[patch 073/163] mm: memcg/slab: use a single set of kmem_caches for all accounted allocations

Andrew Morton
2020-08-07T06:21:15Z

From: Roman Gushchin <guro@fb.com>
Subject: mm: memcg/slab: use a single set of kmem_caches for all accounted allocations

This is fairly big but mostly red patch, which makes all accounted slab
allocations use a single set of kmem_caches instead of creating a separate
set for each memory cgroup.

Because the number of non-root kmem_caches is now capped by the number of
root kmem_caches, there is no need to shrink or destroy them prematurely.
They can be perfectly destroyed together with their root counterparts.
This allows to dramatically simplify the management of non-root
kmem_caches and delete a ton of code.

This patch performs the following changes:
1) introduces memcg_params.memcg_cache pointer to represent the
kmem_cache which will be used for all non-root allocations
2) reuses the existing memcg kmem_cache creation mechanism
to create memcg kmem_cache on the first allocation attempt
3) memcg kmem_caches are named <kmemcache_name>-memcg,
e.g. dentry-memcg
4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache
or schedule it's creation and return the root cache
5) removes almost all non-root kmem_cache management code
(separate refcounter, reparenting, shrinking, etc)
6) makes slab debugfs to display root_mem_cgroup css id and never
show :dead and :deact flags in the memcg_slabinfo attribute.

Following patches in the series will simplify the kmem_cache creation.

Link: http://lkml.kernel.org/r/20200623174037.3951353-13-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/memcontrol.h | 5
include/linux/slab.h | 5
mm/memcontrol.c | 165 ++----------
mm/slab.c | 16 -
mm/slab.h | 146 +++--------
mm/slab_common.c | 461 +++--------------------------------
mm/slub.c | 38 --
7 files changed, 136 insertions(+), 700 deletions(-)

--- a/include/linux/memcontrol.h~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/include/linux/memcontrol.h
@@ -317,7 +317,6 @@ struct mem_cgroup {
/* Index in the kmem_cache->memcg_params.memcg_caches array */
int kmemcg_id;
enum memcg_kmem_state kmem_state;
- struct list_head kmem_caches;
struct obj_cgroup __rcu *objcg;
struct list_head objcg_list; /* list of inherited objcgs */
#endif
@@ -1404,9 +1403,7 @@ static inline void memcg_set_shrinker_bi
}
#endif

-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
- struct obj_cgroup **objcgp);
-void memcg_kmem_put_cache(struct kmem_cache *cachep);
+struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);

#ifdef CONFIG_MEMCG_KMEM
int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
--- a/include/linux/slab.h~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/include/linux/slab.h
@@ -155,8 +155,7 @@ struct kmem_cache *kmem_cache_create_use
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);

-void memcg_create_kmem_cache(struct mem_cgroup *, struct kmem_cache *);
-void memcg_deactivate_kmem_caches(struct mem_cgroup *, struct mem_cgroup *);
+void memcg_create_kmem_cache(struct kmem_cache *cachep);

/*
* Please use this macro to create slab caches. Simply specify the
@@ -580,8 +579,6 @@ static __always_inline void *kmalloc_nod
return __kmalloc_node(size, flags, node);
}

-int memcg_update_all_caches(int num_memcgs);
-
/**
* kmalloc_array - allocate memory for an array.
* @n: number of elements.
--- a/mm/memcontrol.c~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/mm/memcontrol.c
@@ -350,7 +350,7 @@ static void memcg_reparent_objcgs(struct
}

/*
- * This will be the memcg's index in each cache's ->memcg_params.memcg_caches.
+ * This will be used as a shrinker list's index.
* The main reason for not using cgroup id for this:
* this works better in sparse environments, where we have a lot of memcgs,
* but only a few kmem-limited. Or also, if we have, for instance, 200
@@ -569,20 +569,16 @@ ino_t page_cgroup_ino(struct page *page)
unsigned long ino = 0;

rcu_read_lock();
- if (PageSlab(page) && !PageTail(page)) {
- memcg = memcg_from_slab_page(page);
- } else {
- memcg = page->mem_cgroup;
+ memcg = page->mem_cgroup;

- /*
- * The lowest bit set means that memcg isn't a valid
- * memcg pointer, but a obj_cgroups pointer.
- * In this case the page is shared and doesn't belong
- * to any specific memory cgroup.
- */
- if ((unsigned long) memcg & 0x1UL)
- memcg = NULL;
- }
+ /*
+ * The lowest bit set means that memcg isn't a valid
+ * memcg pointer, but a obj_cgroups pointer.
+ * In this case the page is shared and doesn't belong
+ * to any specific memory cgroup.
+ */
+ if ((unsigned long) memcg & 0x1UL)
+ memcg = NULL;

while (memcg && !(memcg->css.flags & CSS_ONLINE))
memcg = parent_mem_cgroup(memcg);
@@ -2822,12 +2818,18 @@ struct mem_cgroup *mem_cgroup_from_obj(v
page = virt_to_head_page(p);

/*
- * Slab pages don't have page->mem_cgroup set because corresponding
- * kmem caches can be reparented during the lifetime. That's why
- * memcg_from_slab_page() should be used instead.
- */
- if (PageSlab(page))
- return memcg_from_slab_page(page);
+ * Slab objects are accounted individually, not per-page.
+ * Memcg membership data for each individual object is saved in
+ * the page->obj_cgroups.
+ */
+ if (page_has_obj_cgroups(page)) {
+ struct obj_cgroup *objcg;
+ unsigned int off;
+
+ off = obj_to_index(page->slab_cache, page, p);
+ objcg = page_obj_cgroups(page)[off];
+ return obj_cgroup_memcg(objcg);
+ }

/* All other pages use page->mem_cgroup */
return page->mem_cgroup;
@@ -2882,9 +2884,7 @@ static int memcg_alloc_cache_id(void)
else if (size > MEMCG_CACHES_MAX_SIZE)
size = MEMCG_CACHES_MAX_SIZE;

- err = memcg_update_all_caches(size);
- if (!err)
- err = memcg_update_all_list_lrus(size);
+ err = memcg_update_all_list_lrus(size);
if (!err)
memcg_nr_cache_ids = size;

@@ -2903,7 +2903,6 @@ static void memcg_free_cache_id(int id)
}

struct memcg_kmem_cache_create_work {
- struct mem_cgroup *memcg;
struct kmem_cache *cachep;
struct work_struct work;
};
@@ -2912,33 +2911,24 @@ static void memcg_kmem_cache_create_func
{
struct memcg_kmem_cache_create_work *cw =
container_of(w, struct memcg_kmem_cache_create_work, work);
- struct mem_cgroup *memcg = cw->memcg;
struct kmem_cache *cachep = cw->cachep;

- memcg_create_kmem_cache(memcg, cachep);
+ memcg_create_kmem_cache(cachep);

- css_put(&memcg->css);
kfree(cw);
}

/*
* Enqueue the creation of a per-memcg kmem_cache.
*/
-static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
- struct kmem_cache *cachep)
+static void memcg_schedule_kmem_cache_create(struct kmem_cache *cachep)
{
struct memcg_kmem_cache_create_work *cw;

- if (!css_tryget_online(&memcg->css))
- return;
-
cw = kmalloc(sizeof(*cw), GFP_NOWAIT | __GFP_NOWARN);
- if (!cw) {
- css_put(&memcg->css);
+ if (!cw)
return;
- }

- cw->memcg = memcg;
cw->cachep = cachep;
INIT_WORK(&cw->work, memcg_kmem_cache_create_func);

@@ -2946,102 +2936,26 @@ static void memcg_schedule_kmem_cache_cr
}

/**
- * memcg_kmem_get_cache: select the correct per-memcg cache for allocation
+ * memcg_kmem_get_cache: select memcg or root cache for allocation
* @cachep: the original global kmem cache
*
* Return the kmem_cache we're supposed to use for a slab allocation.
- * We try to use the current memcg's version of the cache.
*
* If the cache does not exist yet, if we are the first user of it, we
* create it asynchronously in a workqueue and let the current allocation
* go through with the original cache.
- *
- * This function takes a reference to the cache it returns to assure it
- * won't get destroyed while we are working with it. Once the caller is
- * done with it, memcg_kmem_put_cache() must be called to release the
- * reference.
*/
-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
- struct obj_cgroup **objcgp)
+struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
{
- struct mem_cgroup *memcg;
struct kmem_cache *memcg_cachep;
- struct memcg_cache_array *arr;
- int kmemcg_id;
-
- VM_BUG_ON(!is_root_cache(cachep));

- if (memcg_kmem_bypass())
+ memcg_cachep = READ_ONCE(cachep->memcg_params.memcg_cache);
+ if (unlikely(!memcg_cachep)) {
+ memcg_schedule_kmem_cache_create(cachep);
return cachep;
-
- rcu_read_lock();
-
- if (unlikely(current->active_memcg))
- memcg = current->active_memcg;
- else
- memcg = mem_cgroup_from_task(current);
-
- if (!memcg || memcg == root_mem_cgroup)
- goto out_unlock;
-
- kmemcg_id = READ_ONCE(memcg->kmemcg_id);
- if (kmemcg_id < 0)
- goto out_unlock;
-
- arr = rcu_dereference(cachep->memcg_params.memcg_caches);
-
- /*
- * Make sure we will access the up-to-date value. The code updating
- * memcg_caches issues a write barrier to match the data dependency
- * barrier inside READ_ONCE() (see memcg_create_kmem_cache()).
- */
- memcg_cachep = READ_ONCE(arr->entries[kmemcg_id]);
-
- /*
- * If we are in a safe context (can wait, and not in interrupt
- * context), we could be be predictable and return right away.
- * This would guarantee that the allocation being performed
- * already belongs in the new cache.
- *
- * However, there are some clashes that can arrive from locking.
- * For instance, because we acquire the slab_mutex while doing
- * memcg_create_kmem_cache, this means no further allocation
- * could happen with the slab_mutex held. So it's better to
- * defer everything.
- *
- * If the memcg is dying or memcg_cache is about to be released,
- * don't bother creating new kmem_caches. Because memcg_cachep
- * is ZEROed as the fist step of kmem offlining, we don't need
- * percpu_ref_tryget_live() here. css_tryget_online() check in
- * memcg_schedule_kmem_cache_create() will prevent us from
- * creation of a new kmem_cache.
- */
- if (unlikely(!memcg_cachep))
- memcg_schedule_kmem_cache_create(memcg, cachep);
- else if (percpu_ref_tryget(&memcg_cachep->memcg_params.refcnt)) {
- struct obj_cgroup *objcg = rcu_dereference(memcg->objcg);
-
- if (!objcg || !obj_cgroup_tryget(objcg)) {
- percpu_ref_put(&memcg_cachep->memcg_params.refcnt);
- goto out_unlock;
- }
-
- *objcgp = objcg;
- cachep = memcg_cachep;
}
-out_unlock:
- rcu_read_unlock();
- return cachep;
-}

-/**
- * memcg_kmem_put_cache: drop reference taken by memcg_kmem_get_cache
- * @cachep: the cache returned by memcg_kmem_get_cache
- */
-void memcg_kmem_put_cache(struct kmem_cache *cachep)
-{
- if (!is_root_cache(cachep))
- percpu_ref_put(&cachep->memcg_params.refcnt);
+ return memcg_cachep;
}

/**
@@ -3731,7 +3645,6 @@ static int memcg_online_kmem(struct mem_
*/
memcg->kmemcg_id = memcg_id;
memcg->kmem_state = KMEM_ONLINE;
- INIT_LIST_HEAD(&memcg->kmem_caches);

return 0;
}
@@ -3744,22 +3657,13 @@ static void memcg_offline_kmem(struct me

if (memcg->kmem_state != KMEM_ONLINE)
return;
- /*
- * Clear the online state before clearing memcg_caches array
- * entries. The slab_mutex in memcg_deactivate_kmem_caches()
- * guarantees that no cache will be created for this cgroup
- * after we are done (see memcg_create_kmem_cache()).
- */
+
memcg->kmem_state = KMEM_ALLOCATED;

parent = parent_mem_cgroup(memcg);
if (!parent)
parent = root_mem_cgroup;

- /*
- * Deactivate and reparent kmem_caches and objcgs.
- */
- memcg_deactivate_kmem_caches(memcg, parent);
memcg_reparent_objcgs(memcg, parent);

kmemcg_id = memcg->kmemcg_id;
@@ -5384,9 +5288,6 @@ mem_cgroup_css_alloc(struct cgroup_subsy

/* The following stuff does not apply to the root */
if (!parent) {
-#ifdef CONFIG_MEMCG_KMEM
- INIT_LIST_HEAD(&memcg->kmem_caches);
-#endif
root_mem_cgroup = memcg;
return &memcg->css;
}
--- a/mm/slab.c~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/mm/slab.c
@@ -1249,7 +1249,7 @@ void __init kmem_cache_init(void)
nr_node_ids * sizeof(struct kmem_cache_node *),
SLAB_HWCACHE_ALIGN, 0, 0);
list_add(&kmem_cache->list, &slab_caches);
- memcg_link_cache(kmem_cache, NULL);
+ memcg_link_cache(kmem_cache);
slab_state = PARTIAL;

/*
@@ -2253,17 +2253,6 @@ int __kmem_cache_shrink(struct kmem_cach
return (ret ? 1 : 0);
}

-#ifdef CONFIG_MEMCG
-void __kmemcg_cache_deactivate(struct kmem_cache *cachep)
-{
- __kmem_cache_shrink(cachep);
-}
-
-void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
-{
-}
-#endif
-
int __kmem_cache_shutdown(struct kmem_cache *cachep)
{
return __kmem_cache_shrink(cachep);
@@ -3872,7 +3861,8 @@ static int do_tune_cpucache(struct kmem_
return ret;

lockdep_assert_held(&slab_mutex);
- for_each_memcg_cache(c, cachep) {
+ c = memcg_cache(cachep);
+ if (c) {
/* return value determined by the root cache only */
__do_tune_cpucache(c, limit, batchcount, shared, gfp);
}
--- a/mm/slab_common.c~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/mm/slab_common.c
@@ -133,141 +133,36 @@ int __kmem_cache_alloc_bulk(struct kmem_
#ifdef CONFIG_MEMCG_KMEM

LIST_HEAD(slab_root_caches);
-static DEFINE_SPINLOCK(memcg_kmem_wq_lock);
-
-static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref);

void slab_init_memcg_params(struct kmem_cache *s)
{
s->memcg_params.root_cache = NULL;
- RCU_INIT_POINTER(s->memcg_params.memcg_caches, NULL);
- INIT_LIST_HEAD(&s->memcg_params.children);
- s->memcg_params.dying = false;
-}
-
-static int init_memcg_params(struct kmem_cache *s,
- struct kmem_cache *root_cache)
-{
- struct memcg_cache_array *arr;
-
- if (root_cache) {
- int ret = percpu_ref_init(&s->memcg_params.refcnt,
- kmemcg_cache_shutdown,
- 0, GFP_KERNEL);
- if (ret)
- return ret;
-
- s->memcg_params.root_cache = root_cache;
- INIT_LIST_HEAD(&s->memcg_params.children_node);
- INIT_LIST_HEAD(&s->memcg_params.kmem_caches_node);
- return 0;
- }
-
- slab_init_memcg_params(s);
-
- if (!memcg_nr_cache_ids)
- return 0;
-
- arr = kvzalloc(sizeof(struct memcg_cache_array) +
- memcg_nr_cache_ids * sizeof(void *),
- GFP_KERNEL);
- if (!arr)
- return -ENOMEM;
-
- RCU_INIT_POINTER(s->memcg_params.memcg_caches, arr);
- return 0;
-}
-
-static void destroy_memcg_params(struct kmem_cache *s)
-{
- if (is_root_cache(s)) {
- kvfree(rcu_access_pointer(s->memcg_params.memcg_caches));
- } else {
- mem_cgroup_put(s->memcg_params.memcg);
- WRITE_ONCE(s->memcg_params.memcg, NULL);
- percpu_ref_exit(&s->memcg_params.refcnt);
- }
+ s->memcg_params.memcg_cache = NULL;
}

-static void free_memcg_params(struct rcu_head *rcu)
+static void init_memcg_params(struct kmem_cache *s,
+ struct kmem_cache *root_cache)
{
- struct memcg_cache_array *old;
-
- old = container_of(rcu, struct memcg_cache_array, rcu);
- kvfree(old);
-}
-
-static int update_memcg_params(struct kmem_cache *s, int new_array_size)
-{
- struct memcg_cache_array *old, *new;
-
- new = kvzalloc(sizeof(struct memcg_cache_array) +
- new_array_size * sizeof(void *), GFP_KERNEL);
- if (!new)
- return -ENOMEM;
-
- old = rcu_dereference_protected(s->memcg_params.memcg_caches,
- lockdep_is_held(&slab_mutex));
- if (old)
- memcpy(new->entries, old->entries,
- memcg_nr_cache_ids * sizeof(void *));
-
- rcu_assign_pointer(s->memcg_params.memcg_caches, new);
- if (old)
- call_rcu(&old->rcu, free_memcg_params);
- return 0;
-}
-
-int memcg_update_all_caches(int num_memcgs)
-{
- struct kmem_cache *s;
- int ret = 0;
-
- mutex_lock(&slab_mutex);
- list_for_each_entry(s, &slab_root_caches, root_caches_node) {
- ret = update_memcg_params(s, num_memcgs);
- /*
- * Instead of freeing the memory, we'll just leave the caches
- * up to this point in an updated state.
- */
- if (ret)
- break;
- }
- mutex_unlock(&slab_mutex);
- return ret;
+ if (root_cache)
+ s->memcg_params.root_cache = root_cache;
+ else
+ slab_init_memcg_params(s);
}

-void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg)
+void memcg_link_cache(struct kmem_cache *s)
{
- if (is_root_cache(s)) {
+ if (is_root_cache(s))
list_add(&s->root_caches_node, &slab_root_caches);
- } else {
- css_get(&memcg->css);
- s->memcg_params.memcg = memcg;
- list_add(&s->memcg_params.children_node,
- &s->memcg_params.root_cache->memcg_params.children);
- list_add(&s->memcg_params.kmem_caches_node,
- &s->memcg_params.memcg->kmem_caches);
- }
}

static void memcg_unlink_cache(struct kmem_cache *s)
{
- if (is_root_cache(s)) {
+ if (is_root_cache(s))
list_del(&s->root_caches_node);
- } else {
- list_del(&s->memcg_params.children_node);
- list_del(&s->memcg_params.kmem_caches_node);
- }
}
#else
-static inline int init_memcg_params(struct kmem_cache *s,
- struct kmem_cache *root_cache)
-{
- return 0;
-}
-
-static inline void destroy_memcg_params(struct kmem_cache *s)
+static inline void init_memcg_params(struct kmem_cache *s,
+ struct kmem_cache *root_cache)
{
}

@@ -328,14 +223,6 @@ int slab_unmergeable(struct kmem_cache *
if (s->refcount < 0)
return 1;

-#ifdef CONFIG_MEMCG_KMEM
- /*
- * Skip the dying kmem_cache.
- */
- if (s->memcg_params.dying)
- return 1;
-#endif
-
return 0;
}

@@ -390,7 +277,7 @@ static struct kmem_cache *create_cache(c
unsigned int object_size, unsigned int align,
slab_flags_t flags, unsigned int useroffset,
unsigned int usersize, void (*ctor)(void *),
- struct mem_cgroup *memcg, struct kmem_cache *root_cache)
+ struct kmem_cache *root_cache)
{
struct kmem_cache *s;
int err;
@@ -410,24 +297,20 @@ static struct kmem_cache *create_cache(c
s->useroffset = useroffset;
s->usersize = usersize;

- err = init_memcg_params(s, root_cache);
- if (err)
- goto out_free_cache;
-
+ init_memcg_params(s, root_cache);
err = __kmem_cache_create(s, flags);
if (err)
goto out_free_cache;

s->refcount = 1;
list_add(&s->list, &slab_caches);
- memcg_link_cache(s, memcg);
+ memcg_link_cache(s);
out:
if (err)
return ERR_PTR(err);
return s;

out_free_cache:
- destroy_memcg_params(s);
kmem_cache_free(kmem_cache, s);
goto out;
}
@@ -514,7 +397,7 @@ kmem_cache_create_usercopy(const char *n

s = create_cache(cache_name, size,
calculate_alignment(flags, align, size),
- flags, useroffset, usersize, ctor, NULL, NULL);
+ flags, useroffset, usersize, ctor, NULL);
if (IS_ERR(s)) {
err = PTR_ERR(s);
kfree_const(cache_name);
@@ -639,51 +522,27 @@ static int shutdown_cache(struct kmem_ca

#ifdef CONFIG_MEMCG_KMEM
/*
- * memcg_create_kmem_cache - Create a cache for a memory cgroup.
- * @memcg: The memory cgroup the new cache is for.
+ * memcg_create_kmem_cache - Create a cache for non-root memory cgroups.
* @root_cache: The parent of the new cache.
*
* This function attempts to create a kmem cache that will serve allocation
- * requests going from @memcg to @root_cache. The new cache inherits properties
- * from its parent.
+ * requests going all non-root memory cgroups to @root_cache. The new cache
+ * inherits properties from its parent.
*/
-void memcg_create_kmem_cache(struct mem_cgroup *memcg,
- struct kmem_cache *root_cache)
+void memcg_create_kmem_cache(struct kmem_cache *root_cache)
{
- static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */
- struct cgroup_subsys_state *css = &memcg->css;
- struct memcg_cache_array *arr;
struct kmem_cache *s = NULL;
char *cache_name;
- int idx;

get_online_cpus();
get_online_mems();

mutex_lock(&slab_mutex);

- /*
- * The memory cgroup could have been offlined while the cache
- * creation work was pending.
- */
- if (memcg->kmem_state != KMEM_ONLINE)
+ if (root_cache->memcg_params.memcg_cache)
goto out_unlock;

- idx = memcg_cache_id(memcg);
- arr = rcu_dereference_protected(root_cache->memcg_params.memcg_caches,
- lockdep_is_held(&slab_mutex));
-
- /*
- * Since per-memcg caches are created asynchronously on first
- * allocation (see memcg_kmem_get_cache()), several threads can try to
- * create the same cache, but only one of them may succeed.
- */
- if (arr->entries[idx])
- goto out_unlock;
-
- cgroup_name(css->cgroup, memcg_name_buf, sizeof(memcg_name_buf));
- cache_name = kasprintf(GFP_KERNEL, "%s(%llu:%s)", root_cache->name,
- css->serial_nr, memcg_name_buf);
+ cache_name = kasprintf(GFP_KERNEL, "%s-memcg", root_cache->name);
if (!cache_name)
goto out_unlock;

@@ -691,7 +550,7 @@ void memcg_create_kmem_cache(struct mem_
root_cache->align,
root_cache->flags & CACHE_CREATE_MASK,
root_cache->useroffset, root_cache->usersize,
- root_cache->ctor, memcg, root_cache);
+ root_cache->ctor, root_cache);
/*
* If we could not create a memcg cache, do not complain, because
* that's not critical at all as we can always proceed with the root
@@ -708,7 +567,7 @@ void memcg_create_kmem_cache(struct mem_
* initialized.
*/
smp_wmb();
- arr->entries[idx] = s;
+ root_cache->memcg_params.memcg_cache = s;

out_unlock:
mutex_unlock(&slab_mutex);
@@ -717,231 +576,40 @@ out_unlock:
put_online_cpus();
}

-static void kmemcg_workfn(struct work_struct *work)
-{
- struct kmem_cache *s = container_of(work, struct kmem_cache,
- memcg_params.work);
-
- get_online_cpus();
- get_online_mems();
-
- mutex_lock(&slab_mutex);
- s->memcg_params.work_fn(s);
- mutex_unlock(&slab_mutex);
-
- put_online_mems();
- put_online_cpus();
-}
-
-static void kmemcg_rcufn(struct rcu_head *head)
-{
- struct kmem_cache *s = container_of(head, struct kmem_cache,
- memcg_params.rcu_head);
-
- /*
- * We need to grab blocking locks. Bounce to ->work. The
- * work item shares the space with the RCU head and can't be
- * initialized earlier.
- */
- INIT_WORK(&s->memcg_params.work, kmemcg_workfn);
- queue_work(memcg_kmem_cache_wq, &s->memcg_params.work);
-}
-
-static void kmemcg_cache_shutdown_fn(struct kmem_cache *s)
-{
- WARN_ON(shutdown_cache(s));
-}
-
-static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref)
-{
- struct kmem_cache *s = container_of(percpu_ref, struct kmem_cache,
- memcg_params.refcnt);
- unsigned long flags;
-
- spin_lock_irqsave(&memcg_kmem_wq_lock, flags);
- if (s->memcg_params.root_cache->memcg_params.dying)
- goto unlock;
-
- s->memcg_params.work_fn = kmemcg_cache_shutdown_fn;
- INIT_WORK(&s->memcg_params.work, kmemcg_workfn);
- queue_work(memcg_kmem_cache_wq, &s->memcg_params.work);
-
-unlock:
- spin_unlock_irqrestore(&memcg_kmem_wq_lock, flags);
-}
-
-static void kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
-{
- __kmemcg_cache_deactivate_after_rcu(s);
- percpu_ref_kill(&s->memcg_params.refcnt);
-}
-
-static void kmemcg_cache_deactivate(struct kmem_cache *s)
-{
- if (WARN_ON_ONCE(is_root_cache(s)))
- return;
-
- __kmemcg_cache_deactivate(s);
- s->flags |= SLAB_DEACTIVATED;
-
- /*
- * memcg_kmem_wq_lock is used to synchronize memcg_params.dying
- * flag and make sure that no new kmem_cache deactivation tasks
- * are queued (see flush_memcg_workqueue() ).
- */
- spin_lock_irq(&memcg_kmem_wq_lock);
- if (s->memcg_params.root_cache->memcg_params.dying)
- goto unlock;
-
- s->memcg_params.work_fn = kmemcg_cache_deactivate_after_rcu;
- call_rcu(&s->memcg_params.rcu_head, kmemcg_rcufn);
-unlock:
- spin_unlock_irq(&memcg_kmem_wq_lock);
-}
-
-void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg,
- struct mem_cgroup *parent)
-{
- int idx;
- struct memcg_cache_array *arr;
- struct kmem_cache *s, *c;
- unsigned int nr_reparented;
-
- idx = memcg_cache_id(memcg);
-
- get_online_cpus();
- get_online_mems();
-
- mutex_lock(&slab_mutex);
- list_for_each_entry(s, &slab_root_caches, root_caches_node) {
- arr = rcu_dereference_protected(s->memcg_params.memcg_caches,
- lockdep_is_held(&slab_mutex));
- c = arr->entries[idx];
- if (!c)
- continue;
-
- kmemcg_cache_deactivate(c);
- arr->entries[idx] = NULL;
- }
- nr_reparented = 0;
- list_for_each_entry(s, &memcg->kmem_caches,
- memcg_params.kmem_caches_node) {
- WRITE_ONCE(s->memcg_params.memcg, parent);
- css_put(&memcg->css);
- nr_reparented++;
- }
- if (nr_reparented) {
- list_splice_init(&memcg->kmem_caches,
- &parent->kmem_caches);
- css_get_many(&parent->css, nr_reparented);
- }
- mutex_unlock(&slab_mutex);
-
- put_online_mems();
- put_online_cpus();
-}
-
static int shutdown_memcg_caches(struct kmem_cache *s)
{
- struct memcg_cache_array *arr;
- struct kmem_cache *c, *c2;
- LIST_HEAD(busy);
- int i;
-
BUG_ON(!is_root_cache(s));

- /*
- * First, shutdown active caches, i.e. caches that belong to online
- * memory cgroups.
- */
- arr = rcu_dereference_protected(s->memcg_params.memcg_caches,
- lockdep_is_held(&slab_mutex));
- for_each_memcg_cache_index(i) {
- c = arr->entries[i];
- if (!c)
- continue;
- if (shutdown_cache(c))
- /*
- * The cache still has objects. Move it to a temporary
- * list so as not to try to destroy it for a second
- * time while iterating over inactive caches below.
- */
- list_move(&c->memcg_params.children_node, &busy);
- else
- /*
- * The cache is empty and will be destroyed soon. Clear
- * the pointer to it in the memcg_caches array so that
- * it will never be accessed even if the root cache
- * stays alive.
- */
- arr->entries[i] = NULL;
- }
-
- /*
- * Second, shutdown all caches left from memory cgroups that are now
- * offline.
- */
- list_for_each_entry_safe(c, c2, &s->memcg_params.children,
- memcg_params.children_node)
- shutdown_cache(c);
-
- list_splice(&busy, &s->memcg_params.children);
+ if (s->memcg_params.memcg_cache)
+ WARN_ON(shutdown_cache(s->memcg_params.memcg_cache));

- /*
- * A cache being destroyed must be empty. In particular, this means
- * that all per memcg caches attached to it must be empty too.
- */
- if (!list_empty(&s->memcg_params.children))
- return -EBUSY;
return 0;
}

-static void memcg_set_kmem_cache_dying(struct kmem_cache *s)
-{
- spin_lock_irq(&memcg_kmem_wq_lock);
- s->memcg_params.dying = true;
- spin_unlock_irq(&memcg_kmem_wq_lock);
-}
-
static void flush_memcg_workqueue(struct kmem_cache *s)
{
/*
- * SLAB and SLUB deactivate the kmem_caches through call_rcu. Make
- * sure all registered rcu callbacks have been invoked.
- */
- rcu_barrier();
-
- /*
* SLAB and SLUB create memcg kmem_caches through workqueue and SLUB
* deactivates the memcg kmem_caches through workqueue. Make sure all
* previous workitems on workqueue are processed.
*/
if (likely(memcg_kmem_cache_wq))
flush_workqueue(memcg_kmem_cache_wq);
-
- /*
- * If we're racing with children kmem_cache deactivation, it might
- * take another rcu grace period to complete their destruction.
- * At this moment the corresponding percpu_ref_kill() call should be
- * done, but it might take another rcu grace period to complete
- * switching to the atomic mode.
- * Please, note that we check without grabbing the slab_mutex. It's safe
- * because at this moment the children list can't grow.
- */
- if (!list_empty(&s->memcg_params.children))
- rcu_barrier();
}
#else
static inline int shutdown_memcg_caches(struct kmem_cache *s)
{
return 0;
}
+
+static inline void flush_memcg_workqueue(struct kmem_cache *s)
+{
+}
#endif /* CONFIG_MEMCG_KMEM */

void slab_kmem_cache_release(struct kmem_cache *s)
{
__kmem_cache_release(s);
- destroy_memcg_params(s);
kfree_const(s->name);
kmem_cache_free(kmem_cache, s);
}
@@ -953,6 +621,8 @@ void kmem_cache_destroy(struct kmem_cach
if (unlikely(!s))
return;

+ flush_memcg_workqueue(s);
+
get_online_cpus();
get_online_mems();

@@ -962,22 +632,6 @@ void kmem_cache_destroy(struct kmem_cach
if (s->refcount)
goto out_unlock;

-#ifdef CONFIG_MEMCG_KMEM
- memcg_set_kmem_cache_dying(s);
-
- mutex_unlock(&slab_mutex);
-
- put_online_mems();
- put_online_cpus();
-
- flush_memcg_workqueue(s);
-
- get_online_cpus();
- get_online_mems();
-
- mutex_lock(&slab_mutex);
-#endif
-
err = shutdown_memcg_caches(s);
if (!err)
err = shutdown_cache(s);
@@ -1019,7 +673,7 @@ int kmem_cache_shrink(struct kmem_cache
EXPORT_SYMBOL(kmem_cache_shrink);

/**
- * kmem_cache_shrink_all - shrink a cache and all memcg caches for root cache
+ * kmem_cache_shrink_all - shrink root and memcg caches
* @s: The cache pointer
*/
void kmem_cache_shrink_all(struct kmem_cache *s)
@@ -1036,21 +690,11 @@ void kmem_cache_shrink_all(struct kmem_c
kasan_cache_shrink(s);
__kmem_cache_shrink(s);

- /*
- * We have to take the slab_mutex to protect from the memcg list
- * modification.
- */
- mutex_lock(&slab_mutex);
- for_each_memcg_cache(c, s) {
- /*
- * Don't need to shrink deactivated memcg caches.
- */
- if (s->flags & SLAB_DEACTIVATED)
- continue;
+ c = memcg_cache(s);
+ if (c) {
kasan_cache_shrink(c);
__kmem_cache_shrink(c);
}
- mutex_unlock(&slab_mutex);
put_online_mems();
put_online_cpus();
}
@@ -1105,7 +749,7 @@ struct kmem_cache *__init create_kmalloc

create_boot_cache(s, name, size, flags, useroffset, usersize);
list_add(&s->list, &slab_caches);
- memcg_link_cache(s, NULL);
+ memcg_link_cache(s);
s->refcount = 1;
return s;
}
@@ -1483,7 +1127,8 @@ memcg_accumulate_slabinfo(struct kmem_ca
if (!is_root_cache(s))
return;

- for_each_memcg_cache(c, s) {
+ c = memcg_cache(s);
+ if (c) {
memset(&sinfo, 0, sizeof(sinfo));
get_slabinfo(c, &sinfo);

@@ -1614,7 +1259,7 @@ module_init(slab_proc_init);

#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_MEMCG_KMEM)
/*
- * Display information about kmem caches that have child memcg caches.
+ * Display information about kmem caches that have memcg cache.
*/
static int memcg_slabinfo_show(struct seq_file *m, void *unused)
{
@@ -1626,9 +1271,9 @@ static int memcg_slabinfo_show(struct se
seq_puts(m, " <active_slabs> <num_slabs>\n");
list_for_each_entry(s, &slab_root_caches, root_caches_node) {
/*
- * Skip kmem caches that don't have any memcg children.
+ * Skip kmem caches that don't have the memcg cache.
*/
- if (list_empty(&s->memcg_params.children))
+ if (!s->memcg_params.memcg_cache)
continue;

memset(&sinfo, 0, sizeof(sinfo));
@@ -1637,23 +1282,13 @@ static int memcg_slabinfo_show(struct se
cache_name(s), sinfo.active_objs, sinfo.num_objs,
sinfo.active_slabs, sinfo.num_slabs);

- for_each_memcg_cache(c, s) {
- struct cgroup_subsys_state *css;
- char *status = "";
-
- css = &c->memcg_params.memcg->css;
- if (!(css->flags & CSS_ONLINE))
- status = ":dead";
- else if (c->flags & SLAB_DEACTIVATED)
- status = ":deact";
-
- memset(&sinfo, 0, sizeof(sinfo));
- get_slabinfo(c, &sinfo);
- seq_printf(m, "%-17s %4d%-6s %6lu %6lu %6lu %6lu\n",
- cache_name(c), css->id, status,
- sinfo.active_objs, sinfo.num_objs,
- sinfo.active_slabs, sinfo.num_slabs);
- }
+ c = s->memcg_params.memcg_cache;
+ memset(&sinfo, 0, sizeof(sinfo));
+ get_slabinfo(c, &sinfo);
+ seq_printf(m, "%-17s %4d %6lu %6lu %6lu %6lu\n",
+ cache_name(c), root_mem_cgroup->css.id,
+ sinfo.active_objs, sinfo.num_objs,
+ sinfo.active_slabs, sinfo.num_slabs);
}
mutex_unlock(&slab_mutex);
return 0;
--- a/mm/slab.h~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/mm/slab.h
@@ -32,66 +32,25 @@ struct kmem_cache {

#else /* !CONFIG_SLOB */

-struct memcg_cache_array {
- struct rcu_head rcu;
- struct kmem_cache *entries[0];
-};
-
/*
* This is the main placeholder for memcg-related information in kmem caches.
- * Both the root cache and the child caches will have it. For the root cache,
- * this will hold a dynamically allocated array large enough to hold
- * information about the currently limited memcgs in the system. To allow the
- * array to be accessed without taking any locks, on relocation we free the old
- * version only after a grace period.
- *
- * Root and child caches hold different metadata.
+ * Both the root cache and the child cache will have it. Some fields are used
+ * in both cases, other are specific to root caches.
*
* @root_cache: Common to root and child caches. NULL for root, pointer to
* the root cache for children.
*
* The following fields are specific to root caches.
*
- * @memcg_caches: kmemcg ID indexed table of child caches. This table is
- * used to index child cachces during allocation and cleared
- * early during shutdown.
- *
- * @root_caches_node: List node for slab_root_caches list.
- *
- * @children: List of all child caches. While the child caches are also
- * reachable through @memcg_caches, a child cache remains on
- * this list until it is actually destroyed.
- *
- * The following fields are specific to child caches.
- *
- * @memcg: Pointer to the memcg this cache belongs to.
- *
- * @children_node: List node for @root_cache->children list.
- *
- * @kmem_caches_node: List node for @memcg->kmem_caches list.
+ * @memcg_cache: pointer to memcg kmem cache, used by all non-root memory
+ * cgroups.
+ * @root_caches_node: list node for slab_root_caches list.
*/
struct memcg_cache_params {
struct kmem_cache *root_cache;
- union {
- struct {
- struct memcg_cache_array __rcu *memcg_caches;
- struct list_head __root_caches_node;
- struct list_head children;
- bool dying;
- };
- struct {
- struct mem_cgroup *memcg;
- struct list_head children_node;
- struct list_head kmem_caches_node;
- struct percpu_ref refcnt;
-
- void (*work_fn)(struct kmem_cache *);
- union {
- struct rcu_head rcu_head;
- struct work_struct work;
- };
- };
- };
+
+ struct kmem_cache *memcg_cache;
+ struct list_head __root_caches_node;
};
#endif /* CONFIG_SLOB */

@@ -236,8 +195,6 @@ bool __kmem_cache_empty(struct kmem_cach
int __kmem_cache_shutdown(struct kmem_cache *);
void __kmem_cache_release(struct kmem_cache *);
int __kmem_cache_shrink(struct kmem_cache *);
-void __kmemcg_cache_deactivate(struct kmem_cache *s);
-void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s);
void slab_kmem_cache_release(struct kmem_cache *);
void kmem_cache_shrink_all(struct kmem_cache *s);

@@ -311,14 +268,6 @@ static inline bool kmem_cache_debug_flag
extern struct list_head slab_root_caches;
#define root_caches_node memcg_params.__root_caches_node

-/*
- * Iterate over all memcg caches of the given root cache. The caller must hold
- * slab_mutex.
- */
-#define for_each_memcg_cache(iter, root) \
- list_for_each_entry(iter, &(root)->memcg_params.children, \
- memcg_params.children_node)
-
static inline bool is_root_cache(struct kmem_cache *s)
{
return !s->memcg_params.root_cache;
@@ -349,6 +298,13 @@ static inline struct kmem_cache *memcg_r
return s->memcg_params.root_cache;
}

+static inline struct kmem_cache *memcg_cache(struct kmem_cache *s)
+{
+ if (is_root_cache(s))
+ return s->memcg_params.memcg_cache;
+ return NULL;
+}
+
static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
{
/*
@@ -361,25 +317,9 @@ static inline struct obj_cgroup **page_o
((unsigned long)page->obj_cgroups & ~0x1UL);
}

-/*
- * Expects a pointer to a slab page. Please note, that PageSlab() check
- * isn't sufficient, as it returns true also for tail compound slab pages,
- * which do not have slab_cache pointer set.
- * So this function assumes that the page can pass PageSlab() && !PageTail()
- * check.
- *
- * The kmem_cache can be reparented asynchronously. The caller must ensure
- * the memcg lifetime, e.g. by taking rcu_read_lock() or cgroup_mutex.
- */
-static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
+static inline bool page_has_obj_cgroups(struct page *page)
{
- struct kmem_cache *s;
-
- s = READ_ONCE(page->slab_cache);
- if (s && !is_root_cache(s))
- return READ_ONCE(s->memcg_params.memcg);
-
- return NULL;
+ return ((unsigned long)page->obj_cgroups & 0x1UL);
}

static inline int memcg_alloc_page_obj_cgroups(struct page *page,
@@ -418,17 +358,25 @@ static inline struct kmem_cache *memcg_s
size_t objects, gfp_t flags)
{
struct kmem_cache *cachep;
+ struct obj_cgroup *objcg;
+
+ if (memcg_kmem_bypass())
+ return s;

- cachep = memcg_kmem_get_cache(s, objcgp);
+ cachep = memcg_kmem_get_cache(s);
if (is_root_cache(cachep))
return s;

- if (obj_cgroup_charge(*objcgp, flags, objects * obj_full_size(s))) {
- obj_cgroup_put(*objcgp);
- memcg_kmem_put_cache(cachep);
+ objcg = get_obj_cgroup_from_current();
+ if (!objcg)
+ return s;
+
+ if (obj_cgroup_charge(objcg, flags, objects * obj_full_size(s))) {
+ obj_cgroup_put(objcg);
cachep = NULL;
}

+ *objcgp = objcg;
return cachep;
}

@@ -467,7 +415,6 @@ static inline void memcg_slab_post_alloc
}
}
obj_cgroup_put(objcg);
- memcg_kmem_put_cache(s);
}

static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
@@ -491,7 +438,7 @@ static inline void memcg_slab_free_hook(
}

extern void slab_init_memcg_params(struct kmem_cache *);
-extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
+extern void memcg_link_cache(struct kmem_cache *s);

#else /* CONFIG_MEMCG_KMEM */

@@ -499,9 +446,6 @@ extern void memcg_link_cache(struct kmem
#define slab_root_caches slab_caches
#define root_caches_node list

-#define for_each_memcg_cache(iter, root) \
- for ((void)(iter), (void)(root); 0; )
-
static inline bool is_root_cache(struct kmem_cache *s)
{
return true;
@@ -523,7 +467,17 @@ static inline struct kmem_cache *memcg_r
return s;
}

-static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
+static inline struct kmem_cache *memcg_cache(struct kmem_cache *s)
+{
+ return NULL;
+}
+
+static inline bool page_has_obj_cgroups(struct page *page)
+{
+ return false;
+}
+
+static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr)
{
return NULL;
}
@@ -560,8 +514,7 @@ static inline void slab_init_memcg_param
{
}

-static inline void memcg_link_cache(struct kmem_cache *s,
- struct mem_cgroup *memcg)
+static inline void memcg_link_cache(struct kmem_cache *s)
{
}

@@ -582,17 +535,14 @@ static __always_inline int charge_slab_p
gfp_t gfp, int order,
struct kmem_cache *s)
{
-#ifdef CONFIG_MEMCG_KMEM
if (memcg_kmem_enabled() && !is_root_cache(s)) {
int ret;

ret = memcg_alloc_page_obj_cgroups(page, s, gfp);
if (ret)
return ret;
-
- percpu_ref_get_many(&s->memcg_params.refcnt, 1 << order);
}
-#endif
+
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
PAGE_SIZE << order);
return 0;
@@ -601,12 +551,9 @@ static __always_inline int charge_slab_p
static __always_inline void uncharge_slab_page(struct page *page, int order,
struct kmem_cache *s)
{
-#ifdef CONFIG_MEMCG_KMEM
- if (memcg_kmem_enabled() && !is_root_cache(s)) {
+ if (memcg_kmem_enabled() && !is_root_cache(s))
memcg_free_page_obj_cgroups(page);
- percpu_ref_put_many(&s->memcg_params.refcnt, 1 << order);
- }
-#endif
+
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
-(PAGE_SIZE << order));
}
@@ -749,9 +696,6 @@ static inline struct kmem_cache_node *ge
void *slab_start(struct seq_file *m, loff_t *pos);
void *slab_next(struct seq_file *m, void *p, loff_t *pos);
void slab_stop(struct seq_file *m, void *p);
-void *memcg_slab_start(struct seq_file *m, loff_t *pos);
-void *memcg_slab_next(struct seq_file *m, void *p, loff_t *pos);
-void memcg_slab_stop(struct seq_file *m, void *p);
int memcg_slab_show(struct seq_file *m, void *p);

#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)
--- a/mm/slub.c~mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-accounted-allocations
+++ a/mm/slub.c
@@ -4204,36 +4204,6 @@ int __kmem_cache_shrink(struct kmem_cach
return ret;
}

-#ifdef CONFIG_MEMCG
-void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
-{
- /*
- * Called with all the locks held after a sched RCU grace period.
- * Even if @s becomes empty after shrinking, we can't know that @s
- * doesn't have allocations already in-flight and thus can't
- * destroy @s until the associated memcg is released.
- *
- * However, let's remove the sysfs files for empty caches here.
- * Each cache has a lot of interface files which aren't
- * particularly useful for empty draining caches; otherwise, we can
- * easily end up with millions of unnecessary sysfs files on
- * systems which have a lot of memory and transient cgroups.
- */
- if (!__kmem_cache_shrink(s))
- sysfs_slab_remove(s);
-}
-
-void __kmemcg_cache_deactivate(struct kmem_cache *s)
-{
- /*
- * Disable empty slabs caching. Used to avoid pinning offline
- * memory cgroups by kmem pages that can be freed.
- */
- slub_set_cpu_partial(s, 0);
- s->min_partial = 0;
-}
-#endif /* CONFIG_MEMCG */
-
static int slab_mem_going_offline_callback(void *arg)
{
struct kmem_cache *s;
@@ -4390,7 +4360,7 @@ static struct kmem_cache * __init bootst
}
slab_init_memcg_params(s);
list_add(&s->list, &slab_caches);
- memcg_link_cache(s, NULL);
+ memcg_link_cache(s);
return s;
}

@@ -4458,7 +4428,8 @@ __kmem_cache_alias(const char *name, uns
s->object_size = max(s->object_size, size);
s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));

- for_each_memcg_cache(c, s) {
+ c = memcg_cache(s);
+ if (c) {
c->object_size = s->object_size;
c->inuse = max(c->inuse, ALIGN(size, sizeof(void *)));
}
@@ -5591,7 +5562,8 @@ static ssize_t slab_attr_store(struct ko
* directly either failed or succeeded, in which case we loop
* through the descendants with best-effort propagation.
*/
- for_each_memcg_cache(c, s)
+ c = memcg_cache(s);
+ if (c)
attribute->store(c, buf, len);
mutex_unlock(&slab_mutex);
}
_