[Devel] [PATCH -mm 2/6] memcg: allocate memcg_caches array on first per memcg cache creation
Vladimir Davydov
vdavydov at parallels.com
Fri Apr 25 05:33:08 PDT 2014
There is no need to allocate the memcg_caches array on kmem cache
creation, because we perfectly handle root caches without memcg_params
everywhere. Since not all caches will necessarily be used by memory
cgroups, this rather looks like a waste of memory. So let's allocate
the memcg_caches array on the first per memcg cache creation.
A couple of things to note about this patch:
- after it is applied memcg_{alloc, free}_cache_params do nothing for
root caches so that they can be inlined into memcg_kmem_{create,
destroy}_cache;
- since memcg_limited_groups_array_size is now accessed under
activate_kmem_mutex, we can move memcg_limited_groups_array_size
update (memcg_update_array_size) out of slab_mutex, which is nice,
because it isn't something specific to kmem caches - it will be used
in per memcg list_lru in the future;
- memcg_caches allocation scheme is now spread between slab_common.c
and memcontrol.c, but that'll be fixed by the next patches where I'll
move it completely to slab_common.c
Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
include/linux/slab.h | 1 +
mm/memcontrol.c | 64 +++++++++++++++++++++++++++++++-------------------
mm/slab_common.c | 41 ++++++++++++++++++++++++++++++++
3 files changed, 82 insertions(+), 24 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 86e5b26fbdab..095ce8e47a36 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -119,6 +119,7 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
struct kmem_cache *,
const char *);
+int kmem_cache_init_memcg_array(struct kmem_cache *, int);
#endif
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 605d72044533..fa7cbce8f0cf 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3059,6 +3059,9 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
VM_BUG_ON(!is_root_cache(s));
+ if (!cur_params)
+ return 0;
+
if (num_groups > memcg_limited_groups_array_size) {
int i;
struct memcg_cache_params *new_params;
@@ -3099,8 +3102,7 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
* anyway.
*/
rcu_assign_pointer(s->memcg_params, new_params);
- if (cur_params)
- kfree_rcu(cur_params, rcu_head);
+ kfree_rcu(cur_params, rcu_head);
}
return 0;
}
@@ -3108,40 +3110,52 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
struct kmem_cache *root_cache)
{
- size_t size;
-
- if (!memcg_kmem_enabled())
+ if (!memcg)
return 0;
- if (!memcg) {
- size = offsetof(struct memcg_cache_params, memcg_caches);
- size += memcg_limited_groups_array_size * sizeof(void *);
- } else
- size = sizeof(struct memcg_cache_params);
-
- s->memcg_params = kzalloc(size, GFP_KERNEL);
+ s->memcg_params = kzalloc(sizeof(*s->memcg_params), GFP_KERNEL);
if (!s->memcg_params)
return -ENOMEM;
- if (memcg) {
- s->memcg_params->memcg = memcg;
- s->memcg_params->root_cache = root_cache;
- css_get(&memcg->css);
- } else
- s->memcg_params->is_root_cache = true;
+ s->memcg_params->memcg = memcg;
+ s->memcg_params->root_cache = root_cache;
+ css_get(&memcg->css);
return 0;
}
void memcg_free_cache_params(struct kmem_cache *s)
{
- if (!s->memcg_params)
+ if (is_root_cache(s))
return;
- if (!s->memcg_params->is_root_cache)
- css_put(&s->memcg_params->memcg->css);
+ css_put(&s->memcg_params->memcg->css);
kfree(s->memcg_params);
}
+/*
+ * Prepares the memcg_caches array of the given kmem cache for disposing
+ * memcgs' copies.
+ */
+static int memcg_prepare_kmem_cache(struct kmem_cache *cachep)
+{
+ int ret;
+
+ BUG_ON(!is_root_cache(cachep));
+
+ if (cachep->memcg_params)
+ return 0;
+
+ /* activate_kmem_mutex guarantees a stable value of
+ * memcg_limited_groups_array_size */
+ mutex_lock(&activate_kmem_mutex);
+ mutex_lock(&memcg_slab_mutex);
+ ret = kmem_cache_init_memcg_array(cachep,
+ memcg_limited_groups_array_size);
+ mutex_unlock(&memcg_slab_mutex);
+ mutex_unlock(&activate_kmem_mutex);
+ return ret;
+}
+
static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
struct kmem_cache *root_cache)
{
@@ -3287,10 +3301,13 @@ static void memcg_create_cache_work_func(struct work_struct *w)
struct mem_cgroup *memcg = cw->memcg;
struct kmem_cache *cachep = cw->cachep;
+ if (memcg_prepare_kmem_cache(cachep) != 0)
+ goto out;
+
mutex_lock(&memcg_slab_mutex);
memcg_kmem_create_cache(memcg, cachep);
mutex_unlock(&memcg_slab_mutex);
-
+out:
css_put(&memcg->css);
kfree(cw);
}
@@ -3371,8 +3388,7 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
struct mem_cgroup *memcg;
struct kmem_cache *memcg_cachep;
- VM_BUG_ON(!cachep->memcg_params);
- VM_BUG_ON(!cachep->memcg_params->is_root_cache);
+ VM_BUG_ON(!is_root_cache(cachep));
if (!current->mm || current->memcg_kmem_skip_account)
return cachep;
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 6b6397d2e05e..44bfc4b1ee09 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -77,6 +77,45 @@ static inline int kmem_cache_sanity_check(const char *name, size_t size)
#endif
#ifdef CONFIG_MEMCG_KMEM
+static int kmem_cache_alloc_memcg_array(struct kmem_cache *s, int nr_entries)
+{
+ size_t size;
+ struct memcg_cache_params *new;
+
+ size = offsetof(struct memcg_cache_params, memcg_caches);
+ size += nr_entries * sizeof(void *);
+
+ new = kzalloc(size, GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
+
+ new->is_root_cache = true;
+
+ /* matching rcu_dereference is in cache_from_memcg_idx */
+ rcu_assign_pointer(s->memcg_params, new);
+
+ return 0;
+}
+
+static void kmem_cache_free_memcg_array(struct kmem_cache *s)
+{
+ kfree(s->memcg_params);
+ s->memcg_params = NULL;
+}
+
+int kmem_cache_init_memcg_array(struct kmem_cache *s, int nr_entries)
+{
+ int ret = 0;
+
+ BUG_ON(!is_root_cache(s));
+
+ mutex_lock(&slab_mutex);
+ if (!s->memcg_params)
+ ret = kmem_cache_alloc_memcg_array(s, nr_entries);
+ mutex_unlock(&slab_mutex);
+ return ret;
+}
+
int memcg_update_all_caches(int num_memcgs)
{
struct kmem_cache *s;
@@ -317,6 +356,8 @@ static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
rc = __kmem_cache_destroy_memcg_children(s);
mutex_lock(&slab_mutex);
+ if (rc == 0)
+ kmem_cache_free_memcg_array(s);
return rc;
}
#else
--
1.7.10.4
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