[PATCH 14/16] mm: memcg/slab: use one set of kmem_caches for all memory cgroups

From: Roman Gushchin
Date: Thu Oct 17 2019 - 20:29:05 EST

This is fairly big but mostly red patch, which makes all non-root
slab allocations using 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.

Signed-off-by: Roman Gushchin <guro@xxxxxx>
---
include/linux/memcontrol.h | 5 +-
include/linux/slab.h | 3 +-
mm/memcontrol.c | 123 ++---------
mm/slab.c | 16 +-
mm/slab.h | 121 ++++-------
mm/slab_common.c | 414 ++++---------------------------------
mm/slub.c | 38 +---
7 files changed, 106 insertions(+), 614 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a75980559a47..f36203cf75f8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -327,7 +327,6 @@ 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 mem_cgroup_ptr __rcu *kmem_memcg_ptr;
struct list_head kmem_memcg_ptr_list;
#endif
@@ -1436,9 +1435,7 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
}
#endif

-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
- struct mem_cgroup **memcgp);
-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 page *page, gfp_t gfp, int order);
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 877a95c6a2d2..246474e9c706 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -155,8 +155,7 @@ struct kmem_cache *kmem_cache_create_usercopy(const char *name,
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 *);

/*
* Please use this macro to create slab caches. Simply specify the
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0c9698f03cfe..b0d0c833150c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -330,7 +330,7 @@ static void memcg_reparent_kmem_memcg_ptr(struct mem_cgroup *memcg,
}

/*
- * 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
@@ -2938,9 +2938,7 @@ 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;

@@ -2959,7 +2957,6 @@ 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;
};
@@ -2968,31 +2965,24 @@ static void memcg_kmem_cache_create_func(struct work_struct *w)
{
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)
return;

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

@@ -3000,96 +2990,26 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
}

/**
- * 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 mem_cgroup **memcgp)
+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)) {
- css_get(&memcg->css);
- *memcgp = memcg;
- 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;
}

/**
@@ -3669,7 +3589,6 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
*/
memcg->kmemcg_id = memcg_id;
memcg->kmem_state = KMEM_ONLINE;
- INIT_LIST_HEAD(&memcg->kmem_caches);

return 0;
}
@@ -3682,12 +3601,7 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)

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);
@@ -3695,12 +3609,10 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
parent = root_mem_cgroup;

/*
- * Deactivate and reparent kmem_caches and reparent kmem_memcg_ptr.
- * Then flush percpu slab statistics to have precise values at the
- * parent and all ancestor levels. It's required to keep slab stats
- * accurate after the reparenting of kmem_caches.
+ * Reparent kmem_memcg_ptr. Then flush percpu slab statistics to have
+ * precise values at the parent and all ancestor levels. It's required
+ * to keep slab stats accurate after the reparenting of kmem_caches.
*/
- memcg_deactivate_kmem_caches(memcg, parent);
memcg_reparent_kmem_memcg_ptr(memcg, parent);
memcg_flush_percpu_vmstats(memcg, true);

@@ -3736,10 +3648,8 @@ static void memcg_free_kmem(struct mem_cgroup *memcg)
if (unlikely(memcg->kmem_state == KMEM_ONLINE))
memcg_offline_kmem(memcg);

- if (memcg->kmem_state == KMEM_ALLOCATED) {
- WARN_ON(!list_empty(&memcg->kmem_caches));
+ if (memcg->kmem_state == KMEM_ALLOCATED)
static_branch_dec(&memcg_kmem_enabled_key);
- }
}
#else
static int memcg_online_kmem(struct mem_cgroup *memcg)
@@ -5316,9 +5226,6 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)

/* 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;
}
diff --git a/mm/slab.c b/mm/slab.c
index 91cd8bc4ee07..0914d7cd869f 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1239,7 +1239,7 @@ 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;

/*
@@ -2244,17 +2244,6 @@ int __kmem_cache_shrink(struct kmem_cache *cachep)
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);
@@ -3862,7 +3851,8 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
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);
}
diff --git a/mm/slab.h b/mm/slab.h
index a6330065d434..035c2969a2ca 100644
--- a/mm/slab.h
+++ b/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 */

@@ -234,8 +193,6 @@ bool __kmem_cache_empty(struct kmem_cache *);
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);

@@ -281,14 +238,6 @@ static inline int cache_vmstat_idx(struct kmem_cache *s)
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;
@@ -319,6 +268,13 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
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;
+}
+
/*
* 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,
@@ -367,17 +323,27 @@ static inline struct kmem_cache *memcg_slab_pre_alloc_hook(struct kmem_cache *s,
size_t size, gfp_t flags)
{
struct kmem_cache *cachep;
+ struct mem_cgroup *memcg;
+
+ if (memcg_kmem_bypass())
+ return s;

- cachep = memcg_kmem_get_cache(s, memcgp);
- if (is_root_cache(cachep))
+ memcg = get_mem_cgroup_from_current();
+ if (!memcg || mem_cgroup_is_root(memcg))
return s;

- if (__memcg_kmem_charge_subpage(*memcgp, size * s->size, flags)) {
- mem_cgroup_put(*memcgp);
- memcg_kmem_put_cache(cachep);
- cachep = NULL;
+ cachep = memcg_kmem_get_cache(s);
+ if (is_root_cache(cachep)) {
+ mem_cgroup_put(memcg);
+ return s;
}

+ if (__memcg_kmem_charge_subpage(memcg, size * s->size, flags)) {
+ mem_cgroup_put(memcg);
+ return NULL;
+ }
+
+ *memcgp = memcg;
return cachep;
}

@@ -407,8 +373,6 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
}
mem_cgroup_ptr_put(memcg_ptr);
mem_cgroup_put(memcg);
-
- memcg_kmem_put_cache(s);
}

static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
@@ -437,7 +401,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
}

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 */

@@ -445,9 +409,6 @@ extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
#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;
@@ -469,6 +430,11 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
return s;
}

+static inline struct kmem_cache *memcg_cache(struct kmem_cache *s)
+{
+ return NULL;
+}
+
static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr)
{
return NULL;
@@ -506,8 +472,7 @@ static inline void slab_init_memcg_params(struct kmem_cache *s)
{
}

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

@@ -535,8 +500,6 @@ static __always_inline int charge_slab_page(struct page *page,
ret = memcg_alloc_page_memcg_vec(page, gfp, objects);
if (ret)
return ret;
-
- percpu_ref_get_many(&s->memcg_params.refcnt, 1 << order);
}
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
PAGE_SIZE << order);
@@ -546,10 +509,9 @@ static __always_inline int charge_slab_page(struct page *page,
static __always_inline void uncharge_slab_page(struct page *page, int order,
struct kmem_cache *s)
{
- if (!is_root_cache(s)) {
+ if (!is_root_cache(s))
memcg_free_page_memcg_vec(page);
- percpu_ref_put_many(&s->memcg_params.refcnt, 1 << order);
- }
+
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
-(PAGE_SIZE << order));
}
@@ -698,9 +660,6 @@ static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
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)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index cc0c70b57c1c..3dcd90ba7525 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -131,141 +131,36 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
#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;
+ s->memcg_params.memcg_cache = NULL;
}

-static int init_memcg_params(struct kmem_cache *s,
- struct kmem_cache *root_cache)
+static void 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;
-
+ if (root_cache)
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);
- }
+ else
+ slab_init_memcg_params(s);
}

-static void free_memcg_params(struct rcu_head *rcu)
+void memcg_link_cache(struct kmem_cache *s)
{
- 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;
-}
-
-void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg)
-{
- 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)
{
}

@@ -380,7 +275,7 @@ static struct kmem_cache *create_cache(const char *name,
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;
@@ -400,24 +295,20 @@ static struct kmem_cache *create_cache(const char *name,
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;
}
@@ -504,7 +395,7 @@ kmem_cache_create_usercopy(const char *name,

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);
@@ -629,51 +520,27 @@ static int shutdown_cache(struct kmem_cache *s)

#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)
- 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])
+ if (root_cache->memcg_params.memcg_cache)
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;

@@ -681,7 +548,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
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
@@ -698,7 +565,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
* initialized.
*/
smp_wmb();
- arr->entries[idx] = s;
+ root_cache->memcg_params.memcg_cache = s;

out_unlock:
mutex_unlock(&slab_mutex);
@@ -707,197 +574,18 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
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 eariler.
- */
- 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 flush_memcg_workqueue(struct kmem_cache *s)
{
- spin_lock_irq(&memcg_kmem_wq_lock);
- s->memcg_params.dying = true;
- spin_unlock_irq(&memcg_kmem_wq_lock);
-
- /*
- * 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
@@ -919,7 +607,6 @@ static inline void flush_memcg_workqueue(struct kmem_cache *s)
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);
}
@@ -983,7 +670,7 @@ int kmem_cache_shrink(struct kmem_cache *cachep)
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)
@@ -1000,21 +687,11 @@ void kmem_cache_shrink_all(struct kmem_cache *s)
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();
}
@@ -1069,7 +746,7 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name,

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;
}
@@ -1431,7 +1108,8 @@ memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
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);

@@ -1562,7 +1240,7 @@ 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)
{
@@ -1574,9 +1252,9 @@ static int memcg_slabinfo_show(struct seq_file *m, void *unused)
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));
@@ -1585,23 +1263,13 @@ static int memcg_slabinfo_show(struct seq_file *m, void *unused)
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;
diff --git a/mm/slub.c b/mm/slub.c
index a62545c7acac..53abbf0831b6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4057,36 +4057,6 @@ int __kmem_cache_shrink(struct kmem_cache *s)
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;
@@ -4243,7 +4213,7 @@ static struct kmem_cache * __init bootstrap(struct kmem_cache *static_cache)
}
slab_init_memcg_params(s);
list_add(&s->list, &slab_caches);
- memcg_link_cache(s, NULL);
+ memcg_link_cache(s);
return s;
}

@@ -4311,7 +4281,8 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
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 *)));
}
@@ -5582,7 +5553,8 @@ static ssize_t slab_attr_store(struct kobject *kobj,
* 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);
}
--
2.21.0