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authorTejun Heo <tj@kernel.org>2017-02-22 15:41:21 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-22 16:41:27 -0800
commitbc2791f857e1984b7548d2a2de2ffb1a913dee62 (patch)
tree1cf8a24fe4da02037d1b37de3e49eb7dec708834 /include
parent9eeadc8b6e0e31f9aea1f8886ef472f62c2b7f55 (diff)
slab: link memcg kmem_caches on their associated memory cgroup
With kmem cgroup support enabled, kmem_caches can be created and destroyed frequently and a great number of near empty kmem_caches can accumulate if there are a lot of transient cgroups and the system is not under memory pressure. When memory reclaim starts under such conditions, it can lead to consecutive deactivation and destruction of many kmem_caches, easily hundreds of thousands on moderately large systems, exposing scalability issues in the current slab management code. This is one of the patches to address the issue. While a memcg kmem_cache is listed on its root cache's ->children list, there is no direct way to iterate all kmem_caches which are assocaited with a memory cgroup. The only way to iterate them is walking all caches while filtering out caches which don't match, which would be most of them. This makes memcg destruction operations O(N^2) where N is the total number of slab caches which can be huge. This combined with the synchronous RCU operations can tie up a CPU and affect the whole machine for many hours when memory reclaim triggers offlining and destruction of the stale memcgs. This patch adds mem_cgroup->kmem_caches list which goes through memcg_cache_params->kmem_caches_node of all kmem_caches which are associated with the memcg. All memcg specific iterations, including stat file access, are updated to use the new list instead. Link: http://lkml.kernel.org/r/20170117235411.9408-6-tj@kernel.org Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jay Vana <jsvana@fb.com> Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/memcontrol.h1
-rw-r--r--include/linux/slab.h3
2 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 254698856b8f..9fcece9be85d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -253,6 +253,7 @@ 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;
#endif
int last_scanned_node;
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 1f611ba00f1d..a0cc7a77cda2 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -565,6 +565,8 @@ struct memcg_cache_array {
* @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.
*/
struct memcg_cache_params {
struct kmem_cache *root_cache;
@@ -576,6 +578,7 @@ struct memcg_cache_params {
struct {
struct mem_cgroup *memcg;
struct list_head children_node;
+ struct list_head kmem_caches_node;
};
};
};

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