[PATCH -mm 04/14] memcg: use mem_cgroup_id for per memcg cache naming

Vladimir Davydov
2014-09-21T15:14:36Z

Currently, we use memcg_cache_id as a part of a per memcg cache name.
Since memcg_cache_id is released only on css free, this guarantees cache
name uniqueness.

However, it's a bad practice to keep memcg_cache_id till css free,
because it occupies a slot in kmem_cache->memcg_params->memcg_caches
arrays. So I'm going to make memcg release memcg_cache_id on css
offline. As a result, memcg_cache_id won't guarantee cache name
uniqueness any more.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
include/linux/slab.h | 2 +-
mm/memcontrol.c | 13 +++++++++++--
mm/slab_common.c | 15 +++------------
3 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index c265bec6a57d..f4d489aee6cb 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -118,7 +118,7 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
#ifdef CONFIG_MEMCG_KMEM
struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *,
struct kmem_cache *,
- const char *);
+ char *);
#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 7361bd8b720a..16fcdbef1b7d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2995,6 +2995,7 @@ static void memcg_register_cache(struct mem_cgroup *memcg,
static char memcg_name_buf[NAME_MAX + 1]; /* protected by
memcg_slab_mutex */
struct kmem_cache *cachep;
+ char *cache_name;
int id;

lockdep_assert_held(&memcg_slab_mutex);
@@ -3010,14 +3011,22 @@ static void memcg_register_cache(struct mem_cgroup *memcg,
return;

cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
- cachep = memcg_create_kmem_cache(memcg, root_cache, memcg_name_buf);
+
+ cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
+ mem_cgroup_id(memcg), memcg_name_buf);
+ if (!cache_name)
+ return;
+
+ cachep = memcg_create_kmem_cache(memcg, root_cache, cache_name);
/*
* 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
* cache.
*/
- if (!cachep)
+ if (!cachep) {
+ kfree(cache_name);
return;
+ }

css_get(&memcg->css);
list_add(&cachep->memcg_params->list, &memcg->memcg_slab_caches);
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 800314e2a075..8b486f05c414 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -345,7 +345,7 @@ EXPORT_SYMBOL(kmem_cache_create);
* memcg_create_kmem_cache - Create a cache for a memory cgroup.
* @memcg: The memory cgroup the new cache is for.
* @root_cache: The parent of the new cache.
- * @memcg_name: The name of the memory cgroup (used for naming the new cache).
+ * @cache_name: The string to be used as the new cache name.
*
* This function attempts to create a kmem cache that will serve allocation
* requests going from @memcg to @root_cache. The new cache inherits properties
@@ -353,31 +353,22 @@ EXPORT_SYMBOL(kmem_cache_create);
*/
struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
struct kmem_cache *root_cache,
- const char *memcg_name)
+ char *cache_name)
{
struct kmem_cache *s = NULL;
- char *cache_name;

get_online_cpus();
get_online_mems();

mutex_lock(&slab_mutex);

- cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
- memcg_cache_id(memcg), memcg_name);
- if (!cache_name)
- goto out_unlock;
-
s = do_kmem_cache_create(cache_name, root_cache->object_size,
root_cache->size, root_cache->align,
root_cache->flags, root_cache->ctor,
memcg, root_cache);
- if (IS_ERR(s)) {
- kfree(cache_name);
+ if (IS_ERR(s))
s = NULL;
- }

-out_unlock:
mutex_unlock(&slab_mutex);

put_online_mems();