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// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h>
#include <linux/lockdep.h>
#include <linux/sysfs.h>
#include <linux/kobject.h>
#include <linux/memory.h>
#include <linux/memory-tiers.h>
#include "internal.h"
struct memory_tier {
/* hierarchy of memory tiers */
struct list_head list;
/* list of all memory types part of this tier */
struct list_head memory_types;
/*
* start value of abstract distance. memory tier maps
* an abstract distance range,
* adistance_start .. adistance_start + MEMTIER_CHUNK_SIZE
*/
int adistance_start;
struct device dev;
/* All the nodes that are part of all the lower memory tiers. */
nodemask_t lower_tier_mask;
};
struct demotion_nodes {
nodemask_t preferred;
};
struct node_memory_type_map {
struct memory_dev_type *memtype;
int map_count;
};
static DEFINE_MUTEX(memory_tier_lock);
static LIST_HEAD(memory_tiers);
static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
static struct memory_dev_type *default_dram_type;
static struct bus_type memory_tier_subsys = {
.name = "memory_tiering",
.dev_name = "memory_tier",
};
#ifdef CONFIG_MIGRATION
static int top_tier_adistance;
/*
* node_demotion[] examples:
*
* Example 1:
*
* Node 0 & 1 are CPU + DRAM nodes, node 2 & 3 are PMEM nodes.
*
* node distances:
* node 0 1 2 3
* 0 10 20 30 40
* 1 20 10 40 30
* 2 30 40 10 40
* 3 40 30 40 10
*
* memory_tiers0 = 0-1
* memory_tiers1 = 2-3
*
* node_demotion[0].preferred = 2
* node_demotion[1].preferred = 3
* node_demotion[2].preferred = <empty>
* node_demotion[3].preferred = <empty>
*
* Example 2:
*
* Node 0 & 1 are CPU + DRAM nodes, node 2 is memory-only DRAM node.
*
* node distances:
* node 0 1 2
* 0 10 20 30
* 1 20 10 30
* 2 30 30 10
*
* memory_tiers0 = 0-2
*
* node_demotion[0].preferred = <empty>
* node_demotion[1].preferred = <empty>
* node_demotion[2].preferred = <empty>
*
* Example 3:
*
* Node 0 is CPU + DRAM nodes, Node 1 is HBM node, node 2 is PMEM node.
*
* node distances:
* node 0 1 2
* 0 10 20 30
* 1 20 10 40
* 2 30 40 10
*
* memory_tiers0 = 1
* memory_tiers1 = 0
* memory_tiers2 = 2
*
* node_demotion[0].preferred = 2
* node_demotion[1].preferred = 0
* node_demotion[2].preferred = <empty>
*
*/
static struct demotion_nodes *node_demotion __read_mostly;
#endif /* CONFIG_MIGRATION */
static inline struct memory_tier *to_memory_tier(struct device *device)
{
return container_of(device, struct memory_tier, dev);
}
static __always_inline nodemask_t get_memtier_nodemask(struct memory_tier *memtier)
{
nodemask_t nodes = NODE_MASK_NONE;
struct memory_dev_type *memtype;
list_for_each_entry(memtype, &memtier->memory_types, tier_sibiling)
nodes_or(nodes, nodes, memtype->nodes);
return nodes;
}
static void memory_tier_device_release(struct device *dev)
{
struct memory_tier *tier = to_memory_tier(dev);
/*
* synchronize_rcu in clear_node_memory_tier makes sure
* we don't have rcu access to this memory tier.
*/
kfree(tier);
}
static ssize_t nodelist_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
int ret;
nodemask_t nmask;
mutex_lock(&memory_tier_lock);
nmask = get_memtier_nodemask(to_memory_tier(dev));
ret = sysfs_emit(buf, "%*pbl\n", nodemask_pr_args(&nmask));
mutex_unlock(&memory_tier_lock);
return ret;
}
static DEVICE_ATTR_RO(nodelist);
static struct attribute *memtier_dev_attrs[] = {
&dev_attr_nodelist.attr,
NULL
};
static const struct attribute_group memtier_dev_group = {
.attrs = memtier_dev_attrs,
};
static const struct attribute_group *memtier_dev_groups[] = {
&memtier_dev_group,
NULL
};
static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memtype)
{
int ret;
bool found_slot = false;
struct memory_tier *memtier, *new_memtier;
int adistance = memtype->adistance;
unsigned int memtier_adistance_chunk_size = MEMTIER_CHUNK_SIZE;
lockdep_assert_held_once(&memory_tier_lock);
adistance = round_down(adistance, memtier_adistance_chunk_size);
/*
* If the memtype is already part of a memory tier,
* just return that.
*/
if (!list_empty(&memtype->tier_sibiling)) {
list_for_each_entry(memtier, &memory_tiers, list) {
if (adistance == memtier->adistance_start)
return memtier;
}
WARN_ON(1);
return ERR_PTR(-EINVAL);
}
list_for_each_entry(memtier, &memory_tiers, list) {
if (adistance == memtier->adistance_start) {
goto link_memtype;
} else if (adistance < memtier->adistance_start) {
found_slot = true;
break;
}
}
new_memtier = kzalloc(sizeof(struct memory_tier), GFP_KERNEL);
if (!new_memtier)
return ERR_PTR(-ENOMEM);
new_memtier->adistance_start = adistance;
INIT_LIST_HEAD(&new_memtier->list);
INIT_LIST_HEAD(&new_memtier->memory_types);
if (found_slot)
list_add_tail(&new_memtier->list, &memtier->list);
else
list_add_tail(&new_memtier->list, &memory_tiers);
new_memtier->dev.id = adistance >> MEMTIER_CHUNK_BITS;
new_memtier->dev.bus = &memory_tier_subsys;
new_memtier->dev.release = memory_tier_device_release;
new_memtier->dev.groups = memtier_dev_groups;
ret = device_register(&new_memtier->dev);
if (ret) {
list_del(&new_memtier->list);
put_device(&new_memtier->dev);
return ERR_PTR(ret);
}
memtier = new_memtier;
link_memtype:
list_add(&memtype->tier_sibiling, &memtier->memory_types);
return memtier;
}
static struct memory_tier *__node_get_memory_tier(int node)
{
pg_data_t *pgdat;
pgdat = NODE_DATA(node);
if (!pgdat)
return NULL;
/*
* Since we hold memory_tier_lock, we can avoid
* RCU read locks when accessing the details. No
* parallel updates are possible here.
*/
return rcu_dereference_check(pgdat->memtier,
lockdep_is_held(&memory_tier_lock));
}
#ifdef CONFIG_MIGRATION
bool node_is_toptier(int node)
{
bool toptier;
pg_data_t *pgdat;
struct memory_tier *memtier;
pgdat = NODE_DATA(node);
if (!pgdat)
return false;
rcu_read_lock();
memtier = rcu_dereference(pgdat->memtier);
if (!memtier) {
toptier = true;
goto out;
}
if (memtier->adistance_start <= top_tier_adistance)
toptier = true;
else
toptier = false;
out:
rcu_read_unlock();
return toptier;
}
void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)
{
struct memory_tier *memtier;
/*
* pg_data_t.memtier updates includes a synchronize_rcu()
* which ensures that we either find NULL or a valid memtier
* in NODE_DATA. protect the access via rcu_read_lock();
*/
rcu_read_lock();
memtier = rcu_dereference(pgdat->memtier);
if (memtier)
*targets = memtier->lower_tier_mask;
else
*targets = NODE_MASK_NONE;
rcu_read_unlock();
}
/**
* next_demotion_node() - Get the next node in the demotion path
* @node: The starting node to lookup the next node
*
* Return: node id for next memory node in the demotion path hierarchy
* from @node; NUMA_NO_NODE if @node is terminal. This does not keep
* @node online or guarantee that it *continues* to be the next demotion
* target.
*/
int next_demotion_node(int node)
{
struct demotion_nodes *nd;
int target;
if (!node_demotion)
return NUMA_NO_NODE;
nd = &node_demotion[node];
/*
* node_demotion[] is updated without excluding this
* function from running.
*
* Make sure to use RCU over entire code blocks if
* node_demotion[] reads need to be consistent.
*/
rcu_read_lock();
/*
* If there are multiple target nodes, just select one
* target node randomly.
*
* In addition, we can also use round-robin to select
* target node, but we should introduce another variable
* for node_demotion[] to record last selected target node,
* that may cause cache ping-pong due to the changing of
* last target node. Or introducing per-cpu data to avoid
* caching issue, which seems more complicated. So selecting
* target node randomly seems better until now.
*/
target = node_random(&nd->preferred);
rcu_read_unlock();
return target;
}
static void disable_all_demotion_targets(void)
{
struct memory_tier *memtier;
int node;
for_each_node_state(node, N_MEMORY) {
node_demotion[node].preferred = NODE_MASK_NONE;
/*
* We are holding memory_tier_lock, it is safe
* to access pgda->memtier.
*/
memtier = __node_get_memory_tier(node);
if (memtier)
memtier->lower_tier_mask = NODE_MASK_NONE;
}
/*
* Ensure that the "disable" is visible across the system.
* Readers will see either a combination of before+disable
* state or disable+after. They will never see before and
* after state together.
*/
synchronize_rcu();
}
/*
* Find an automatic demotion target for all memory
* nodes. Failing here is OK. It might just indicate
* being at the end of a chain.
*/
static void establish_demotion_targets(void)
{
struct memory_tier *memtier;
struct demotion_nodes *nd;
int target = NUMA_NO_NODE, node;
int distance, best_distance;
nodemask_t tier_nodes, lower_tier;
lockdep_assert_held_once(&memory_tier_lock);
if (!node_demotion || !IS_ENABLED(CONFIG_MIGRATION))
return;
disable_all_demotion_targets();
for_each_node_state(node, N_MEMORY) {
best_distance = -1;
nd = &node_demotion[node];
memtier = __node_get_memory_tier(node);
if (!memtier || list_is_last(&memtier->list, &memory_tiers))
continue;
/*
* Get the lower memtier to find the demotion node list.
*/
memtier = list_next_entry(memtier, list);
tier_nodes = get_memtier_nodemask(memtier);
/*
* find_next_best_node, use 'used' nodemask as a skip list.
* Add all memory nodes except the selected memory tier
* nodelist to skip list so that we find the best node from the
* memtier nodelist.
*/
nodes_andnot(tier_nodes, node_states[N_MEMORY], tier_nodes);
/*
* Find all the nodes in the memory tier node list of same best distance.
* add them to the preferred mask. We randomly select between nodes
* in the preferred mask when allocating pages during demotion.
*/
do {
target = find_next_best_node(node, &tier_nodes);
if (target == NUMA_NO_NODE)
break;
distance = node_distance(node, target);
if (distance == best_distance || best_distance == -1) {
best_distance = distance;
node_set(target, nd->preferred);
} else {
break;
}
} while (1);
}
/*
* Promotion is allowed from a memory tier to higher
* memory tier only if the memory tier doesn't include
* compute. We want to skip promotion from a memory tier,
* if any node that is part of the memory tier have CPUs.
* Once we detect such a memory tier, we consider that tier
* as top tiper from which promotion is not allowed.
*/
list_for_each_entry_reverse(memtier, &memory_tiers, list) {
tier_nodes = get_memtier_nodemask(memtier);
nodes_and(tier_nodes, node_states[N_CPU], tier_nodes);
if (!nodes_empty(tier_nodes)) {
/*
* abstract distance below the max value of this memtier
* is considered toptier.
*/
top_tier_adistance = memtier->adistance_start +
MEMTIER_CHUNK_SIZE - 1;
break;
}
}
/*
* Now build the lower_tier mask for each node collecting node mask from
* all memory tier below it. This allows us to fallback demotion page
* allocation to a set of nodes that is closer the above selected
* perferred node.
*/
lower_tier = node_states[N_MEMORY];
list_for_each_entry(memtier, &memory_tiers, list) {
/*
* Keep removing current tier from lower_tier nodes,
* This will remove all nodes in current and above
* memory tier from the lower_tier mask.
*/
tier_nodes = get_memtier_nodemask(memtier);
nodes_andnot(lower_tier, lower_tier, tier_nodes);
memtier->lower_tier_mask = lower_tier;
}
}
#else
static inline void disable_all_demotion_targets(void) {}
static inline void establish_demotion_targets(void) {}
#endif /* CONFIG_MIGRATION */
static inline void __init_node_memory_type(int node, struct memory_dev_type *memtype)
{
if (!node_memory_types[node].memtype)
node_memory_types[node].memtype = memtype;
/*
* for each device getting added in the same NUMA node
* with this specific memtype, bump the map count. We
* Only take memtype device reference once, so that
* changing a node memtype can be done by droping the
* only reference count taken here.
*/
if (node_memory_types[node].memtype == memtype) {
if (!node_memory_types[node].map_count++)
kref_get(&memtype->kref);
}
}
static struct memory_tier *set_node_memory_tier(int node)
{
struct memory_tier *memtier;
struct memory_dev_type *memtype;
pg_data_t *pgdat = NODE_DATA(node);
lockdep_assert_held_once(&memory_tier_lock);
if (!node_state(node, N_MEMORY))
return ERR_PTR(-EINVAL);
__init_node_memory_type(node, default_dram_type);
memtype = node_memory_types[node].memtype;
node_set(node, memtype->nodes);
memtier = find_create_memory_tier(memtype);
if (!IS_ERR(memtier))
rcu_assign_pointer(pgdat->memtier, memtier);
return memtier;
}
static void destroy_memory_tier(struct memory_tier *memtier)
{
list_del(&memtier->list);
device_unregister(&memtier->dev);
}
static bool clear_node_memory_tier(int node)
{
bool cleared = false;
pg_data_t *pgdat;
struct memory_tier *memtier;
pgdat = NODE_DATA(node);
if (!pgdat)
return false;
/*
* Make sure that anybody looking at NODE_DATA who finds
* a valid memtier finds memory_dev_types with nodes still
* linked to the memtier. We achieve this by waiting for
* rcu read section to finish using synchronize_rcu.
* This also enables us to free the destroyed memory tier
* with kfree instead of kfree_rcu
*/
memtier = __node_get_memory_tier(node);
if (memtier) {
struct memory_dev_type *memtype;
rcu_assign_pointer(pgdat->memtier, NULL);
synchronize_rcu();
memtype = node_memory_types[node].memtype;
node_clear(node, memtype->nodes);
if (nodes_empty(memtype->nodes)) {
list_del_init(&memtype->tier_sibiling);
if (list_empty(&memtier->memory_types))
destroy_memory_tier(memtier);
}
cleared = true;
}
return cleared;
}
static void release_memtype(struct kref *kref)
{
struct memory_dev_type *memtype;
memtype = container_of(kref, struct memory_dev_type, kref);
kfree(memtype);
}
struct memory_dev_type *alloc_memory_type(int adistance)
{
struct memory_dev_type *memtype;
memtype = kmalloc(sizeof(*memtype), GFP_KERNEL);
if (!memtype)
return ERR_PTR(-ENOMEM);
memtype->adistance = adistance;
INIT_LIST_HEAD(&memtype->tier_sibiling);
memtype->nodes = NODE_MASK_NONE;
kref_init(&memtype->kref);
return memtype;
}
EXPORT_SYMBOL_GPL(alloc_memory_type);
void destroy_memory_type(struct memory_dev_type *memtype)
{
kref_put(&memtype->kref, release_memtype);
}
EXPORT_SYMBOL_GPL(destroy_memory_type);
void init_node_memory_type(int node, struct memory_dev_type *memtype)
{
mutex_lock(&memory_tier_lock);
__init_node_memory_type(node, memtype);
mutex_unlock(&memory_tier_lock);
}
EXPORT_SYMBOL_GPL(init_node_memory_type);
void clear_node_memory_type(int node, struct memory_dev_type *memtype)
{
mutex_lock(&memory_tier_lock);
if (node_memory_types[node].memtype == memtype)
node_memory_types[node].map_count--;
/*
* If we umapped all the attached devices to this node,
* clear the node memory type.
*/
if (!node_memory_types[node].map_count) {
node_memory_types[node].memtype = NULL;
kref_put(&memtype->kref, release_memtype);
}
mutex_unlock(&memory_tier_lock);
}
EXPORT_SYMBOL_GPL(clear_node_memory_type);
static int __meminit memtier_hotplug_callback(struct notifier_block *self,
unsigned long action, void *_arg)
{
struct memory_tier *memtier;
struct memory_notify *arg = _arg;
/*
* Only update the node migration order when a node is
* changing status, like online->offline.
*/
if (arg->status_change_nid < 0)
return notifier_from_errno(0);
switch (action) {
case MEM_OFFLINE:
mutex_lock(&memory_tier_lock);
if (clear_node_memory_tier(arg->status_change_nid))
establish_demotion_targets();
mutex_unlock(&memory_tier_lock);
break;
case MEM_ONLINE:
mutex_lock(&memory_tier_lock);
memtier = set_node_memory_tier(arg->status_change_nid);
if (!IS_ERR(memtier))
establish_demotion_targets();
mutex_unlock(&memory_tier_lock);
break;
}
return notifier_from_errno(0);
}
static int __init memory_tier_init(void)
{
int ret, node;
struct memory_tier *memtier;
ret = subsys_virtual_register(&memory_tier_subsys, NULL);
if (ret)
panic("%s() failed to register memory tier subsystem\n", __func__);
#ifdef CONFIG_MIGRATION
node_demotion = kcalloc(nr_node_ids, sizeof(struct demotion_nodes),
GFP_KERNEL);
WARN_ON(!node_demotion);
#endif
mutex_lock(&memory_tier_lock);
/*
* For now we can have 4 faster memory tiers with smaller adistance
* than default DRAM tier.
*/
default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
if (!default_dram_type)
panic("%s() failed to allocate default DRAM tier\n", __func__);
/*
* Look at all the existing N_MEMORY nodes and add them to
* default memory tier or to a tier if we already have memory
* types assigned.
*/
for_each_node_state(node, N_MEMORY) {
memtier = set_node_memory_tier(node);
if (IS_ERR(memtier))
/*
* Continue with memtiers we are able to setup
*/
break;
}
establish_demotion_targets();
mutex_unlock(&memory_tier_lock);
hotplug_memory_notifier(memtier_hotplug_callback, MEMTIER_HOTPLUG_PRIO);
return 0;
}
subsys_initcall(memory_tier_init);
bool numa_demotion_enabled = false;
#ifdef CONFIG_MIGRATION
#ifdef CONFIG_SYSFS
static ssize_t numa_demotion_enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%s\n",
numa_demotion_enabled ? "true" : "false");
}
static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
ssize_t ret;
ret = kstrtobool(buf, &numa_demotion_enabled);
if (ret)
return ret;
return count;
}
static struct kobj_attribute numa_demotion_enabled_attr =
__ATTR(demotion_enabled, 0644, numa_demotion_enabled_show,
numa_demotion_enabled_store);
static struct attribute *numa_attrs[] = {
&numa_demotion_enabled_attr.attr,
NULL,
};
static const struct attribute_group numa_attr_group = {
.attrs = numa_attrs,
};
static int __init numa_init_sysfs(void)
{
int err;
struct kobject *numa_kobj;
numa_kobj = kobject_create_and_add("numa", mm_kobj);
if (!numa_kobj) {
pr_err("failed to create numa kobject\n");
return -ENOMEM;
}
err = sysfs_create_group(numa_kobj, &numa_attr_group);
if (err) {
pr_err("failed to register numa group\n");
goto delete_obj;
}
return 0;
delete_obj:
kobject_put(numa_kobj);
return err;
}
subsys_initcall(numa_init_sysfs);
#endif /* CONFIG_SYSFS */
#endif