[PATCH -mm 06/12] memcg: keep all children of each root cache on a list

From: Vladimir Davydov
Date: Wed Feb 26 2014 - 10:11:46 EST

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Sometimes we need to iterate over all child caches of a particular root
cache, e.g. when we are destroying it. Currently each root cache keeps
pointers to its children in its memcg_cache_params::memcg_caches_array
so that we can enumerate all active kmemcg ids dereferencing appropriate
array slots to get a memcg. However, this is going to change when memcg
cache reparenting is introduced - only active (not dead) caches will
reside in this array. So let's organize all child caches of the same
root cache into a list on memcg_cache_params.

Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxx>
---
include/linux/memcontrol.h | 2 +-
include/linux/slab.h | 3 +++
mm/memcontrol.c | 36 +++++++++++++++++++-----------------
mm/slab.c | 38 ++++++++++++++++++++++----------------
mm/slab_common.c | 19 +++++++++----------
mm/slub.c | 41 +++++++++++++++++++++++++----------------
6 files changed, 79 insertions(+), 60 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6128323ea453..b38b52ce59fb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -512,7 +512,7 @@ void memcg_update_array_size(int num_groups);
struct kmem_cache *
__memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);

-int kmem_cache_destroy_memcg_children(struct kmem_cache *s);
+void kmem_cache_destroy_memcg_children(struct kmem_cache *s);

/**
* memcg_kmem_newpage_charge: verify if a new kmem allocation is allowed.
diff --git a/include/linux/slab.h b/include/linux/slab.h
index f2fd4212976e..8091d009cd72 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -524,6 +524,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
* @memcg: pointer to the memcg this cache belongs to
* @list: list_head for the list of all caches in this memcg
* @root_cache: pointer to the global, root cache, this cache was derived from
+ * @siblings: list_head for the list of all child caches of the root_cache
* @refcount: the reference counter; cache destruction will be scheduled when
* it reaches zero
* @destroy: worker to be called whenever we are ready, or believe we may be
@@ -533,6 +534,7 @@ struct memcg_cache_params {
bool is_root_cache;
union {
struct {
+ struct list_head children;
struct rcu_head rcu_head;
struct kmem_cache *memcg_caches[0];
};
@@ -541,6 +543,7 @@ struct memcg_cache_params {
struct mem_cgroup *memcg;
struct list_head list;
struct kmem_cache *root_cache;
+ struct list_head siblings;
atomic_t refcount;
struct work_struct destroy;
};
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5eb629ed28d6..6af3c062dfb1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3114,6 +3114,10 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
return -ENOMEM;

new_params->is_root_cache = true;
+ INIT_LIST_HEAD(&new_params->children);
+ if (cur_params)
+ list_splice(&cur_params->children,
+ &new_params->children);

/*
* There is the chance it will be bigger than
@@ -3196,8 +3200,10 @@ int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
kmem_cache_destroy_work_func);
atomic_set(&s->memcg_params->refcount, 1);
css_get(&memcg->css);
- } else
+ } else {
s->memcg_params->is_root_cache = true;
+ INIT_LIST_HEAD(&s->memcg_params->children);
+ }

return 0;
}
@@ -3237,6 +3243,8 @@ void memcg_register_cache(struct kmem_cache *s)
*/
smp_wmb();

+ list_add(&s->memcg_params->siblings, &root->memcg_params->children);
+
VM_BUG_ON(root->memcg_params->memcg_caches[id]);
root->memcg_params->memcg_caches[id] = s;

@@ -3264,6 +3272,8 @@ void memcg_unregister_cache(struct kmem_cache *s)
memcg = s->memcg_params->memcg;
id = memcg_cache_id(memcg);

+ list_del(&s->memcg_params->siblings);
+
mutex_lock(&memcg->slab_caches_mutex);
list_del(&s->memcg_params->list);
mutex_unlock(&memcg->slab_caches_mutex);
@@ -3326,10 +3336,9 @@ static void kmem_cache_destroy_work_func(struct work_struct *w)
kmem_cache_destroy_memcg(cachep, false);
}

-int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
{
- struct kmem_cache *c;
- int i, failed = 0;
+ struct memcg_cache_params *params, *tmp;

/*
* Since the cache is being destroyed, it shouldn't be allocated from
@@ -3341,9 +3350,9 @@ int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
flush_workqueue(memcg_cache_create_wq);

/*
- * If the cache is being destroyed, we trust that there is no one else
- * requesting objects from it. Even if there are, the sanity checks in
- * kmem_cache_destroy should caught this ill-case.
+ * At this point nobody except us is allowed to create or destroy child
+ * caches so we don't need to take the slab_mutex for iterating over
+ * the children list.
*
* Still, we don't want anyone else freeing memcg_caches under our
* noses, which can happen if a new memcg comes to life. As usual,
@@ -3351,17 +3360,10 @@ int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
* this.
*/
mutex_lock(&activate_kmem_mutex);
- for_each_memcg_cache_index(i) {
- c = cache_from_memcg_idx(s, i);
- if (!c)
- continue;
-
- kmem_cache_destroy_memcg(c, true);
- if (cache_from_memcg_idx(s, i))
- failed++;
- }
+ list_for_each_entry_safe(params, tmp,
+ &s->memcg_params->children, siblings)
+ kmem_cache_destroy_memcg(params->cachep, true);
mutex_unlock(&activate_kmem_mutex);
- return failed;
}

static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
diff --git a/mm/slab.c b/mm/slab.c
index 9b8950cb64dd..eae95847cdef 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3816,29 +3816,35 @@ static int __do_tune_cpucache(struct kmem_cache *cachep, int limit,
return alloc_kmemlist(cachep, gfp);
}

+static void __do_tune_cpucache_memcg(struct kmem_cache *cachep, int limit,
+ int batchcount, int shared, gfp_t gfp)
+{
+#ifdef CONFIG_MEMCG_KMEM
+ struct memcg_cache_params *params;
+
+ if (!cachep->memcg_params ||
+ !cachep->memcg_params->is_root_cache)
+ return;
+
+ lockdep_assert_held(&slab_mutex);
+ list_for_each_entry(params,
+ &cachep->memcg_params->children, siblings)
+ __do_tune_cpucache(params->cachep, limit,
+ batchcount, shared, gfp);
+#endif
+}
+
static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
int batchcount, int shared, gfp_t gfp)
{
int ret;
- struct kmem_cache *c = NULL;
- int i = 0;

ret = __do_tune_cpucache(cachep, limit, batchcount, shared, gfp);
-
- if (slab_state < FULL)
- return ret;
-
- if ((ret < 0) || !is_root_cache(cachep))
- return ret;
-
- VM_BUG_ON(!mutex_is_locked(&slab_mutex));
- for_each_memcg_cache_index(i) {
- c = cache_from_memcg_idx(cachep, i);
- if (c)
- /* return value determined by the parent cache only */
- __do_tune_cpucache(c, limit, batchcount, shared, gfp);
+ if (!ret) {
+ /* return value determined by the parent cache only */
+ __do_tune_cpucache_memcg(cachep, limit,
+ batchcount, shared, gfp);
}
-
return ret;
}

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 05ba3cd1b507..48e472894511 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -335,7 +335,8 @@ static int __kmem_cache_shutdown_memcg(struct kmem_cache *s,

mutex_unlock(&slab_mutex);
if (s->memcg_params->is_root_cache) {
- rc = kmem_cache_destroy_memcg_children(s);
+ kmem_cache_destroy_memcg_children(s);
+ rc = !list_empty(&s->memcg_params->children);
} else {
/*
* There might be a destruction work pending, which needs to be
@@ -693,20 +694,17 @@ void slab_stop(struct seq_file *m, void *p)
static void
memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
{
- struct kmem_cache *c;
+#ifdef CONFIG_MEMCG_KMEM
+ struct memcg_cache_params *params;
struct slabinfo sinfo;
- int i;

- if (!is_root_cache(s))
+ if (!s->memcg_params ||
+ !s->memcg_params->is_root_cache)
return;

- for_each_memcg_cache_index(i) {
- c = cache_from_memcg_idx(s, i);
- if (!c)
- continue;
-
+ list_for_each_entry(params, &s->memcg_params->children, siblings) {
memset(&sinfo, 0, sizeof(sinfo));
- get_slabinfo(c, &sinfo);
+ get_slabinfo(params->cachep, &sinfo);

info->active_slabs += sinfo.active_slabs;
info->num_slabs += sinfo.num_slabs;
@@ -714,6 +712,7 @@ memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
info->active_objs += sinfo.active_objs;
info->num_objs += sinfo.num_objs;
}
+#endif
}

int cache_show(struct kmem_cache *s, struct seq_file *m)
diff --git a/mm/slub.c b/mm/slub.c
index 4a10126fec3a..52864a6cb681 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3740,6 +3740,25 @@ static struct kmem_cache *find_mergeable(size_t size, size_t align,
return NULL;
}

+static void memcg_slab_merge(struct kmem_cache *s, size_t size)
+{
+#ifdef CONFIG_MEMCG_KMEM
+ struct kmem_cache *cachep;
+ struct memcg_cache_params *params;
+
+ if (!s->memcg_params)
+ return;
+ BUG_ON(!s->memcg_params->is_root_cache);
+
+ list_for_each_entry(params, &s->memcg_params->children, siblings) {
+ cachep = params->cachep;
+ cachep->object_size = s->object_size;
+ cachep->inuse = max_t(int, cachep->inuse,
+ ALIGN(size, sizeof(void *)));
+ }
+#endif
+}
+
struct kmem_cache *
__kmem_cache_alias(const char *name, size_t size, size_t align,
unsigned long flags, void (*ctor)(void *))
@@ -3748,9 +3767,6 @@ __kmem_cache_alias(const char *name, size_t size, size_t align,

s = find_mergeable(size, align, flags, name, ctor);
if (s) {
- int i;
- struct kmem_cache *c;
-
s->refcount++;

/*
@@ -3760,14 +3776,7 @@ __kmem_cache_alias(const char *name, size_t size, size_t align,
s->object_size = max(s->object_size, (int)size);
s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));

- for_each_memcg_cache_index(i) {
- c = cache_from_memcg_idx(s, i);
- if (!c)
- continue;
- c->object_size = s->object_size;
- c->inuse = max_t(int, c->inuse,
- ALIGN(size, sizeof(void *)));
- }
+ memcg_slab_merge(s, size);

if (sysfs_slab_alias(s, name)) {
s->refcount--;
@@ -5027,7 +5036,7 @@ static ssize_t slab_attr_store(struct kobject *kobj,
err = attribute->store(s, buf, len);
#ifdef CONFIG_MEMCG_KMEM
if (slab_state >= FULL && err >= 0 && is_root_cache(s)) {
- int i;
+ struct memcg_cache_params *params;

mutex_lock(&slab_mutex);
if (s->max_attr_size < len)
@@ -5050,10 +5059,10 @@ 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_index(i) {
- struct kmem_cache *c = cache_from_memcg_idx(s, i);
- if (c)
- attribute->store(c, buf, len);
+ if (s->memcg_params) {
+ list_for_each_entry(params,
+ &s->memcg_params->children, siblings)
+ attribute->store(params->cachep, buf, len);
}
mutex_unlock(&slab_mutex);
}
--
1.7.10.4

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Next message: Vladimir Davydov: "[PATCH -mm 03/12] memcg: fix root vs memcg cache destruction race"
Previous message: Thierry Reding: "[GIT PULL] pwm: Fixes for v3.14-rc5"
In reply to: Vladimir Davydov: "[PATCH -mm 10/12] memcg: kill GFP_KMEMCG and stuff"
Next in thread: Vladimir Davydov: "[PATCH -mm 03/12] memcg: fix root vs memcg cache destruction race"
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