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authorVladimir Davydov <vdavydov@parallels.com>2014-04-07 15:39:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-07 16:36:12 -0700
commita44cb9449182fd7b25bf5f1cc38b7f19e0b96f6d (patch)
tree2edcdb2aed0a5c54f5397c943abc0a2bd41031b3 /mm/slab_common.c
parentcf7bc58f6dd4fdbab22e2ec5f27fe59674f425bf (diff)
downloadlinux-a44cb9449182fd7b25bf5f1cc38b7f19e0b96f6d.tar.bz2
memcg, slab: never try to merge memcg caches
When a kmem cache is created (kmem_cache_create_memcg()), we first try to find a compatible cache that already exists and can handle requests from the new cache, i.e. has the same object size, alignment, ctor, etc. If there is such a cache, we do not create any new caches, instead we simply increment the refcount of the cache found and return it. Currently we do this procedure not only when creating root caches, but also for memcg caches. However, there is no point in that, because, as every memcg cache has exactly the same parameters as its parent and cache merging cannot be turned off in runtime (only on boot by passing "slub_nomerge"), the root caches of any two potentially mergeable memcg caches should be merged already, i.e. it must be the same root cache, and therefore we couldn't even get to the memcg cache creation, because it already exists. The only exception is boot caches - they are explicitly forbidden to be merged by setting their refcount to -1. There are currently only two of them - kmem_cache and kmem_cache_node, which are used in slab internals (I do not count kmalloc caches as their refcount is set to 1 immediately after creation). Since they are prevented from merging preliminary I guess we should avoid to merge their children too. So let's remove the useless code responsible for merging memcg caches. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Rientjes <rientjes@google.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Glauber Costa <glommer@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab_common.c')
-rw-r--r--mm/slab_common.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 1ec3c619ba04..e77b51eb7347 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -200,9 +200,11 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
*/
flags &= CACHE_CREATE_MASK;
- s = __kmem_cache_alias(memcg, name, size, align, flags, ctor);
- if (s)
- goto out_unlock;
+ if (!memcg) {
+ s = __kmem_cache_alias(name, size, align, flags, ctor);
+ if (s)
+ goto out_unlock;
+ }
err = -ENOMEM;
s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);