(jiffies, sd->last_balance + interval)) { |
| if (load_balance(cpu, rq, sd, idle, &continue_balancing)) { |
| /* |
| * The LBF_DST_PINNED logic could have changed |
| * env->dst_cpu, so we can't know our idle |
| * state even if we migrated tasks. Update it. |
| */ |
| idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; |
| busy = idle != CPU_IDLE && !sched_idle_cpu(cpu); |
| } |
| sd->last_balance = jiffies; |
| interval = get_sd_balance_interval(sd, busy); |
| } |
| if (need_serialize) |
| spin_unlock(&balancing); |
| out: |
| if (time_after(next_balance, sd->last_balance + interval)) { |
| next_balance = sd->last_balance + interval; |
| update_next_balance = 1; |
| } |
| } |
| if (need_decay) { |
| /* |
| * Ensure the rq-wide value also decays but keep it at a |
| * reasonable floor to avoid funnies with rq->avg_idle. |
| */ |
| rq->max_idle_balance_cost = |
| max((u64)sysctl_sched_migration_cost, max_cost); |
| } |
| rcu_read_unlock(); |
| |
| /* |
| * next_balance will be updated only when there is a need. |
| * When the cpu is attached to null domain for ex, it will not be |
| * updated. |
| */ |
| if (likely(update_next_balance)) { |
| rq->next_balance = next_balance; |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| /* |
| * If this CPU has been elected to perform the nohz idle |
| * balance. Other idle CPUs have already rebalanced with |
| * nohz_idle_balance() and nohz.next_balance has been |
| * updated accordingly. This CPU is now running the idle load |
| * balance for itself and we need to update the |
| * nohz.next_balance accordingly. |
| */ |
| if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance)) |
| nohz.next_balance = rq->next_balance; |
| #endif |
| } |
| } |
| |
| static inline int on_null_domain(struct rq *rq) |
| { |
| return unlikely(!rcu_dereference_sched(rq->sd)); |
| } |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| /* |
| * idle load balancing details |
| * - When one of the busy CPUs notice that there may be an idle rebalancing |
| * needed, they will kick the idle load balancer, which then does idle |
| * load balancing for all the idle CPUs. |
| * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set |
| * anywhere yet. |
| */ |
| |
| static inline int find_new_ilb(void) |
| { |
| int ilb; |
| |
| for_each_cpu_and(ilb, nohz.idle_cpus_mask, |
| housekeeping_cpumask(HK_FLAG_MISC)) { |
| if (idle_cpu(ilb)) |
| return ilb; |
| } |
| |
| return nr_cpu_ids; |
| } |
| |
| /* |
| * Kick a CPU to do the nohz balancing, if it is time for it. We pick any |
| * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one). |
| */ |
| static void kick_ilb(unsigned int flags) |
| { |
| int ilb_cpu; |
| |
| nohz.next_balance++; |
| |
| ilb_cpu = find_new_ilb(); |
| |
| if (ilb_cpu >= nr_cpu_ids) |
| return; |
| |
| flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu)); |
| if (flags & NOHZ_KICK_MASK) |
| return; |
| |
| /* |
| * Use smp_send_reschedule() instead of resched_cpu(). |
| * This way we generate a sched IPI on the target CPU which |
| * is idle. And the softirq performing nohz idle load balance |
| * will be run before returning from the IPI. |
| */ |
| smp_send_reschedule(ilb_cpu); |
| } |
| |
| /* |
| * Current decision point for kicking the idle load balancer in the presence |
| * of idle CPUs in the system. |
| */ |
| static void nohz_balancer_kick(struct rq *rq) |
| { |
| unsigned long now = jiffies; |
| struct sched_domain_shared *sds; |
| struct sched_domain *sd; |
| int nr_busy, i, cpu = rq->cpu; |
| unsigned int flags = 0; |
| |
| if (unlikely(rq->idle_balance)) |
| return; |
| |
| /* |
| * We may be recently in ticked or tickless idle mode. At the first |
| * busy tick after returning from idle, we will update the busy stats. |
| */ |
| nohz_balance_exit_idle(rq); |
| |
| /* |
| * None are in tickless mode and hence no need for NOHZ idle load |
| * balancing. |
| */ |
| if (likely(!atomic_read(&nohz.nr_cpus))) |
| return; |
| |
| if (READ_ONCE(nohz.has_blocked) && |
| time_after(now, READ_ONCE(nohz.next_blocked))) |
| flags = NOHZ_STATS_KICK; |
| |
| if (time_before(now, nohz.next_balance)) |
| goto out; |
| |
| if (rq->nr_running >= 2) { |
| flags = NOHZ_KICK_MASK; |
| goto out; |
| } |
| |
| rcu_read_lock(); |
| |
| sd = rcu_dereference(rq->sd); |
| if (sd) { |
| /* |
| * If there's a CFS task and the current CPU has reduced |
| * capacity; kick the ILB to see if there's a better CPU to run |
| * on. |
| */ |
| if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) { |
| flags = NOHZ_KICK_MASK; |
| goto unlock; |
| } |
| } |
| |
| sd = rcu_dereference(per_cpu(sd_asym_packing, cpu)); |
| if (sd) { |
| /* |
| * When ASYM_PACKING; see if there's a more preferred CPU |
| * currently idle; in which case, kick the ILB to move tasks |
| * around. |
| */ |
| for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) { |
| if (sched_asym_prefer(i, cpu)) { |
| flags = NOHZ_KICK_MASK; |
| goto unlock; |
| } |
| } |
| } |
| |
| sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu)); |
| if (sd) { |
| /* |
| * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU |
| * to run the misfit task on. |
| */ |
| if (check_misfit_status(rq, sd)) { |
| flags = NOHZ_KICK_MASK; |
| goto unlock; |
| } |
| |
| /* |
| * For asymmetric systems, we do not want to nicely balance |
| * cache use, instead we want to embrace asymmetry and only |
| * ensure tasks have enough CPU capacity. |
| * |
| * Skip the LLC logic because it's not relevant in that case. |
| */ |
| goto unlock; |
| } |
| |
| sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); |
| if (sds) { |
| /* |
| * If there is an imbalance between LLC domains (IOW we could |
| * increase the overall cache use), we need some less-loaded LLC |
| * domain to pull some load. Likewise, we may need to spread |
| * load within the current LLC domain (e.g. packed SMT cores but |
| * other CPUs are idle). We can't really know from here how busy |
| * the others are - so just get a nohz balance going if it looks |
| * like this LLC domain has tasks we could move. |
| */ |
| nr_busy = atomic_read(&sds->nr_busy_cpus); |
| if (nr_busy > 1) { |
| flags = NOHZ_KICK_MASK; |
| goto unlock; |
| } |
| } |
| unlock: |
| rcu_read_unlock(); |
| out: |
| if (flags) |
| kick_ilb(flags); |
| } |
| |
| static void set_cpu_sd_state_busy(int cpu) |
| { |
| struct sched_domain *sd; |
| |
| rcu_read_lock(); |
| sd = rcu_dereference(per_cpu(sd_llc, cpu)); |
| |
| if (!sd || !sd->nohz_idle) |
| goto unlock; |
| sd->nohz_idle = 0; |
| |
| atomic_inc(&sd->shared->nr_busy_cpus); |
| unlock: |
| rcu_read_unlock(); |
| } |
| |
| void nohz_balance_exit_idle(struct rq *rq) |
| { |
| SCHED_WARN_ON(rq != this_rq()); |
| |
| if (likely(!rq->nohz_tick_stopped)) |
| return; |
| |
| rq->nohz_tick_stopped = 0; |
| cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask); |
| atomic_dec(&nohz.nr_cpus); |
| |
| set_cpu_sd_state_busy(rq->cpu); |
| } |
| |
| static void set_cpu_sd_state_idle(int cpu) |
| { |
| struct sched_domain *sd; |
| |
| rcu_read_lock(); |
| sd = rcu_dereference(per_cpu(sd_llc, cpu)); |
| |
| if (!sd || sd->nohz_idle) |
| goto unlock; |
| sd->nohz_idle = 1; |
| |
| atomic_dec(&sd->shared->nr_busy_cpus); |
| unlock: |
| rcu_read_unlock(); |
| } |
| |
| /* |
| * This routine will record that the CPU is going idle with tick stopped. |
| * This info will be used in performing idle load balancing in the future. |
| */ |
| void nohz_balance_enter_idle(int cpu) |
| { |
| struct rq *rq = cpu_rq(cpu); |
| |
| SCHED_WARN_ON(cpu != smp_processor_id()); |
| |
| /* If this CPU is going down, then nothing needs to be done: */ |
| if (!cpu_active(cpu)) |
| return; |
| |
| /* Spare idle load balancing on CPUs that don't want to be disturbed: */ |
| if (!housekeeping_cpu(cpu, HK_FLAG_SCHED)) |
| return; |
| |
| /* |
| * Can be set safely without rq->lock held |
| * If a clear happens, it will have evaluated last additions because |
| * rq->lock is held during the check and the clear |
| */ |
| rq->has_blocked_load = 1; |
| |
| /* |
| * The tick is still stopped but load could have been added in the |
| * meantime. We set the nohz.has_blocked flag to trig a check of the |
| * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear |
| * of nohz.has_blocked can only happen after checking the new load |
| */ |
| if (rq->nohz_tick_stopped) |
| goto out; |
| |
| /* If we're a completely isolated CPU, we don't play: */ |
| if (on_null_domain(rq)) |
| return; |
| |
| rq->nohz_tick_stopped = 1; |
| |
| cpumask_set_cpu(cpu, nohz.idle_cpus_mask); |
| atomic_inc(&nohz.nr_cpus); |
| |
| /* |
| * Ensures that if nohz_idle_balance() fails to observe our |
| * @idle_cpus_mask store, it must observe the @has_blocked |
| * store. |
| */ |
| smp_mb__after_atomic(); |
| |
| set_cpu_sd_state_idle(cpu); |
| |
| out: |
| /* |
| * Each time a cpu enter idle, we assume that it has blocked load and |
| * enable the periodic update of the load of idle cpus |
| */ |
| WRITE_ONCE(nohz.has_blocked, 1); |
| } |
| |
| /* |
| * Internal function that runs load balance for all idle cpus. The load balance |
| * can be a simple update of blocked load or a complete load balance with |
| * tasks movement depending of flags. |
| * The function returns false if the loop has stopped before running |
| * through all idle CPUs. |
| */ |
| static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags, |
| enum cpu_idle_type idle) |
| { |
| /* Earliest time when we have to do rebalance again */ |
| unsigned long now = jiffies; |
| unsigned long next_balance = now + 60*HZ; |
| bool has_blocked_load = false; |
| int update_next_balance = 0; |
| int this_cpu = this_rq->cpu; |
| int balance_cpu; |
| int ret = false; |
| struct rq *rq; |
| |
| SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK); |
| |
| /* |
| * We assume there will be no idle load after this update and clear |
| * the has_blocked flag. If a cpu enters idle in the mean time, it will |
| * set the has_blocked flag and trig another update of idle load. |
| * Because a cpu that becomes idle, is added to idle_cpus_mask before |
| * setting the flag, we are sure to not clear the state and not |
| * check the load of an idle cpu. |
| */ |
| WRITE_ONCE(nohz.has_blocked, 0); |
| |
| /* |
| * Ensures that if we miss the CPU, we must see the has_blocked |
| * store from nohz_balance_enter_idle(). |
| */ |
| smp_mb(); |
| |
| for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { |
| if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) |
| continue; |
| |
| /* |
| * If this CPU gets work to do, stop the load balancing |
| * work being done for other CPUs. Next load |
| * balancing owner will pick it up. |
| */ |
| if (need_resched()) { |
| has_blocked_load = true; |
| goto abort; |
| } |
| |
| rq = cpu_rq(balance_cpu); |
| |
| has_blocked_load |= update_nohz_stats(rq, true); |
| |
| /* |
| * If time for next balance is due, |
| * do the balance. |
| */ |
| if (time_after_eq(jiffies, rq->next_balance)) { |
| struct rq_flags rf; |
| |
| rq_lock_irqsave(rq, &rf); |
| update_rq_clock(rq); |
| rq_unlock_irqrestore(rq, &rf); |
| |
| if (flags & NOHZ_BALANCE_KICK) |
| rebalance_domains(rq, CPU_IDLE); |
| } |
| |
| if (time_after(next_balance, rq->next_balance)) { |
| next_balance = rq->next_balance; |
| update_next_balance = 1; |
| } |
| } |
| |
| /* Newly idle CPU doesn't need an update */ |
| if (idle != CPU_NEWLY_IDLE) { |
| update_blocked_averages(this_cpu); |
| has_blocked_load |= this_rq->has_blocked_load; |
| } |
| |
| if (flags & NOHZ_BALANCE_KICK) |
| rebalance_domains(this_rq, CPU_IDLE); |
| |
| WRITE_ONCE(nohz.next_blocked, |
| now + msecs_to_jiffies(LOAD_AVG_PERIOD)); |
| |
| /* The full idle balance loop has been done */ |
| ret = true; |
| |
| abort: |
| /* There is still blocked load, enable periodic update */ |
| if (has_blocked_load) |
| WRITE_ONCE(nohz.has_blocked, 1); |
| |
| /* |
| * next_balance will be updated only when there is a need. |
| * When the CPU is attached to null domain for ex, it will not be |
| * updated. |
| */ |
| if (likely(update_next_balance)) |
| nohz.next_balance = next_balance; |
| |
| return ret; |
| } |
| |
| /* |
| * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the |
| * rebalancing for all the cpus for whom scheduler ticks are stopped. |
| */ |
| static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) |
| { |
| int this_cpu = this_rq->cpu; |
| unsigned int flags; |
| |
| if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK)) |
| return false; |
| |
| if (idle != CPU_IDLE) { |
| atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu)); |
| return false; |
| } |
| |
| /* could be _relaxed() */ |
| flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu)); |
| if (!(flags & NOHZ_KICK_MASK)) |
| return false; |
| |
| _nohz_idle_balance(this_rq, flags, idle); |
| |
| return true; |
| } |
| |
| static void nohz_newidle_balance(struct rq *this_rq) |
| { |
| int this_cpu = this_rq->cpu; |
| |
| /* |
| * This CPU doesn't want to be disturbed by scheduler |
| * housekeeping |
| */ |
| if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED)) |
| return; |
| |
| /* Will wake up very soon. No time for doing anything else*/ |
| if (this_rq->avg_idle < sysctl_sched_migration_cost) |
| return; |
| |
| /* Don't need to update blocked load of idle CPUs*/ |
| if (!READ_ONCE(nohz.has_blocked) || |
| time_before(jiffies, READ_ONCE(nohz.next_blocked))) |
| return; |
| |
| raw_spin_unlock(&this_rq->lock); |
| /* |
| * This CPU is going to be idle and blocked load of idle CPUs |
| * need to be updated. Run the ilb locally as it is a good |
| * candidate for ilb instead of waking up another idle CPU. |
| * Kick an normal ilb if we failed to do the update. |
| */ |
| if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE)) |
| kick_ilb(NOHZ_STATS_KICK); |
| raw_spin_lock(&this_rq->lock); |
| } |
| |
| #else /* !CONFIG_NO_HZ_COMMON */ |
| static inline void nohz_balancer_kick(struct rq *rq) { } |
| |
| static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) |
| { |
| return false; |
| } |
| |
| static inline void nohz_newidle_balance(struct rq *this_rq) { } |
| #endif /* CONFIG_NO_HZ_COMMON */ |
| |
| /* |
| * idle_balance is called by schedule() if this_cpu is about to become |
| * idle. Attempts to pull tasks from other CPUs. |
| * |
| * Returns: |
| * < 0 - we released the lock and there are !fair tasks present |
| * 0 - failed, no new tasks |
| * > 0 - success, new (fair) tasks present |
| */ |
| int newidle_balance(struct rq *this_rq, struct rq_flags *rf) |
| { |
| unsigned long next_balance = jiffies + HZ; |
| int this_cpu = this_rq->cpu; |
| struct sched_domain *sd; |
| int pulled_task = 0; |
| u64 curr_cost = 0; |
| |
| update_misfit_status(NULL, this_rq); |
| /* |
| * We must set idle_stamp _before_ calling idle_balance(), such that we |
| * measure the duration of idle_balance() as idle time. |
| */ |
| this_rq->idle_stamp = rq_clock(this_rq); |
| |
| /* |
| * Do not pull tasks towards !active CPUs... |
| */ |
| if (!cpu_active(this_cpu)) |
| return 0; |
| |
| /* |
| * This is OK, because current is on_cpu, which avoids it being picked |
| * for load-balance and preemption/IRQs are still disabled avoiding |
| * further scheduler activity on it and we're being very careful to |
| * re-start the picking loop. |
| */ |
| rq_unpin_lock(this_rq, rf); |
| |
| if (this_rq->avg_idle < sysctl_sched_migration_cost || |
| !READ_ONCE(this_rq->rd->overload)) { |
| |
| rcu_read_lock(); |
| sd = rcu_dereference_check_sched_domain(this_rq->sd); |
| if (sd) |
| update_next_balance(sd, &next_balance); |
| rcu_read_unlock(); |
| |
| nohz_newidle_balance(this_rq); |
| |
| goto out; |
| } |
| |
| raw_spin_unlock(&this_rq->lock); |
| |
| update_blocked_averages(this_cpu); |
| rcu_read_lock(); |
| for_each_domain(this_cpu, sd) { |
| int continue_balancing = 1; |
| u64 t0, domain_cost; |
| |
| if (!(sd->flags & SD_LOAD_BALANCE)) |
| continue; |
| |
| if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) { |
| update_next_balance(sd, &next_balance); |
| break; |
| } |
| |
| if (sd->flags & SD_BALANCE_NEWIDLE) { |
| t0 = sched_clock_cpu(this_cpu); |
| |
| pulled_task = load_balance(this_cpu, this_rq, |
| sd, CPU_NEWLY_IDLE, |
| &continue_balancing); |
| |
| domain_cost = sched_clock_cpu(this_cpu) - t0; |
| if (domain_cost > sd->max_newidle_lb_cost) |
| sd->max_newidle_lb_cost = domain_cost; |
| |
| curr_cost += domain_cost; |
| } |
| |
| update_next_balance(sd, &next_balance); |
| |
| /* |
| * Stop searching for tasks to pull if there are |
| * now runnable tasks on this rq. |
| */ |
| if (pulled_task || this_rq->nr_running > 0) |
| break; |
| } |
| rcu_read_unlock(); |
| |
| raw_spin_lock(&this_rq->lock); |
| |
| if (curr_cost > this_rq->max_idle_balance_cost) |
| this_rq->max_idle_balance_cost = curr_cost; |
| |
| out: |
| /* |
| * While browsing the domains, we released the rq lock, a task could |
| * have been enqueued in the meantime. Since we're not going idle, |
| * pretend we pulled a task. |
| */ |
| if (this_rq->cfs.h_nr_running && !pulled_task) |
| pulled_task = 1; |
| |
| /* Move the next balance forward */ |
| if (time_after(this_rq->next_balance, next_balance)) |
| this_rq->next_balance = next_balance; |
| |
| /* Is there a task of a high priority class? */ |
| if (this_rq->nr_running != this_rq->cfs.h_nr_running) |
| pulled_task = -1; |
| |
| if (pulled_task) |
| this_rq->idle_stamp = 0; |
| |
| rq_repin_lock(this_rq, rf); |
| |
| return pulled_task; |
| } |
| |
| /* |
| * run_rebalance_domains is triggered when needed from the scheduler tick. |
| * Also triggered for nohz idle balancing (with nohz_balancing_kick set). |
| */ |
| static __latent_entropy void run_rebalance_domains(struct softirq_action *h) |
| { |
| struct rq *this_rq = this_rq(); |
| enum cpu_idle_type idle = this_rq->idle_balance ? |
| CPU_IDLE : CPU_NOT_IDLE; |
| |
| /* |
| * If this CPU has a pending nohz_balance_kick, then do the |
| * balancing on behalf of the other idle CPUs whose ticks are |
| * stopped. Do nohz_idle_balance *before* rebalance_domains to |
| * give the idle CPUs a chance to load balance. Else we may |
| * load balance only within the local sched_domain hierarchy |
| * and abort nohz_idle_balance altogether if we pull some load. |
| */ |
| if (nohz_idle_balance(this_rq, idle)) |
| return; |
| |
| /* normal load balance */ |
| update_blocked_averages(this_rq->cpu); |
| rebalance_domains(this_rq, idle); |
| } |
| |
| /* |
| * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. |
| */ |
| void trigger_load_balance(struct rq *rq) |
| { |
| /* Don't need to rebalance while attached to NULL domain */ |
| if (unlikely(on_null_domain(rq))) |
| return; |
| |
| if (time_after_eq(jiffies, rq->next_balance)) |
| raise_softirq(SCHED_SOFTIRQ); |
| |
| nohz_balancer_kick(rq); |
| } |
| |
| static void rq_online_fair(struct rq *rq) |
| { |
| update_sysctl(); |
| |
| update_runtime_enabled(rq); |
| } |
| |
| static void rq_offline_fair(struct rq *rq) |
| { |
| update_sysctl(); |
| |
| /* Ensure any throttled groups are reachable by pick_next_task */ |
| unthrottle_offline_cfs_rqs(rq); |
| } |
| |
| #endif /* CONFIG_SMP */ |
| |
| /* |
| * scheduler tick hitting a task of our scheduling class. |
| * |
| * NOTE: This function can be called remotely by the tick offload that |
| * goes along full dynticks. Therefore no local assumption can be made |
| * and everything must be accessed through the @rq and @curr passed in |
| * parameters. |
| */ |
| static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) |
| { |
| struct cfs_rq *cfs_rq; |
| struct sched_entity *se = &curr->se; |
| |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| entity_tick(cfs_rq, se, queued); |
| } |
| |
| if (static_branch_unlikely(&sched_numa_balancing)) |
| task_tick_numa(rq, curr); |
| |
| update_misfit_status(curr, rq); |
| update_overutilized_status(task_rq(curr)); |
| } |
| |
| /* |
| * called on fork with the child task as argument from the parent's context |
| * - child not yet on the tasklist |
| * - preemption disabled |
| */ |
| static void task_fork_fair(struct task_struct *p) |
| { |
| struct cfs_rq *cfs_rq; |
| struct sched_entity *se = &p->se, *curr; |
| struct rq *rq = this_rq(); |
| struct rq_flags rf; |
| |
| rq_lock(rq, &rf); |
| update_rq_clock(rq); |
| |
| cfs_rq = task_cfs_rq(current); |
| curr = cfs_rq->curr; |
| if (curr) { |
| update_curr(cfs_rq); |
| se->vruntime = curr->vruntime; |
| } |
| place_entity(cfs_rq, se, 1); |
| |
| if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { |
| /* |
| * Upon rescheduling, sched_class::put_prev_task() will place |
| * 'current' within the tree based on its new key value. |
| */ |
| swap(curr->vruntime, se->vruntime); |
| resched_curr(rq); |
| } |
| |
| se->vruntime -= cfs_rq->min_vruntime; |
| rq_unlock(rq, &rf); |
| } |
| |
| /* |
| * Priority of the task has changed. Check to see if we preempt |
| * the current task. |
| */ |
| static void |
| prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) |
| { |
| if (!task_on_rq_queued(p)) |
| return; |
| |
| if (rq->cfs.nr_running == 1) |
| return; |
| |
| /* |
| * Reschedule if we are currently running on this runqueue and |
| * our priority decreased, or if we are not currently running on |
| * this runqueue and our priority is higher than the current's |
| */ |
| if (rq->curr == p) { |
| if (p->prio > oldprio) |
| resched_curr(rq); |
| } else |
| check_preempt_curr(rq, p, 0); |
| } |
| |
| static inline bool vruntime_normalized(struct task_struct *p) |
| { |
| struct sched_entity *se = &p->se; |
| |
| /* |
| * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases, |
| * the dequeue_entity(.flags=0) will already have normalized the |
| * vruntime. |
| */ |
| if (p->on_rq) |
| return true; |
| |
| /* |
| * When !on_rq, vruntime of the task has usually NOT been normalized. |
| * But there are some cases where it has already been normalized: |
| * |
| * - A forked child which is waiting for being woken up by |
| * wake_up_new_task(). |
| * - A task which has been woken up by try_to_wake_up() and |
| * waiting for actually being woken up by sched_ttwu_pending(). |
| */ |
| if (!se->sum_exec_runtime || |
| (p->state == TASK_WAKING && p->sched_remote_wakeup)) |
| return true; |
| |
| return false; |
| } |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| /* |
| * Propagate the changes of the sched_entity across the tg tree to make it |
| * visible to the root |
| */ |
| static void propagate_entity_cfs_rq(struct sched_entity *se) |
| { |
| struct cfs_rq *cfs_rq; |
| |
| /* Start to propagate at parent */ |
| se = se->parent; |
| |
| for_each_sched_entity(se) { |
| cfs_rq = cfs_rq_of(se); |
| |
| if (cfs_rq_throttled(cfs_rq)) |
| break; |
| |
| update_load_avg(cfs_rq, se, UPDATE_TG); |
| } |
| } |
| #else |
| static void propagate_entity_cfs_rq(struct sched_entity *se) { } |
| #endif |
| |
| static void detach_entity_cfs_rq(struct sched_entity *se) |
| { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| |
| /* Catch up with the cfs_rq and remove our load when we leave */ |
| update_load_avg(cfs_rq, se, 0); |
| detach_entity_load_avg(cfs_rq, se); |
| update_tg_load_avg(cfs_rq, false); |
| propagate_entity_cfs_rq(se); |
| } |
| |
| static void attach_entity_cfs_rq(struct sched_entity *se) |
| { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| /* |
| * Since the real-depth could have been changed (only FAIR |
| * class maintain depth value), reset depth properly. |
| */ |
| se->depth = se->parent ? se->parent->depth + 1 : 0; |
| #endif |
| |
| /* Synchronize entity with its cfs_rq */ |
| update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD); |
| attach_entity_load_avg(cfs_rq, se); |
| update_tg_load_avg(cfs_rq, false); |
| propagate_entity_cfs_rq(se); |
| } |
| |
| static void detach_task_cfs_rq(struct task_struct *p) |
| { |
| struct sched_entity *se = &p->se; |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| |
| if (!vruntime_normalized(p)) { |
| /* |
| * Fix up our vruntime so that the current sleep doesn't |
| * cause 'unlimited' sleep bonus. |
| */ |
| place_entity(cfs_rq, se, 0); |
| se->vruntime -= cfs_rq->min_vruntime; |
| } |
| |
| detach_entity_cfs_rq(se); |
| } |
| |
| static void attach_task_cfs_rq(struct task_struct *p) |
| { |
| struct sched_entity *se = &p->se; |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| |
| attach_entity_cfs_rq(se); |
| |
| if (!vruntime_normalized(p)) |
| se->vruntime += cfs_rq->min_vruntime; |
| } |
| |
| static void switched_from_fair(struct rq *rq, struct task_struct *p) |
| { |
| detach_task_cfs_rq(p); |
| } |
| |
| static void switched_to_fair(struct rq *rq, struct task_struct *p) |
| { |
| attach_task_cfs_rq(p); |
| |
| if (task_on_rq_queued(p)) { |
| /* |
| * We were most likely switched from sched_rt, so |
| * kick off the schedule if running, otherwise just see |
| * if we can still preempt the current task. |
| */ |
| if (rq->curr == p) |
| resched_curr(rq); |
| else |
| check_preempt_curr(rq, p, 0); |
| } |
| } |
| |
| /* Account for a task changing its policy or group. |
| * |
| * This routine is mostly called to set cfs_rq->curr field when a task |
| * migrates between groups/classes. |
| */ |
| static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) |
| { |
| struct sched_entity *se = &p->se; |
| |
| #ifdef CONFIG_SMP |
| if (task_on_rq_queued(p)) { |
| /* |
| * Move the next running task to the front of the list, so our |
| * cfs_tasks list becomes MRU one. |
| */ |
| list_move(&se->group_node, &rq->cfs_tasks); |
| } |
| #endif |
| |
| for_each_sched_entity(se) { |
| struct cfs_rq *cfs_rq = cfs_rq_of(se); |
| |
| set_next_entity(cfs_rq, se); |
| /* ensure bandwidth has been allocated on our new cfs_rq */ |
| account_cfs_rq_runtime(cfs_rq, 0); |
| } |
| } |
| |
| void init_cfs_rq(struct cfs_rq *cfs_rq) |
| { |
| cfs_rq->tasks_timeline = RB_ROOT_CACHED; |
| cfs_rq->min_vruntime = (u64)(-(1LL << 20)); |
| #ifndef CONFIG_64BIT |
| cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; |
| #endif |
| #ifdef CONFIG_SMP |
| raw_spin_lock_init(&cfs_rq->removed.lock); |
| #endif |
| } |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| static void task_set_group_fair(struct task_struct *p) |
| { |
| struct sched_entity *se = &p->se; |
| |
| set_task_rq(p, task_cpu(p)); |
| se->depth = se->parent ? se->parent->depth + 1 : 0; |
| } |
| |
| static void task_move_group_fair(struct task_struct *p) |
| { |
| detach_task_cfs_rq(p); |
| set_task_rq(p, task_cpu(p)); |
| |
| #ifdef CONFIG_SMP |
| /* Tell se's cfs_rq has been changed -- migrated */ |
| p->se.avg.last_update_time = 0; |
| #endif |
| attach_task_cfs_rq(p); |
| } |
| |
| static void task_change_group_fair(struct task_struct *p, int type) |
| { |
| switch (type) { |
| case TASK_SET_GROUP: |
| task_set_group_fair(p); |
| break; |
| |
| case TASK_MOVE_GROUP: |
| task_move_group_fair(p); |
| break; |
| } |
| } |
| |
| void free_fair_sched_group(struct task_group *tg) |
| { |
| int i; |
| |
| destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); |
| |
| for_each_possible_cpu(i) { |
| if (tg->cfs_rq) |
| kfree(tg->cfs_rq[i]); |
| if (tg->se) |
| kfree(tg->se[i]); |
| } |
| |
| kfree(tg->cfs_rq); |
| kfree(tg->se); |
| } |
| |
| int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) |
| { |
| struct sched_entity *se; |
| struct cfs_rq *cfs_rq; |
| int i; |
| |
| tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL); |
| if (!tg->cfs_rq) |
| goto err; |
| tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL); |
| if (!tg->se) |
| goto err; |
| |
| tg->shares = NICE_0_LOAD; |
| |
| init_cfs_bandwidth(tg_cfs_bandwidth(tg)); |
| |
| for_each_possible_cpu(i) { |
| cfs_rq = kzalloc_node(sizeof(struct cfs_rq), |
| GFP_KERNEL, cpu_to_node(i)); |
| if (!cfs_rq) |
| goto err; |
| |
| se = kzalloc_node(sizeof(struct sched_entity), |
| GFP_KERNEL, cpu_to_node(i)); |
| if (!se) |
| goto err_free_rq; |
| |
| init_cfs_rq(cfs_rq); |
| init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); |
| init_entity_runnable_average(se); |
| } |
| |
| return 1; |
| |
| err_free_rq: |
| kfree(cfs_rq); |
| err: |
| return 0; |
| } |
| |
| void online_fair_sched_group(struct task_group *tg) |
| { |
| struct sched_entity *se; |
| struct rq_flags rf; |
| struct rq *rq; |
| int i; |
| |
| for_each_possible_cpu(i) { |
| rq = cpu_rq(i); |
| se = tg->se[i]; |
| rq_lock_irq(rq, &rf); |
| update_rq_clock(rq); |
| attach_entity_cfs_rq(se); |
| sync_throttle(tg, i); |
| rq_unlock_irq(rq, &rf); |
| } |
| } |
| |
| void unregister_fair_sched_group(struct task_group *tg) |
| { |
| unsigned long flags; |
| struct rq *rq; |
| int cpu; |
| |
| for_each_possible_cpu(cpu) { |
| if (tg->se[cpu]) |
| remove_entity_load_avg(tg->se[cpu]); |
| |
| /* |
| * Only empty task groups can be destroyed; so we can speculatively |
| * check on_list without danger of it being re-added. |
| */ |
| if (!tg->cfs_rq[cpu]->on_list) |
| continue; |
| |
| rq = cpu_rq(cpu); |
| |
| raw_spin_lock_irqsave(&rq->lock, flags); |
| list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); |
| raw_spin_unlock_irqrestore(&rq->lock, flags); |
| } |
| } |
| |
| void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, |
| struct sched_entity *se, int cpu, |
| struct sched_entity *parent) |
| { |
| struct rq *rq = cpu_rq(cpu); |
| |
| cfs_rq->tg = tg; |
| cfs_rq->rq = rq; |
| init_cfs_rq_runtime(cfs_rq); |
| |
| tg->cfs_rq[cpu] = cfs_rq; |
| tg->se[cpu] = se; |
| |
| /* se could be NULL for root_task_group */ |
| if (!se) |
| return; |
| |
| if (!parent) { |
| se->cfs_rq = &rq->cfs; |
| se->depth = 0; |
| } else { |
| se->cfs_rq = parent->my_q; |
| se->depth = parent->depth + 1; |
| } |
| |
| se->my_q = cfs_rq; |
| /* guarantee group entities always have weight */ |
| update_load_set(&se->load, NICE_0_LOAD); |
| se->parent = parent; |
| } |
| |
| static DEFINE_MUTEX(shares_mutex); |
| |
| int sched_group_set_shares(struct task_group *tg, unsigned long shares) |
| { |
| int i; |
| |
| /* |
| * We can't change the weight of the root cgroup. |
| */ |
| if (!tg->se[0]) |
| return -EINVAL; |
| |
| shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); |
| |
| mutex_lock(&shares_mutex); |
| if (tg->shares == shares) |
| goto done; |
| |
| tg->shares = shares; |
| for_each_possible_cpu(i) { |
| struct rq *rq = cpu_rq(i); |
| struct sched_entity *se = tg->se[i]; |
| struct rq_flags rf; |
| |
| /* Propagate contribution to hierarchy */ |
| rq_lock_irqsave(rq, &rf); |
| update_rq_clock(rq); |
| for_each_sched_entity(se) { |
| update_load_avg(cfs_rq_of(se), se, UPDATE_TG); |
| update_cfs_group(se); |
| } |
| rq_unlock_irqrestore(rq, &rf); |
| } |
| |
| done: |
| mutex_unlock(&shares_mutex); |
| return 0; |
| } |
| #else /* CONFIG_FAIR_GROUP_SCHED */ |
| |
| void free_fair_sched_group(struct task_group *tg) { } |
| |
| int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) |
| { |
| return 1; |
| } |
| |
| void online_fair_sched_group(struct task_group *tg) { } |
| |
| void unregister_fair_sched_group(struct task_group *tg) { } |
| |
| #endif /* CONFIG_FAIR_GROUP_SCHED */ |
| |
| |
| static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) |
| { |
| struct sched_entity *se = &task->se; |
| unsigned int rr_interval = 0; |
| |
| /* |
| * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise |
| * idle runqueue: |
| */ |
| if (rq->cfs.load.weight) |
| rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); |
| |
| return rr_interval; |
| } |
| |
| /* |
| * All the scheduling class methods: |
| */ |
| const struct sched_class fair_sched_class = { |
| .next = &idle_sched_class, |
| .enqueue_task = enqueue_task_fair, |
| .dequeue_task = dequeue_task_fair, |
| .yield_task = yield_task_fair, |
| .yield_to_task = yield_to_task_fair, |
| |
| .check_preempt_curr = check_preempt_wakeup, |
| |
| .pick_next_task = __pick_next_task_fair, |
| .put_prev_task = put_prev_task_fair, |
| .set_next_task = set_next_task_fair, |
| |
| #ifdef CONFIG_SMP |
| .balance = balance_fair, |
| .select_task_rq = select_task_rq_fair, |
| .migrate_task_rq = migrate_task_rq_fair, |
| |
| .rq_online = rq_online_fair, |
| .rq_offline = rq_offline_fair, |
| |
| .task_dead = task_dead_fair, |
| .set_cpus_allowed = set_cpus_allowed_common, |
| #endif |
| |
| .task_tick = task_tick_fair, |
| .task_fork = task_fork_fair, |
| |
| .prio_changed = prio_changed_fair, |
| .switched_from = switched_from_fair, |
| .switched_to = switched_to_fair, |
| |
| .get_rr_interval = get_rr_interval_fair, |
| |
| .update_curr = update_curr_fair, |
| |
| #ifdef CONFIG_FAIR_GROUP_SCHED |
| .task_change_group = task_change_group_fair, |
| #endif |
| |
| #ifdef CONFIG_UCLAMP_TASK |
| .uclamp_enabled = 1, |
| #endif |
| }; |
| |
| #ifdef CONFIG_SCHED_DEBUG |
| void print_cfs_stats(struct seq_file *m, int cpu) |
| { |
| struct cfs_rq *cfs_rq, *pos; |
| |
| rcu_read_lock(); |
| for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos) |
| print_cfs_rq(m, cpu, cfs_rq); |
| rcu_read_unlock(); |
| } |
| |
| #ifdef CONFIG_NUMA_BALANCING |
| void show_numa_stats(struct task_struct *p, struct seq_file *m) |
| { |
| int node; |
| unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0; |
| struct numa_group *ng; |
| |
| rcu_read_lock(); |
| ng = rcu_dereference(p->numa_group); |
| for_each_online_node(node) { |
| if (p->numa_faults) { |
| tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)]; |
| tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)]; |
| } |
| if (ng) { |
| gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)], |
| gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)]; |
| } |
| print_numa_stats(m, node, tsf, tpf, gsf, gpf); |
| } |
| rcu_read_unlock(); |
| } |
| #endif /* CONFIG_NUMA_BALANCING */ |
| #endif /* CONFIG_SCHED_DEBUG */ |
| |
| __init void init_sched_fair_class(void) |
| { |
| #ifdef CONFIG_SMP |
| open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); |
| |
| #ifdef CONFIG_NO_HZ_COMMON |
| nohz.next_balance = jiffies; |
| nohz.next_blocked = jiffies; |
| zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); |
| #endif |
| #endif /* SMP */ |
| |
| } |
| |
| /* |
| * Helper functions to facilitate extracting info from tracepoints. |
| */ |
| |
| const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq) |
| { |
| #ifdef CONFIG_SMP |
| return cfs_rq ? &cfs_rq->avg : NULL; |
| #else |
| return NULL; |
| #endif |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg); |
| |
| char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len) |
| { |
| if (!cfs_rq) { |
| if (str) |
| strlcpy(str, "(null)", len); |
| else |
| return NULL; |
| } |
| |
| cfs_rq_tg_path(cfs_rq, str, len); |
| return str; |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path); |
| |
| int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq) |
| { |
| return cfs_rq ? cpu_of(rq_of(cfs_rq)) : -1; |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu); |
| |
| const struct sched_avg *sched_trace_rq_avg_rt(struct rq *rq) |
| { |
| #ifdef CONFIG_SMP |
| return rq ? &rq->avg_rt : NULL; |
| #else |
| return NULL; |
| #endif |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt); |
| |
| const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq) |
| { |
| #ifdef CONFIG_SMP |
| return rq ? &rq->avg_dl : NULL; |
| #else |
| return NULL; |
| #endif |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl); |
| |
| const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq) |
| { |
| #if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ) |
| return rq ? &rq->avg_irq : NULL; |
| #else |
| return NULL; |
| #endif |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq); |
| |
| int sched_trace_rq_cpu(struct rq *rq) |
| { |
| return rq ? cpu_of(rq) : -1; |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_rq_cpu); |
| |
| const struct cpumask *sched_trace_rd_span(struct root_domain *rd) |
| { |
| #ifdef CONFIG_SMP |
| return rd ? rd->span : NULL; |
| #else |
| return NULL; |
| #endif |
| } |
| EXPORT_SYMBOL_GPL(sched_trace_rd_span); |