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android-kvm / linux / c853a5783ebe123847886d432354931874367292 / . / kernel / sched / topology.c
blob: b77ad49dc14f6a215c0b2df54703f17c8ed52b33 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Scheduler topology setup/handling methods
*/
#include "sched.h"
DEFINE_MUTEX(sched_domains_mutex);
/* Protected by sched_domains_mutex: */
static cpumask_var_t sched_domains_tmpmask;
static cpumask_var_t sched_domains_tmpmask2;
#ifdef CONFIG_SCHED_DEBUG
static int __init sched_debug_setup(char *str)
{
sched_debug_verbose = true;
return 0;
}
early_param("sched_verbose", sched_debug_setup);
static inline bool sched_debug(void)
{
return sched_debug_verbose;
}
#define SD_FLAG(_name, mflags) [__##_name] = { .meta_flags = mflags, .name = #_name },
const struct sd_flag_debug sd_flag_debug[] = {
#include <linux/sched/sd_flags.h>
};
#undef SD_FLAG
static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
struct cpumask *groupmask)
{
struct sched_group *group = sd->groups;
unsigned long flags = sd->flags;
unsigned int idx;
cpumask_clear(groupmask);
printk(KERN_DEBUG "%*s domain-%d: ", level, "", level);
printk(KERN_CONT "span=%*pbl level=%s\n",
cpumask_pr_args(sched_domain_span(sd)), sd->name);
if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
printk(KERN_ERR "ERROR: domain->span does not contain CPU%d\n", cpu);
}
if (group && !cpumask_test_cpu(cpu, sched_group_span(group))) {
printk(KERN_ERR "ERROR: domain->groups does not contain CPU%d\n", cpu);
}
for_each_set_bit(idx, &flags, __SD_FLAG_CNT) {
unsigned int flag = BIT(idx);
unsigned int meta_flags = sd_flag_debug[idx].meta_flags;
if ((meta_flags & SDF_SHARED_CHILD) && sd->child &&
!(sd->child->flags & flag))
printk(KERN_ERR "ERROR: flag %s set here but not in child\n",
sd_flag_debug[idx].name);
if ((meta_flags & SDF_SHARED_PARENT) && sd->parent &&
!(sd->parent->flags & flag))
printk(KERN_ERR "ERROR: flag %s set here but not in parent\n",
sd_flag_debug[idx].name);
}
printk(KERN_DEBUG "%*s groups:", level + 1, "");
do {
if (!group) {
printk("\n");
printk(KERN_ERR "ERROR: group is NULL\n");
break;
}
if (!cpumask_weight(sched_group_span(group))) {
printk(KERN_CONT "\n");
printk(KERN_ERR "ERROR: empty group\n");
break;
}
if (!(sd->flags & SD_OVERLAP) &&
cpumask_intersects(groupmask, sched_group_span(group))) {
printk(KERN_CONT "\n");
printk(KERN_ERR "ERROR: repeated CPUs\n");
break;
}
cpumask_or(groupmask, groupmask, sched_group_span(group));
printk(KERN_CONT " %d:{ span=%*pbl",
group->sgc->id,
cpumask_pr_args(sched_group_span(group)));
if ((sd->flags & SD_OVERLAP) &&
!cpumask_equal(group_balance_mask(group), sched_group_span(group))) {
printk(KERN_CONT " mask=%*pbl",
cpumask_pr_args(group_balance_mask(group)));
}
if (group->sgc->capacity != SCHED_CAPACITY_SCALE)
printk(KERN_CONT " cap=%lu", group->sgc->capacity);
if (group == sd->groups && sd->child &&
!cpumask_equal(sched_domain_span(sd->child),
sched_group_span(group))) {
printk(KERN_ERR "ERROR: domain->groups does not match domain->child\n");
}
printk(KERN_CONT " }");
group = group->next;
if (group != sd->groups)
printk(KERN_CONT ",");
} while (group != sd->groups);
printk(KERN_CONT "\n");
if (!cpumask_equal(sched_domain_span(sd), groupmask))
printk(KERN_ERR "ERROR: groups don't span domain->span\n");
if (sd->parent &&
!cpumask_subset(groupmask, sched_domain_span(sd->parent)))
printk(KERN_ERR "ERROR: parent span is not a superset of domain->span\n");
return 0;
}
static void sched_domain_debug(struct sched_domain *sd, int cpu)
{
int level = 0;
if (!sched_debug_verbose)
return;
if (!sd) {
printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
return;
}
printk(KERN_DEBUG "CPU%d attaching sched-domain(s):\n", cpu);
for (;;) {
if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
break;
level++;
sd = sd->parent;
if (!sd)
break;
}
}
#else /* !CONFIG_SCHED_DEBUG */
# define sched_debug_verbose 0
# define sched_domain_debug(sd, cpu) do { } while (0)
static inline bool sched_debug(void)
{
return false;
}
#endif /* CONFIG_SCHED_DEBUG */
/* Generate a mask of SD flags with the SDF_NEEDS_GROUPS metaflag */
#define SD_FLAG(name, mflags) (name * !!((mflags) & SDF_NEEDS_GROUPS)) |
static const unsigned int SD_DEGENERATE_GROUPS_MASK =
#include <linux/sched/sd_flags.h>
0;
#undef SD_FLAG
static int sd_degenerate(struct sched_domain *sd)
{
if (cpumask_weight(sched_domain_span(sd)) == 1)
return 1;
/* Following flags need at least 2 groups */
if ((sd->flags & SD_DEGENERATE_GROUPS_MASK) &&
(sd->groups != sd->groups->next))
return 0;
/* Following flags don't use groups */
if (sd->flags & (SD_WAKE_AFFINE))
return 0;
return 1;
}
static int
sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
{
unsigned long cflags = sd->flags, pflags = parent->flags;
if (sd_degenerate(parent))
return 1;
if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
return 0;
/* Flags needing groups don't count if only 1 group in parent */
if (parent->groups == parent->groups->next)
pflags &= ~SD_DEGENERATE_GROUPS_MASK;
if (~cflags & pflags)
return 0;
return 1;
}
#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
DEFINE_STATIC_KEY_FALSE(sched_energy_present);
unsigned int sysctl_sched_energy_aware = 1;
DEFINE_MUTEX(sched_energy_mutex);
bool sched_energy_update;
void rebuild_sched_domains_energy(void)
{
mutex_lock(&sched_energy_mutex);
sched_energy_update = true;
rebuild_sched_domains();
sched_energy_update = false;
mutex_unlock(&sched_energy_mutex);
}
#ifdef CONFIG_PROC_SYSCTL
int sched_energy_aware_handler(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
int ret, state;
if (write && !capable(CAP_SYS_ADMIN))
return -EPERM;
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!ret && write) {
state = static_branch_unlikely(&sched_energy_present);
if (state != sysctl_sched_energy_aware)
rebuild_sched_domains_energy();
}
return ret;
}
#endif
static void free_pd(struct perf_domain *pd)
{
struct perf_domain *tmp;
while (pd) {
tmp = pd->next;
kfree(pd);
pd = tmp;
}
}
static struct perf_domain *find_pd(struct perf_domain *pd, int cpu)
{
while (pd) {
if (cpumask_test_cpu(cpu, perf_domain_span(pd)))
return pd;
pd = pd->next;
}
return NULL;
}
static struct perf_domain *pd_init(int cpu)
{
struct em_perf_domain *obj = em_cpu_get(cpu);
struct perf_domain *pd;
if (!obj) {
if (sched_debug())
pr_info("%s: no EM found for CPU%d\n", __func__, cpu);
return NULL;
}
pd = kzalloc(sizeof(*pd), GFP_KERNEL);
if (!pd)
return NULL;
pd->em_pd = obj;
return pd;
}
static void perf_domain_debug(const struct cpumask *cpu_map,
struct perf_domain *pd)
{
if (!sched_debug() || !pd)
return;
printk(KERN_DEBUG "root_domain %*pbl:", cpumask_pr_args(cpu_map));
while (pd) {
printk(KERN_CONT " pd%d:{ cpus=%*pbl nr_pstate=%d }",
cpumask_first(perf_domain_span(pd)),
cpumask_pr_args(perf_domain_span(pd)),
em_pd_nr_perf_states(pd->em_pd));
pd = pd->next;
}
printk(KERN_CONT "\n");
}
static void destroy_perf_domain_rcu(struct rcu_head *rp)
{
struct perf_domain *pd;
pd = container_of(rp, struct perf_domain, rcu);
free_pd(pd);
}
static void sched_energy_set(bool has_eas)
{
if (!has_eas && static_branch_unlikely(&sched_energy_present)) {
if (sched_debug())
pr_info("%s: stopping EAS\n", __func__);
static_branch_disable_cpuslocked(&sched_energy_present);
} else if (has_eas && !static_branch_unlikely(&sched_energy_present)) {
if (sched_debug())
pr_info("%s: starting EAS\n", __func__);
static_branch_enable_cpuslocked(&sched_energy_present);
}
}
/*
* EAS can be used on a root domain if it meets all the following conditions:
* 1. an Energy Model (EM) is available;
* 2. the SD_ASYM_CPUCAPACITY flag is set in the sched_domain hierarchy.
* 3. no SMT is detected.
* 4. the EM complexity is low enough to keep scheduling overheads low;
* 5. schedutil is driving the frequency of all CPUs of the rd;
* 6. frequency invariance support is present;
*
* The complexity of the Energy Model is defined as:
*
* C = nr_pd * (nr_cpus + nr_ps)
*
* with parameters defined as:
* - nr_pd: the number of performance domains
* - nr_cpus: the number of CPUs
* - nr_ps: the sum of the number of performance states of all performance
* domains (for example, on a system with 2 performance domains,
* with 10 performance states each, nr_ps = 2 * 10 = 20).
*
* It is generally not a good idea to use such a model in the wake-up path on
* very complex platforms because of the associated scheduling overheads. The
* arbitrary constraint below prevents that. It makes EAS usable up to 16 CPUs
* with per-CPU DVFS and less than 8 performance states each, for example.
*/
#define EM_MAX_COMPLEXITY 2048
extern struct cpufreq_governor schedutil_gov;
static bool build_perf_domains(const struct cpumask *cpu_map)
{
int i, nr_pd = 0, nr_ps = 0, nr_cpus = cpumask_weight(cpu_map);
struct perf_domain *pd = NULL, *tmp;
int cpu = cpumask_first(cpu_map);
struct root_domain *rd = cpu_rq(cpu)->rd;
struct cpufreq_policy *policy;
struct cpufreq_governor *gov;
if (!sysctl_sched_energy_aware)
goto free;
/* EAS is enabled for asymmetric CPU capacity topologies. */
if (!per_cpu(sd_asym_cpucapacity, cpu)) {
if (sched_debug()) {
pr_info("rd %*pbl: CPUs do not have asymmetric capacities\n",
cpumask_pr_args(cpu_map));
}
goto free;
}
/* EAS definitely does *not* handle SMT */
if (sched_smt_active()) {
pr_warn("rd %*pbl: Disabling EAS, SMT is not supported\n",
cpumask_pr_args(cpu_map));
goto free;
}
if (!arch_scale_freq_invariant()) {
if (sched_debug()) {
pr_warn("rd %*pbl: Disabling EAS: frequency-invariant load tracking not yet supported",
cpumask_pr_args(cpu_map));
}
goto free;
}
for_each_cpu(i, cpu_map) {
/* Skip already covered CPUs. */
if (find_pd(pd, i))
continue;
/* Do not attempt EAS if schedutil is not being used. */
policy = cpufreq_cpu_get(i);
if (!policy)
goto free;
gov = policy->governor;
cpufreq_cpu_put(policy);
if (gov != &schedutil_gov) {
if (rd->pd)
pr_warn("rd %*pbl: Disabling EAS, schedutil is mandatory\n",
cpumask_pr_args(cpu_map));
goto free;
}
/* Create the new pd and add it to the local list. */
tmp = pd_init(i);
if (!tmp)
goto free;
tmp->next = pd;
pd = tmp;
/*
* Count performance domains and performance states for the
* complexity check.
*/
nr_pd++;
nr_ps += em_pd_nr_perf_states(pd->em_pd);
}
/* Bail out if the Energy Model complexity is too high. */
if (nr_pd * (nr_ps + nr_cpus) > EM_MAX_COMPLEXITY) {
WARN(1, "rd %*pbl: Failed to start EAS, EM complexity is too high\n",
cpumask_pr_args(cpu_map));
goto free;
}
perf_domain_debug(cpu_map, pd);
/* Attach the new list of performance domains to the root domain. */
tmp = rd->pd;
rcu_assign_pointer(rd->pd, pd);
if (tmp)
call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
return !!pd;
free:
free_pd(pd);
tmp = rd->pd;
rcu_assign_pointer(rd->pd, NULL);
if (tmp)
call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
return false;
}
#else
static void free_pd(struct perf_domain *pd) { }
#endif /* CONFIG_ENERGY_MODEL && CONFIG_CPU_FREQ_GOV_SCHEDUTIL*/
static void free_rootdomain(struct rcu_head *rcu)
{
struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
cpupri_cleanup(&rd->cpupri);
cpudl_cleanup(&rd->cpudl);
free_cpumask_var(rd->dlo_mask);
free_cpumask_var(rd->rto_mask);
free_cpumask_var(rd->online);
free_cpumask_var(rd->span);
free_pd(rd->pd);
kfree(rd);
}
void rq_attach_root(struct rq *rq, struct root_domain *rd)
{
struct root_domain *old_rd = NULL;
unsigned long flags;
raw_spin_rq_lock_irqsave(rq, flags);
if (rq->rd) {
old_rd = rq->rd;
if (cpumask_test_cpu(rq->cpu, old_rd->online))
set_rq_offline(rq);
cpumask_clear_cpu(rq->cpu, old_rd->span);
/*
* If we dont want to free the old_rd yet then
* set old_rd to NULL to skip the freeing later
* in this function:
*/
if (!atomic_dec_and_test(&old_rd->refcount))
old_rd = NULL;
}
atomic_inc(&rd->refcount);
rq->rd = rd;
cpumask_set_cpu(rq->cpu, rd->span);
if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
set_rq_online(rq);
raw_spin_rq_unlock_irqrestore(rq, flags);
if (old_rd)
call_rcu(&old_rd->rcu, free_rootdomain);
}
void sched_get_rd(struct root_domain *rd)
{
atomic_inc(&rd->refcount);
}
void sched_put_rd(struct root_domain *rd)
{
if (!atomic_dec_and_test(&rd->refcount))
return;
call_rcu(&rd->rcu, free_rootdomain);
}
static int init_rootdomain(struct root_domain *rd)
{
if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
goto out;
if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
goto free_span;
if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
goto free_online;
if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
goto free_dlo_mask;
#ifdef HAVE_RT_PUSH_IPI
rd->rto_cpu = -1;
raw_spin_lock_init(&rd->rto_lock);
init_irq_work(&rd->rto_push_work, rto_push_irq_work_func);
#endif
rd->visit_gen = 0;
init_dl_bw(&rd->dl_bw);
if (cpudl_init(&rd->cpudl) != 0)
goto free_rto_mask;
if (cpupri_init(&rd->cpupri) != 0)
goto free_cpudl;
return 0;
free_cpudl:
cpudl_cleanup(&rd->cpudl);
free_rto_mask:
free_cpumask_var(rd->rto_mask);
free_dlo_mask:
free_cpumask_var(rd->dlo_mask);
free_online:
free_cpumask_var(rd->online);
free_span:
free_cpumask_var(rd->span);
out:
return -ENOMEM;
}
/*
* By default the system creates a single root-domain with all CPUs as
* members (mimicking the global state we have today).
*/
struct root_domain def_root_domain;
void init_defrootdomain(void)
{
init_rootdomain(&def_root_domain);
atomic_set(&def_root_domain.refcount, 1);
}
static struct root_domain *alloc_rootdomain(void)
{
struct root_domain *rd;
rd = kzalloc(sizeof(*rd), GFP_KERNEL);
if (!rd)
return NULL;
if (init_rootdomain(rd) != 0) {
kfree(rd);
return NULL;
}
return rd;
}
static void free_sched_groups(struct sched_group *sg, int free_sgc)
{
struct sched_group *tmp, *first;
if (!sg)
return;
first = sg;
do {
tmp = sg->next;
if (free_sgc && atomic_dec_and_test(&sg->sgc->ref))
kfree(sg->sgc);
if (atomic_dec_and_test(&sg->ref))
kfree(sg);
sg = tmp;
} while (sg != first);
}
static void destroy_sched_domain(struct sched_domain *sd)
{
/*
* A normal sched domain may have multiple group references, an
* overlapping domain, having private groups, only one. Iterate,
* dropping group/capacity references, freeing where none remain.
*/
free_sched_groups(sd->groups, 1);
if (sd->shared && atomic_dec_and_test(&sd->shared->ref))
kfree(sd->shared);
kfree(sd);
}
static void destroy_sched_domains_rcu(struct rcu_head *rcu)
{
struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
while (sd) {
struct sched_domain *parent = sd->parent;
destroy_sched_domain(sd);
sd = parent;
}
}
static void destroy_sched_domains(struct sched_domain *sd)
{
if (sd)
call_rcu(&sd->rcu, destroy_sched_domains_rcu);
}
/*
* Keep a special pointer to the highest sched_domain that has
* SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
* allows us to avoid some pointer chasing select_idle_sibling().
*
* Also keep a unique ID per domain (we use the first CPU number in
* the cpumask of the domain), this allows us to quickly tell if
* two CPUs are in the same cache domain, see cpus_share_cache().
*/
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_llc);
DEFINE_PER_CPU(int, sd_llc_size);
DEFINE_PER_CPU(int, sd_llc_id);
DEFINE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);
static void update_top_cache_domain(int cpu)
{
struct sched_domain_shared *sds = NULL;
struct sched_domain *sd;
int id = cpu;
int size = 1;
sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
if (sd) {
id = cpumask_first(sched_domain_span(sd));
size = cpumask_weight(sched_domain_span(sd));
sds = sd->shared;
}
rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
per_cpu(sd_llc_size, cpu) = size;
per_cpu(sd_llc_id, cpu) = id;
rcu_assign_pointer(per_cpu(sd_llc_shared, cpu), sds);
sd = lowest_flag_domain(cpu, SD_NUMA);
rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
rcu_assign_pointer(per_cpu(sd_asym_packing, cpu), sd);
sd = lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY_FULL);
rcu_assign_pointer(per_cpu(sd_asym_cpucapacity, cpu), sd);
}
/*
* Attach the domain 'sd' to 'cpu' as its base domain. Callers must
* hold the hotplug lock.
*/
static void
cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
{
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
int numa_distance = 0;
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; ) {
struct sched_domain *parent = tmp->parent;
if (!parent)
break;
if (sd_parent_degenerate(tmp, parent)) {
tmp->parent = parent->parent;
if (parent->parent)
parent->parent->child = tmp;
/*
* Transfer SD_PREFER_SIBLING down in case of a
* degenerate parent; the spans match for this
* so the property transfers.
*/
if (parent->flags & SD_PREFER_SIBLING)
tmp->flags |= SD_PREFER_SIBLING;
destroy_sched_domain(parent);
} else
tmp = tmp->parent;
}
if (sd && sd_degenerate(sd)) {
tmp = sd;
sd = sd->parent;
destroy_sched_domain(tmp);
if (sd)
sd->child = NULL;
}
for (tmp = sd; tmp; tmp = tmp->parent)
numa_distance += !!(tmp->flags & SD_NUMA);
sched_domain_debug(sd, cpu);
rq_attach_root(rq, rd);
tmp = rq->sd;
rcu_assign_pointer(rq->sd, sd);
dirty_sched_domain_sysctl(cpu);
destroy_sched_domains(tmp);
update_top_cache_domain(cpu);
}
struct s_data {
struct sched_domain * __percpu *sd;
struct root_domain *rd;
};
enum s_alloc {
sa_rootdomain,
sa_sd,
sa_sd_storage,
sa_none,
};
/*
* Return the canonical balance CPU for this group, this is the first CPU
* of this group that's also in the balance mask.
*
* The balance mask are all those CPUs that could actually end up at this
* group. See build_balance_mask().
*
* Also see should_we_balance().
*/
int group_balance_cpu(struct sched_group *sg)
{
return cpumask_first(group_balance_mask(sg));
}
/*
* NUMA topology (first read the regular topology blurb below)
*
* Given a node-distance table, for example:
*
* node 0 1 2 3
* 0: 10 20 30 20
* 1: 20 10 20 30
* 2: 30 20 10 20
* 3: 20 30 20 10
*
* which represents a 4 node ring topology like:
*
* 0 ----- 1
* | |
* | |
* | |
* 3 ----- 2
*
* We want to construct domains and groups to represent this. The way we go
* about doing this is to build the domains on 'hops'. For each NUMA level we
* construct the mask of all nodes reachable in @level hops.
*
* For the above NUMA topology that gives 3 levels:
*
* NUMA-2 0-3 0-3 0-3 0-3
* groups: {0-1,3},{1-3} {0-2},{0,2-3} {1-3},{0-1,3} {0,2-3},{0-2}
*
* NUMA-1 0-1,3 0-2 1-3 0,2-3
* groups: {0},{1},{3} {0},{1},{2} {1},{2},{3} {0},{2},{3}
*
* NUMA-0 0 1 2 3
*
*
* As can be seen; things don't nicely line up as with the regular topology.
* When we iterate a domain in child domain chunks some nodes can be
* represented multiple times -- hence the "overlap" naming for this part of
* the topology.
*
* In order to minimize this overlap, we only build enough groups to cover the
* domain. For instance Node-0 NUMA-2 would only get groups: 0-1,3 and 1-3.
*
* Because:
*
* - the first group of each domain is its child domain; this
* gets us the first 0-1,3
* - the only uncovered node is 2, who's child domain is 1-3.
*
* However, because of the overlap, computing a unique CPU for each group is
* more complicated. Consider for instance the groups of NODE-1 NUMA-2, both
* groups include the CPUs of Node-0, while those CPUs would not in fact ever
* end up at those groups (they would end up in group: 0-1,3).
*
* To correct this we have to introduce the group balance mask. This mask
* will contain those CPUs in the group that can reach this group given the
* (child) domain tree.
*
* With this we can once again compute balance_cpu and sched_group_capacity
* relations.
*
* XXX include words on how balance_cpu is unique and therefore can be
* used for sched_group_capacity links.
*
*
* Another 'interesting' topology is:
*
* node 0 1 2 3
* 0: 10 20 20 30
* 1: 20 10 20 20
* 2: 20 20 10 20
* 3: 30 20 20 10
*
* Which looks a little like:
*
* 0 ----- 1
* | / |
* | / |
* | / |
* 2 ----- 3
*
* This topology is asymmetric, nodes 1,2 are fully connected, but nodes 0,3
* are not.
*
* This leads to a few particularly weird cases where the sched_domain's are
* not of the same number for each CPU. Consider:
*
* NUMA-2 0-3 0-3
* groups: {0-2},{1-3} {1-3},{0-2}
*
* NUMA-1 0-2 0-3 0-3 1-3
*
* NUMA-0 0 1 2 3
*
*/
/*
* Build the balance mask; it contains only those CPUs that can arrive at this
* group and should be considered to continue balancing.
*
* We do this during the group creation pass, therefore the group information
* isn't complete yet, however since each group represents a (child) domain we
* can fully construct this using the sched_domain bits (which are already
* complete).
*/
static void
build_balance_mask(struct sched_domain *sd, struct sched_group *sg, struct cpumask *mask)
{
const struct cpumask *sg_span = sched_group_span(sg);
struct sd_data *sdd = sd->private;
struct sched_domain *sibling;
int i;
cpumask_clear(mask);
for_each_cpu(i, sg_span) {
sibling = *per_cpu_ptr(sdd->sd, i);
/*
* Can happen in the asymmetric case, where these siblings are
* unused. The mask will not be empty because those CPUs that
* do have the top domain _should_ span the domain.
*/
if (!sibling->child)
continue;
/* If we would not end up here, we can't continue from here */
if (!cpumask_equal(sg_span, sched_domain_span(sibling->child)))
continue;
cpumask_set_cpu(i, mask);
}
/* We must not have empty masks here */
WARN_ON_ONCE(cpumask_empty(mask));
}
/*
* XXX: This creates per-node group entries; since the load-balancer will
* immediately access remote memory to construct this group's load-balance
* statistics having the groups node local is of dubious benefit.
*/
static struct sched_group *
build_group_from_child_sched_domain(struct sched_domain *sd, int cpu)
{
struct sched_group *sg;
struct cpumask *sg_span;
sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
GFP_KERNEL, cpu_to_node(cpu));
if (!sg)
return NULL;
sg_span = sched_group_span(sg);
if (sd->child)
cpumask_copy(sg_span, sched_domain_span(sd->child));
else
cpumask_copy(sg_span, sched_domain_span(sd));
atomic_inc(&sg->ref);
return sg;
}
static void init_overlap_sched_group(struct sched_domain *sd,
struct sched_group *sg)
{
struct cpumask *mask = sched_domains_tmpmask2;
struct sd_data *sdd = sd->private;
struct cpumask *sg_span;
int cpu;
build_balance_mask(sd, sg, mask);
cpu = cpumask_first(mask);
sg->sgc = *per_cpu_ptr(sdd->sgc, cpu);
if (atomic_inc_return(&sg->sgc->ref) == 1)
cpumask_copy(group_balance_mask(sg), mask);
else
WARN_ON_ONCE(!cpumask_equal(group_balance_mask(sg), mask));
/*
* Initialize sgc->capacity such that even if we mess up the
* domains and no possible iteration will get us here, we won't
* die on a /0 trap.
*/
sg_span = sched_group_span(sg);
sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;
}
static struct sched_domain *
find_descended_sibling(struct sched_domain *sd, struct sched_domain *sibling)
{
/*
* The proper descendant would be the one whose child won't span out
* of sd
*/
while (sibling->child &&
!cpumask_subset(sched_domain_span(sibling->child),
sched_domain_span(sd)))
sibling = sibling->child;
/*
* As we are referencing sgc across different topology level, we need
* to go down to skip those sched_domains which don't contribute to
* scheduling because they will be degenerated in cpu_attach_domain
*/
while (sibling->child &&
cpumask_equal(sched_domain_span(sibling->child),
sched_domain_span(sibling)))
sibling = sibling->child;
return sibling;
}
static int
build_overlap_sched_groups(struct sched_domain *sd, int cpu)
{
struct sched_group *first = NULL, *last = NULL, *sg;
const struct cpumask *span = sched_domain_span(sd);
struct cpumask *covered = sched_domains_tmpmask;
struct sd_data *sdd = sd->private;
struct sched_domain *sibling;
int i;
cpumask_clear(covered);
for_each_cpu_wrap(i, span, cpu) {
struct cpumask *sg_span;
if (cpumask_test_cpu(i, covered))
continue;
sibling = *per_cpu_ptr(sdd->sd, i);
/*
* Asymmetric node setups can result in situations where the
* domain tree is of unequal depth, make sure to skip domains
* that already cover the entire range.
*
* In that case build_sched_domains() will have terminated the
* iteration early and our sibling sd spans will be empty.
* Domains should always include the CPU they're built on, so
* check that.
*/
if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
continue;
/*
* Usually we build sched_group by sibling's child sched_domain
* But for machines whose NUMA diameter are 3 or above, we move
* to build sched_group by sibling's proper descendant's child
* domain because sibling's child sched_domain will span out of
* the sched_domain being built as below.
*
* Smallest diameter=3 topology is:
*
* node 0 1 2 3
* 0: 10 20 30 40
* 1: 20 10 20 30
* 2: 30 20 10 20
* 3: 40 30 20 10
*
* 0 --- 1 --- 2 --- 3
*
* NUMA-3 0-3 N/A N/A 0-3
* groups: {0-2},{1-3} {1-3},{0-2}
*
* NUMA-2 0-2 0-3 0-3 1-3
* groups: {0-1},{1-3} {0-2},{2-3} {1-3},{0-1} {2-3},{0-2}
*
* NUMA-1 0-1 0-2 1-3 2-3
* groups: {0},{1} {1},{2},{0} {2},{3},{1} {3},{2}
*
* NUMA-0 0 1 2 3
*
* The NUMA-2 groups for nodes 0 and 3 are obviously buggered, as the
* group span isn't a subset of the domain span.
*/
if (sibling->child &&
!cpumask_subset(sched_domain_span(sibling->child), span))
sibling = find_descended_sibling(sd, sibling);
sg = build_group_from_child_sched_domain(sibling, cpu);
if (!sg)
goto fail;
sg_span = sched_group_span(sg);
cpumask_or(covered, covered, sg_span);
init_overlap_sched_group(sibling, sg);
if (!first)
first = sg;
if (last)
last->next = sg;
last = sg;
last->next = first;
}
sd->groups = first;
return 0;
fail:
free_sched_groups(first, 0);
return -ENOMEM;
}
/*
* Package topology (also see the load-balance blurb in fair.c)
*
* The scheduler builds a tree structure to represent a number of important
* topology features. By default (default_topology[]) these include:
*
* - Simultaneous multithreading (SMT)
* - Multi-Core Cache (MC)
* - Package (DIE)
*
* Where the last one more or less denotes everything up to a NUMA node.
*
* The tree consists of 3 primary data structures:
*
* sched_domain -> sched_group -> sched_group_capacity
* ^ ^ ^ ^
* `-' `-'
*
* The sched_domains are per-CPU and have a two way link (parent & child) and
* denote the ever growing mask of CPUs belonging to that level of topology.
*
* Each sched_domain has a circular (double) linked list of sched_group's, each
* denoting the domains of the level below (or individual CPUs in case of the
* first domain level). The sched_group linked by a sched_domain includes the
* CPU of that sched_domain [*].
*
* Take for instance a 2 threaded, 2 core, 2 cache cluster part:
*
* CPU 0 1 2 3 4 5 6 7
*
* DIE [ ]
* MC [ ] [ ]
* SMT [ ] [ ] [ ] [ ]
*
* - or -
*
* DIE 0-7 0-7 0-7 0-7 0-7 0-7 0-7 0-7
* MC 0-3 0-3 0-3 0-3 4-7 4-7 4-7 4-7
* SMT 0-1 0-1 2-3 2-3 4-5 4-5 6-7 6-7
*
* CPU 0 1 2 3 4 5 6 7
*
* One way to think about it is: sched_domain moves you up and down among these
* topology levels, while sched_group moves you sideways through it, at child
* domain granularity.
*
* sched_group_capacity ensures each unique sched_group has shared storage.
*
* There are two related construction problems, both require a CPU that
* uniquely identify each group (for a given domain):
*
* - The first is the balance_cpu (see should_we_balance() and the
* load-balance blub in fair.c); for each group we only want 1 CPU to
* continue balancing at a higher domain.
*
* - The second is the sched_group_capacity; we want all identical groups
* to share a single sched_group_capacity.
*
* Since these topologies are exclusive by construction. That is, its
* impossible for an SMT thread to belong to multiple cores, and cores to
* be part of multiple caches. There is a very clear and unique location
* for each CPU in the hierarchy.
*
* Therefore computing a unique CPU for each group is trivial (the iteration
* mask is redundant and set all 1s; all CPUs in a group will end up at _that_
* group), we can simply pick the first CPU in each group.
*
*
* [*] in other words, the first group of each domain is its child domain.
*/
static struct sched_group *get_group(int cpu, struct sd_data *sdd)
{
struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
struct sched_domain *child = sd->child;
struct sched_group *sg;
bool already_visited;
if (child)
cpu = cpumask_first(sched_domain_span(child));
sg = *per_cpu_ptr(sdd->sg, cpu);
sg->sgc = *per_cpu_ptr(sdd->sgc, cpu);
/* Increase refcounts for claim_allocations: */
already_visited = atomic_inc_return(&sg->ref) > 1;
/* sgc visits should follow a similar trend as sg */
WARN_ON(already_visited != (atomic_inc_return(&sg->sgc->ref) > 1));
/* If we have already visited that group, it's already initialized. */
if (already_visited)
return sg;
if (child) {
cpumask_copy(sched_group_span(sg), sched_domain_span(child));
cpumask_copy(group_balance_mask(sg), sched_group_span(sg));
} else {
cpumask_set_cpu(cpu, sched_group_span(sg));
cpumask_set_cpu(cpu, group_balance_mask(sg));
}
sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sched_group_span(sg));
sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;
return sg;
}
/*
* build_sched_groups will build a circular linked list of the groups
* covered by the given span, will set each group's ->cpumask correctly,
* and will initialize their ->sgc.
*
* Assumes the sched_domain tree is fully constructed
*/
static int
build_sched_groups(struct sched_domain *sd, int cpu)
{
struct sched_group *first = NULL, *last = NULL;
struct sd_data *sdd = sd->private;
const struct cpumask *span = sched_domain_span(sd);
struct cpumask *covered;
int i;
lockdep_assert_held(&sched_domains_mutex);
covered = sched_domains_tmpmask;
cpumask_clear(covered);
for_each_cpu_wrap(i, span, cpu) {
struct sched_group *sg;
if (cpumask_test_cpu(i, covered))
continue;
sg = get_group(i, sdd);
cpumask_or(covered, covered, sched_group_span(sg));
if (!first)
first = sg;
if (last)
last->next = sg;
last = sg;
}
last->next = first;
sd->groups = first;
return 0;
}
/*
* Initialize sched groups cpu_capacity.
*
* cpu_capacity indicates the capacity of sched group, which is used while
* distributing the load between different sched groups in a sched domain.
* Typically cpu_capacity for all the groups in a sched domain will be same
* unless there are asymmetries in the topology. If there are asymmetries,
* group having more cpu_capacity will pickup more load compared to the
* group having less cpu_capacity.
*/
static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
{
struct sched_group *sg = sd->groups;
WARN_ON(!sg);
do {
int cpu, max_cpu = -1;
sg->group_weight = cpumask_weight(sched_group_span(sg));
if (!(sd->flags & SD_ASYM_PACKING))
goto next;
for_each_cpu(cpu, sched_group_span(sg)) {
if (max_cpu < 0)
max_cpu = cpu;
else if (sched_asym_prefer(cpu, max_cpu))
max_cpu = cpu;
}
sg->asym_prefer_cpu = max_cpu;
next:
sg = sg->next;
} while (sg != sd->groups);
if (cpu != group_balance_cpu(sg))
return;
update_group_capacity(sd, cpu);
}
/*
* Asymmetric CPU capacity bits
*/
struct asym_cap_data {
struct list_head link;
unsigned long capacity;
unsigned long cpus[];
};
/*
* Set of available CPUs grouped by their corresponding capacities
* Each list entry contains a CPU mask reflecting CPUs that share the same
* capacity.
* The lifespan of data is unlimited.
*/
static LIST_HEAD(asym_cap_list);
#define cpu_capacity_span(asym_data) to_cpumask((asym_data)->cpus)
/*
* Verify whether there is any CPU capacity asymmetry in a given sched domain.
* Provides sd_flags reflecting the asymmetry scope.
*/
static inline int
asym_cpu_capacity_classify(const struct cpumask *sd_span,
const struct cpumask *cpu_map)
{
struct asym_cap_data *entry;
int count = 0, miss = 0;
/*
* Count how many unique CPU capacities this domain spans across
* (compare sched_domain CPUs mask with ones representing available
* CPUs capacities). Take into account CPUs that might be offline:
* skip those.
*/
list_for_each_entry(entry, &asym_cap_list, link) {
if (cpumask_intersects(sd_span, cpu_capacity_span(entry)))
++count;
else if (cpumask_intersects(cpu_map, cpu_capacity_span(entry)))
++miss;
}
WARN_ON_ONCE(!count && !list_empty(&asym_cap_list));
/* No asymmetry detected */
if (count < 2)
return 0;
/* Some of the available CPU capacity values have not been detected */
if (miss)
return SD_ASYM_CPUCAPACITY;
/* Full asymmetry */
return SD_ASYM_CPUCAPACITY | SD_ASYM_CPUCAPACITY_FULL;
}
static inline void asym_cpu_capacity_update_data(int cpu)
{
unsigned long capacity = arch_scale_cpu_capacity(cpu);
struct asym_cap_data *entry = NULL;
list_for_each_entry(entry, &asym_cap_list, link) {
if (capacity == entry->capacity)
goto done;
}
entry = kzalloc(sizeof(*entry) + cpumask_size(), GFP_KERNEL);
if (WARN_ONCE(!entry, "Failed to allocate memory for asymmetry data\n"))
return;
entry->capacity = capacity;
list_add(&entry->link, &asym_cap_list);
done:
__cpumask_set_cpu(cpu, cpu_capacity_span(entry));
}
/*
* Build-up/update list of CPUs grouped by their capacities
* An update requires explicit request to rebuild sched domains
* with state indicating CPU topology changes.
*/
static void asym_cpu_capacity_scan(void)
{
struct asym_cap_data *entry, *next;
int cpu;
list_for_each_entry(entry, &asym_cap_list, link)
cpumask_clear(cpu_capacity_span(entry));
for_each_cpu_and(cpu, cpu_possible_mask, housekeeping_cpumask(HK_FLAG_DOMAIN))
asym_cpu_capacity_update_data(cpu);
list_for_each_entry_safe(entry, next, &asym_cap_list, link) {
if (cpumask_empty(cpu_capacity_span(entry))) {
list_del(&entry->link);
kfree(entry);
}
}
/*
* Only one capacity value has been detected i.e. this system is symmetric.
* No need to keep this data around.
*/
if (list_is_singular(&asym_cap_list)) {
entry = list_first_entry(&asym_cap_list, typeof(*entry), link);
list_del(&entry->link);
kfree(entry);
}
}
/*
* Initializers for schedule domains
* Non-inlined to reduce accumulated stack pressure in build_sched_domains()
*/
static int default_relax_domain_level = -1;
int sched_domain_level_max;
static int __init setup_relax_domain_level(char *str)
{
if (kstrtoint(str, 0, &default_relax_domain_level))
pr_warn("Unable to set relax_domain_level\n");
return 1;
}
__setup("relax_domain_level=", setup_relax_domain_level);
static void set_domain_attribute(struct sched_domain *sd,
struct sched_domain_attr *attr)
{
int request;
if (!attr || attr->relax_domain_level < 0) {
if (default_relax_domain_level < 0)
return;
request = default_relax_domain_level;
} else
request = attr->relax_domain_level;
if (sd->level > request) {
/* Turn off idle balance on this domain: */
sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
}
}
static void __sdt_free(const struct cpumask *cpu_map);
static int __sdt_alloc(const struct cpumask *cpu_map);
static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
const struct cpumask *cpu_map)
{
switch (what) {
case sa_rootdomain:
if (!atomic_read(&d->rd->refcount))
free_rootdomain(&d->rd->rcu);
fallthrough;
case sa_sd:
free_percpu(d->sd);
fallthrough;
case sa_sd_storage:
__sdt_free(cpu_map);
fallthrough;
case sa_none:
break;
}
}
static enum s_alloc
__visit_domain_allocation_hell(struct s_data *d, const struct cpumask *cpu_map)
{
memset(d, 0, sizeof(*d));
if (__sdt_alloc(cpu_map))
return sa_sd_storage;
d->sd = alloc_percpu(struct sched_domain *);
if (!d->sd)
return sa_sd_storage;
d->rd = alloc_rootdomain();
if (!d->rd)
return sa_sd;
return sa_rootdomain;
}
/*
* NULL the sd_data elements we've used to build the sched_domain and
* sched_group structure so that the subsequent __free_domain_allocs()
* will not free the data we're using.
*/
static void claim_allocations(int cpu, struct sched_domain *sd)
{
struct sd_data *sdd = sd->private;
WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
*per_cpu_ptr(sdd->sd, cpu) = NULL;
if (atomic_read(&(*per_cpu_ptr(sdd->sds, cpu))->ref))
*per_cpu_ptr(sdd->sds, cpu) = NULL;
if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
*per_cpu_ptr(sdd->sg, cpu) = NULL;
if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref))
*per_cpu_ptr(sdd->sgc, cpu) = NULL;
}
#ifdef CONFIG_NUMA
enum numa_topology_type sched_numa_topology_type;
static int sched_domains_numa_levels;
static int sched_domains_curr_level;
int sched_max_numa_distance;
static int *sched_domains_numa_distance;
static struct cpumask ***sched_domains_numa_masks;
int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;
#endif
/*
* SD_flags allowed in topology descriptions.
*
* These flags are purely descriptive of the topology and do not prescribe
* behaviour. Behaviour is artificial and mapped in the below sd_init()
* function:
*
* SD_SHARE_CPUCAPACITY - describes SMT topologies
* SD_SHARE_PKG_RESOURCES - describes shared caches
* SD_NUMA - describes NUMA topologies
*
* Odd one out, which beside describing the topology has a quirk also
* prescribes the desired behaviour that goes along with it:
*
* SD_ASYM_PACKING - describes SMT quirks
*/
#define TOPOLOGY_SD_FLAGS \
(SD_SHARE_CPUCAPACITY | \
SD_SHARE_PKG_RESOURCES | \
SD_NUMA | \
SD_ASYM_PACKING)
static struct sched_domain *
sd_init(struct sched_domain_topology_level *tl,
const struct cpumask *cpu_map,
struct sched_domain *child, int cpu)
{
struct sd_data *sdd = &tl->data;
struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
int sd_id, sd_weight, sd_flags = 0;
struct cpumask *sd_span;
#ifdef CONFIG_NUMA
/*
* Ugly hack to pass state to sd_numa_mask()...
*/
sched_domains_curr_level = tl->numa_level;
#endif
sd_weight = cpumask_weight(tl->mask(cpu));
if (tl->sd_flags)
sd_flags = (*tl->sd_flags)();
if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS,
"wrong sd_flags in topology description\n"))
sd_flags &= TOPOLOGY_SD_FLAGS;
*sd = (struct sched_domain){
.min_interval = sd_weight,
.max_interval = 2*sd_weight,
.busy_factor = 16,
.imbalance_pct = 117,
.cache_nice_tries = 0,
.flags = 1*SD_BALANCE_NEWIDLE
| 1*SD_BALANCE_EXEC
| 1*SD_BALANCE_FORK
| 0*SD_BALANCE_WAKE
| 1*SD_WAKE_AFFINE
| 0*SD_SHARE_CPUCAPACITY
| 0*SD_SHARE_PKG_RESOURCES
| 0*SD_SERIALIZE
| 1*SD_PREFER_SIBLING
| 0*SD_NUMA
| sd_flags
,
.last_balance = jiffies,
.balance_interval = sd_weight,
.max_newidle_lb_cost = 0,
.next_decay_max_lb_cost = jiffies,
.child = child,
#ifdef CONFIG_SCHED_DEBUG
.name = tl->name,
#endif
};
sd_span = sched_domain_span(sd);
cpumask_and(sd_span, cpu_map, tl->mask(cpu));
sd_id = cpumask_first(sd_span);
sd->flags |= asym_cpu_capacity_classify(sd_span, cpu_map);
WARN_ONCE((sd->flags & (SD_SHARE_CPUCAPACITY | SD_ASYM_CPUCAPACITY)) ==
(SD_SHARE_CPUCAPACITY | SD_ASYM_CPUCAPACITY),
"CPU capacity asymmetry not supported on SMT\n");
/*
* Convert topological properties into behaviour.
*/
/* Don't attempt to spread across CPUs of different capacities. */
if ((sd->flags & SD_ASYM_CPUCAPACITY) && sd->child)
sd->child->flags &= ~SD_PREFER_SIBLING;
if (sd->flags & SD_SHARE_CPUCAPACITY) {
sd->imbalance_pct = 110;
} else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
sd->imbalance_pct = 117;
sd->cache_nice_tries = 1;
#ifdef CONFIG_NUMA
} else if (sd->flags & SD_NUMA) {
sd->cache_nice_tries = 2;
sd->flags &= ~SD_PREFER_SIBLING;
sd->flags |= SD_SERIALIZE;
if (sched_domains_numa_distance[tl->numa_level] > node_reclaim_distance) {
sd->flags &= ~(SD_BALANCE_EXEC |
SD_BALANCE_FORK |
SD_WAKE_AFFINE);
}
#endif
} else {
sd->cache_nice_tries = 1;
}
/*
* For all levels sharing cache; connect a sched_domain_shared
* instance.
*/
if (sd->flags & SD_SHARE_PKG_RESOURCES) {
sd->shared = *per_cpu_ptr(sdd->sds, sd_id);
atomic_inc(&sd->shared->ref);
atomic_set(&sd->shared->nr_busy_cpus, sd_weight);
}
sd->private = sdd;
return sd;
}
/*
* Topology list, bottom-up.
*/
static struct sched_domain_topology_level default_topology[] = {
#ifdef CONFIG_SCHED_SMT
{ cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
#endif
#ifdef CONFIG_SCHED_MC
{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
#endif
{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
{ NULL, },
};
static struct sched_domain_topology_level *sched_domain_topology =
default_topology;
#define for_each_sd_topology(tl) \
for (tl = sched_domain_topology; tl->mask; tl++)
void set_sched_topology(struct sched_domain_topology_level *tl)
{
if (WARN_ON_ONCE(sched_smp_initialized))
return;
sched_domain_topology = tl;
}
#ifdef CONFIG_NUMA
static const struct cpumask *sd_numa_mask(int cpu)
{
return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
}
static void sched_numa_warn(const char *str)
{
static int done = false;
int i,j;
if (done)
return;
done = true;
printk(KERN_WARNING "ERROR: %s\n\n", str);
for (i = 0; i < nr_node_ids; i++) {
printk(KERN_WARNING " ");
for (j = 0; j < nr_node_ids; j++)
printk(KERN_CONT "%02d ", node_distance(i,j));
printk(KERN_CONT "\n");
}
printk(KERN_WARNING "\n");
}
bool find_numa_distance(int distance)
{
int i;
if (distance == node_distance(0, 0))
return true;
for (i = 0; i < sched_domains_numa_levels; i++) {
if (sched_domains_numa_distance[i] == distance)
return true;
}
return false;
}
/*
* A system can have three types of NUMA topology:
* NUMA_DIRECT: all nodes are directly connected, or not a NUMA system
* NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes
* NUMA_BACKPLANE: nodes can reach other nodes through a backplane
*
* The difference between a glueless mesh topology and a backplane
* topology lies in whether communication between not directly
* connected nodes goes through intermediary nodes (where programs
* could run), or through backplane controllers. This affects
* placement of programs.
*
* The type of topology can be discerned with the following tests:
* - If the maximum distance between any nodes is 1 hop, the system
* is directly connected.
* - If for two nodes A and B, located N > 1 hops away from each other,
* there is an intermediary node C, which is < N hops away from both
* nodes A and B, the system is a glueless mesh.
*/
static void init_numa_topology_type(void)
{
int a, b, c, n;
n = sched_max_numa_distance;
if (sched_domains_numa_levels <= 2) {
sched_numa_topology_type = NUMA_DIRECT;
return;
}
for_each_online_node(a) {
for_each_online_node(b) {
/* Find two nodes furthest removed from each other. */
if (node_distance(a, b) < n)
continue;
/* Is there an intermediary node between a and b? */
for_each_online_node(c) {
if (node_distance(a, c) < n &&
node_distance(b, c) < n) {
sched_numa_topology_type =
NUMA_GLUELESS_MESH;
return;
}
}
sched_numa_topology_type = NUMA_BACKPLANE;
return;
}
}
}
#define NR_DISTANCE_VALUES (1 << DISTANCE_BITS)
void sched_init_numa(void)
{
struct sched_domain_topology_level *tl;
unsigned long *distance_map;
int nr_levels = 0;
int i, j;
/*
* O(nr_nodes^2) deduplicating selection sort -- in order to find the
* unique distances in the node_distance() table.
*/
distance_map = bitmap_alloc(NR_DISTANCE_VALUES, GFP_KERNEL);
if (!distance_map)
return;
bitmap_zero(distance_map, NR_DISTANCE_VALUES);
for (i = 0; i < nr_node_ids; i++) {
for (j = 0; j < nr_node_ids; j++) {
int distance = node_distance(i, j);
if (distance < LOCAL_DISTANCE || distance >= NR_DISTANCE_VALUES) {
sched_numa_warn("Invalid distance value range");
return;
}
bitmap_set(distance_map, distance, 1);
}
}
/*
* We can now figure out how many unique distance values there are and
* allocate memory accordingly.
*/
nr_levels = bitmap_weight(distance_map, NR_DISTANCE_VALUES);
sched_domains_numa_distance = kcalloc(nr_levels, sizeof(int), GFP_KERNEL);
if (!sched_domains_numa_distance) {
bitmap_free(distance_map);
return;
}
for (i = 0, j = 0; i < nr_levels; i++, j++) {
j = find_next_bit(distance_map, NR_DISTANCE_VALUES, j);
sched_domains_numa_distance[i] = j;
}
bitmap_free(distance_map);
/*
* 'nr_levels' contains the number of unique distances
*
* The sched_domains_numa_distance[] array includes the actual distance
* numbers.
*/
/*
* Here, we should temporarily reset sched_domains_numa_levels to 0.
* If it fails to allocate memory for array sched_domains_numa_masks[][],
* the array will contain less then 'nr_levels' members. This could be
* dangerous when we use it to iterate array sched_domains_numa_masks[][]
* in other functions.
*
* We reset it to 'nr_levels' at the end of this function.
*/
sched_domains_numa_levels = 0;
sched_domains_numa_masks = kzalloc(sizeof(void *) * nr_levels, GFP_KERNEL);
if (!sched_domains_numa_masks)
return;
/*
* Now for each level, construct a mask per node which contains all
* CPUs of nodes that are that many hops away from us.
*/
for (i = 0; i < nr_levels; i++) {
sched_domains_numa_masks[i] =
kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
if (!sched_domains_numa_masks[i])
return;
for (j = 0; j < nr_node_ids; j++) {
struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
int k;
if (!mask)
return;
sched_domains_numa_masks[i][j] = mask;
for_each_node(k) {
if (sched_debug() && (node_distance(j, k) != node_distance(k, j)))
sched_numa_warn("Node-distance not symmetric");
if (node_distance(j, k) > sched_domains_numa_distance[i])
continue;
cpumask_or(mask, mask, cpumask_of_node(k));
}
}
}
/* Compute default topology size */
for (i = 0; sched_domain_topology[i].mask; i++);
tl = kzalloc((i + nr_levels + 1) *
sizeof(struct sched_domain_topology_level), GFP_KERNEL);
if (!tl)
return;
/*
* Copy the default topology bits..
*/
for (i = 0; sched_domain_topology[i].mask; i++)
tl[i] = sched_domain_topology[i];
/*
* Add the NUMA identity distance, aka single NODE.
*/
tl[i++] = (struct sched_domain_topology_level){
.mask = sd_numa_mask,
.numa_level = 0,
SD_INIT_NAME(NODE)
};
/*
* .. and append 'j' levels of NUMA goodness.
*/
for (j = 1; j < nr_levels; i++, j++) {
tl[i] = (struct sched_domain_topology_level){
.mask = sd_numa_mask,
.sd_flags = cpu_numa_flags,
.flags = SDTL_OVERLAP,
.numa_level = j,
SD_INIT_NAME(NUMA)
};
}
sched_domain_topology = tl;
sched_domains_numa_levels = nr_levels;
sched_max_numa_distance = sched_domains_numa_distance[nr_levels - 1];
init_numa_topology_type();
}
void sched_domains_numa_masks_set(unsigned int cpu)
{
int node = cpu_to_node(cpu);
int i, j;
for (i = 0; i < sched_domains_numa_levels; i++) {
for (j = 0; j < nr_node_ids; j++) {
if (node_distance(j, node) <= sched_domains_numa_distance[i])
cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
}
}
}
void sched_domains_numa_masks_clear(unsigned int cpu)
{
int i, j;
for (i = 0; i < sched_domains_numa_levels; i++) {
for (j = 0; j < nr_node_ids; j++)
cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
}
}
/*
* sched_numa_find_closest() - given the NUMA topology, find the cpu
* closest to @cpu from @cpumask.
* cpumask: cpumask to find a cpu from
* cpu: cpu to be close to
*
* returns: cpu, or nr_cpu_ids when nothing found.
*/
int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
{
int i, j = cpu_to_node(cpu);
for (i = 0; i < sched_domains_numa_levels; i++) {
cpu = cpumask_any_and(cpus, sched_domains_numa_masks[i][j]);
if (cpu < nr_cpu_ids)
return cpu;
}
return nr_cpu_ids;
}
#endif /* CONFIG_NUMA */
static int __sdt_alloc(const struct cpumask *cpu_map)
{
struct sched_domain_topology_level *tl;
int j;
for_each_sd_topology(tl) {
struct sd_data *sdd = &tl->data;
sdd->sd = alloc_percpu(struct sched_domain *);
if (!sdd->sd)
return -ENOMEM;
sdd->sds = alloc_percpu(struct sched_domain_shared *);
if (!sdd->sds)
return -ENOMEM;
sdd->sg = alloc_percpu(struct sched_group *);
if (!sdd->sg)
return -ENOMEM;
sdd->sgc = alloc_percpu(struct sched_group_capacity *);
if (!sdd->sgc)
return -ENOMEM;
for_each_cpu(j, cpu_map) {
struct sched_domain *sd;
struct sched_domain_shared *sds;
struct sched_group *sg;
struct sched_group_capacity *sgc;
sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
GFP_KERNEL, cpu_to_node(j));
if (!sd)
return -ENOMEM;
*per_cpu_ptr(sdd->sd, j) = sd;
sds = kzalloc_node(sizeof(struct sched_domain_shared),
GFP_KERNEL, cpu_to_node(j));
if (!sds)
return -ENOMEM;
*per_cpu_ptr(sdd->sds, j) = sds;
sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
GFP_KERNEL, cpu_to_node(j));
if (!sg)
return -ENOMEM;
sg->next = sg;
*per_cpu_ptr(sdd->sg, j) = sg;
sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(),
GFP_KERNEL, cpu_to_node(j));
if (!sgc)
return -ENOMEM;
#ifdef CONFIG_SCHED_DEBUG
sgc->id = j;
#endif
*per_cpu_ptr(sdd->sgc, j) = sgc;
}
}
return 0;
}
static void __sdt_free(const struct cpumask *cpu_map)
{
struct sched_domain_topology_level *tl;
int j;
for_each_sd_topology(tl) {
struct sd_data *sdd = &tl->data;
for_each_cpu(j, cpu_map) {
struct sched_domain *sd;
if (sdd->sd) {
sd = *per_cpu_ptr(sdd->sd, j);
if (sd && (sd->flags & SD_OVERLAP))
free_sched_groups(sd->groups, 0);
kfree(*per_cpu_ptr(sdd->sd, j));
}
if (sdd->sds)
kfree(*per_cpu_ptr(sdd->sds, j));
if (sdd->sg)
kfree(*per_cpu_ptr(sdd->sg, j));
if (sdd->sgc)
kfree(*per_cpu_ptr(sdd->sgc, j));
}
free_percpu(sdd->sd);
sdd->sd = NULL;
free_percpu(sdd->sds);
sdd->sds = NULL;
free_percpu(sdd->sg);
sdd->sg = NULL;
free_percpu(sdd->sgc);
sdd->sgc = NULL;
}
}
static struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
const struct cpumask *cpu_map, struct sched_domain_attr *attr,
struct sched_domain *child, int cpu)
{
struct sched_domain *sd = sd_init(tl, cpu_map, child, cpu);
if (child) {
sd->level = child->level + 1;
sched_domain_level_max = max(sched_domain_level_max, sd->level);
child->parent = sd;
if (!cpumask_subset(sched_domain_span(child),
sched_domain_span(sd))) {
pr_err("BUG: arch topology borken\n");
#ifdef CONFIG_SCHED_DEBUG
pr_err(" the %s domain not a subset of the %s domain\n",
child->name, sd->name);
#endif
/* Fixup, ensure @sd has at least @child CPUs. */
cpumask_or(sched_domain_span(sd),
sched_domain_span(sd),
sched_domain_span(child));
}
}
set_domain_attribute(sd, attr);
return sd;
}
/*
* Ensure topology masks are sane, i.e. there are no conflicts (overlaps) for
* any two given CPUs at this (non-NUMA) topology level.
*/
static bool topology_span_sane(struct sched_domain_topology_level *tl,
const struct cpumask *cpu_map, int cpu)
{
int i;
/* NUMA levels are allowed to overlap */
if (tl->flags & SDTL_OVERLAP)
return true;
/*
* Non-NUMA levels cannot partially overlap - they must be either
* completely equal or completely disjoint. Otherwise we can end up
* breaking the sched_group lists - i.e. a later get_group() pass
* breaks the linking done for an earlier span.
*/
for_each_cpu(i, cpu_map) {
if (i == cpu)
continue;
/*
* We should 'and' all those masks with 'cpu_map' to exactly
* match the topology we're about to build, but that can only
* remove CPUs, which only lessens our ability to detect
* overlaps
*/
if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) &&
cpumask_intersects(tl->mask(cpu), tl->mask(i)))
return false;
}
return true;
}
/*
* Build sched domains for a given set of CPUs and attach the sched domains
* to the individual CPUs
*/
static int
build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *attr)
{
enum s_alloc alloc_state = sa_none;
struct sched_domain *sd;
struct s_data d;
struct rq *rq = NULL;
int i, ret = -ENOMEM;
bool has_asym = false;
if (WARN_ON(cpumask_empty(cpu_map)))
goto error;
alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
if (alloc_state != sa_rootdomain)
goto error;
/* Set up domains for CPUs specified by the cpu_map: */
for_each_cpu(i, cpu_map) {
struct sched_domain_topology_level *tl;
sd = NULL;
for_each_sd_topology(tl) {
if (WARN_ON(!topology_span_sane(tl, cpu_map, i)))
goto error;
sd = build_sched_domain(tl, cpu_map, attr, sd, i);
has_asym |= sd->flags & SD_ASYM_CPUCAPACITY;
if (tl == sched_domain_topology)
*per_cpu_ptr(d.sd, i) = sd;
if (tl->flags & SDTL_OVERLAP)
sd->flags |= SD_OVERLAP;
if (cpumask_equal(cpu_map, sched_domain_span(sd)))
break;
}
}
/* Build the groups for the domains */
for_each_cpu(i, cpu_map) {
for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
sd->span_weight = cpumask_weight(sched_domain_span(sd));
if (sd->flags & SD_OVERLAP) {
if (build_overlap_sched_groups(sd, i))
goto error;
} else {
if (build_sched_groups(sd, i))
goto error;
}
}
}
/* Calculate CPU capacity for physical packages and nodes */
for (i = nr_cpumask_bits-1; i >= 0; i--) {
if (!cpumask_test_cpu(i, cpu_map))
continue;
for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
claim_allocations(i, sd);
init_sched_groups_capacity(i, sd);
}
}
/* Attach the domains */
rcu_read_lock();
for_each_cpu(i, cpu_map) {
rq = cpu_rq(i);
sd = *per_cpu_ptr(d.sd, i);
/* Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing: */
if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity))
WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig);
cpu_attach_domain(sd, d.rd, i);
}
rcu_read_unlock();
if (has_asym)
static_branch_inc_cpuslocked(&sched_asym_cpucapacity);
if (rq && sched_debug_verbose) {
pr_info("root domain span: %*pbl (max cpu_capacity = %lu)\n",
cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
}
ret = 0;
error:
__free_domain_allocs(&d, alloc_state, cpu_map);
return ret;
}
/* Current sched domains: */
static cpumask_var_t *doms_cur;
/* Number of sched domains in 'doms_cur': */
static int ndoms_cur;
/* Attributes of custom domains in 'doms_cur' */
static struct sched_domain_attr *dattr_cur;
/*
* Special case: If a kmalloc() of a doms_cur partition (array of
* cpumask) fails, then fallback to a single sched domain,
* as determined by the single cpumask fallback_doms.
*/
static cpumask_var_t fallback_doms;
/*
* arch_update_cpu_topology lets virtualized architectures update the
* CPU core maps. It is supposed to return 1 if the topology changed
* or 0 if it stayed the same.
*/
int __weak arch_update_cpu_topology(void)
{
return 0;
}
cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
{
int i;
cpumask_var_t *doms;
doms = kmalloc_array(ndoms, sizeof(*doms), GFP_KERNEL);
if (!doms)
return NULL;
for (i = 0; i < ndoms; i++) {
if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
free_sched_domains(doms, i);
return NULL;
}
}
return doms;
}
void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
{
unsigned int i;
for (i = 0; i < ndoms; i++)
free_cpumask_var(doms[i]);
kfree(doms);
}
/*
* Set up scheduler domains and groups. For now this just excludes isolated
* CPUs, but could be used to exclude other special cases in the future.
*/
int sched_init_domains(const struct cpumask *cpu_map)
{
int err;
zalloc_cpumask_var(&sched_domains_tmpmask, GFP_KERNEL);
zalloc_cpumask_var(&sched_domains_tmpmask2, GFP_KERNEL);
zalloc_cpumask_var(&fallback_doms, GFP_KERNEL);
arch_update_cpu_topology();
asym_cpu_capacity_scan();
ndoms_cur = 1;
doms_cur = alloc_sched_domains(ndoms_cur);
if (!doms_cur)
doms_cur = &fallback_doms;
cpumask_and(doms_cur[0], cpu_map, housekeeping_cpumask(HK_FLAG_DOMAIN));
err = build_sched_domains(doms_cur[0], NULL);
return err;
}
/*
* Detach sched domains from a group of CPUs specified in cpu_map
* These CPUs will now be attached to the NULL domain
*/
static void detach_destroy_domains(const struct cpumask *cpu_map)
{
unsigned int cpu = cpumask_any(cpu_map);
int i;
if (rcu_access_pointer(per_cpu(sd_asym_cpucapacity, cpu)))
static_branch_dec_cpuslocked(&sched_asym_cpucapacity);
rcu_read_lock();
for_each_cpu(i, cpu_map)
cpu_attach_domain(NULL, &def_root_domain, i);
rcu_read_unlock();
}
/* handle null as "default" */
static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
struct sched_domain_attr *new, int idx_new)
{
struct sched_domain_attr tmp;
/* Fast path: */
if (!new && !cur)
return 1;
tmp = SD_ATTR_INIT;
return !memcmp(cur ? (cur + idx_cur) : &tmp,
new ? (new + idx_new) : &tmp,
sizeof(struct sched_domain_attr));
}
/*
* Partition sched domains as specified by the 'ndoms_new'
* cpumasks in the array doms_new[] of cpumasks. This compares
* doms_new[] to the current sched domain partitioning, doms_cur[].
* It destroys each deleted domain and builds each new domain.
*
* 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
* The masks don't intersect (don't overlap.) We should setup one
* sched domain for each mask. CPUs not in any of the cpumasks will
* not be load balanced. If the same cpumask appears both in the
* current 'doms_cur' domains and in the new 'doms_new', we can leave
* it as it is.
*
* The passed in 'doms_new' should be allocated using
* alloc_sched_domains. This routine takes ownership of it and will
* free_sched_domains it when done with it. If the caller failed the
* alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
* and partition_sched_domains() will fallback to the single partition
* 'fallback_doms', it also forces the domains to be rebuilt.
*
* If doms_new == NULL it will be replaced with cpu_online_mask.
* ndoms_new == 0 is a special case for destroying existing domains,
* and it will not create the default domain.
*
* Call with hotplug lock and sched_domains_mutex held
*/
void partition_sched_domains_locked(int ndoms_new, cpumask_var_t doms_new[],
struct sched_domain_attr *dattr_new)
{
bool __maybe_unused has_eas = false;
int i, j, n;
int new_topology;
lockdep_assert_held(&sched_domains_mutex);
/* Let the architecture update CPU core mappings: */
new_topology = arch_update_cpu_topology();
/* Trigger rebuilding CPU capacity asymmetry data */
if (new_topology)
asym_cpu_capacity_scan();
if (!doms_new) {
WARN_ON_ONCE(dattr_new);
n = 0;
doms_new = alloc_sched_domains(1);
if (doms_new) {
n = 1;
cpumask_and(doms_new[0], cpu_active_mask,
housekeeping_cpumask(HK_FLAG_DOMAIN));
}
} else {
n = ndoms_new;
}
/* Destroy deleted domains: */
for (i = 0; i < ndoms_cur; i++) {
for (j = 0; j < n && !new_topology; j++) {
if (cpumask_equal(doms_cur[i], doms_new[j]) &&
dattrs_equal(dattr_cur, i, dattr_new, j)) {
struct root_domain *rd;
/*
* This domain won't be destroyed and as such
* its dl_bw->total_bw needs to be cleared. It
* will be recomputed in function
* update_tasks_root_domain().
*/
rd = cpu_rq(cpumask_any(doms_cur[i]))->rd;
dl_clear_root_domain(rd);
goto match1;
}
}
/* No match - a current sched domain not in new doms_new[] */
detach_destroy_domains(doms_cur[i]);
match1:
;
}
n = ndoms_cur;
if (!doms_new) {
n = 0;
doms_new = &fallback_doms;
cpumask_and(doms_new[0], cpu_active_mask,
housekeeping_cpumask(HK_FLAG_DOMAIN));
}
/* Build new domains: */
for (i = 0; i < ndoms_new; i++) {
for (j = 0; j < n && !new_topology; j++) {
if (cpumask_equal(doms_new[i], doms_cur[j]) &&
dattrs_equal(dattr_new, i, dattr_cur, j))
goto match2;
}
/* No match - add a new doms_new */
build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
match2:
;
}
#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
/* Build perf. domains: */
for (i = 0; i < ndoms_new; i++) {
for (j = 0; j < n && !sched_energy_update; j++) {
if (cpumask_equal(doms_new[i], doms_cur[j]) &&
cpu_rq(cpumask_first(doms_cur[j]))->rd->pd) {
has_eas = true;
goto match3;
}
}
/* No match - add perf. domains for a new rd */
has_eas |= build_perf_domains(doms_new[i]);
match3:
;
}
sched_energy_set(has_eas);
#endif
/* Remember the new sched domains: */
if (doms_cur != &fallback_doms)
free_sched_domains(doms_cur, ndoms_cur);
kfree(dattr_cur);
doms_cur = doms_new;
dattr_cur = dattr_new;
ndoms_cur = ndoms_new;
update_sched_domain_debugfs();
}
/*
* Call with hotplug lock held
*/
void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
struct sched_domain_attr *dattr_new)
{
mutex_lock(&sched_domains_mutex);
partition_sched_domains_locked(ndoms_new, doms_new, dattr_new);
mutex_unlock(&sched_domains_mutex);
}