[PATCH] memcg: do not account memory used for cache creation

[Glauber Costa <glommer@openvz.org>]

The memory we used to hold the memcg arrays is currently accounted to
the current memcg. But that creates a problem, because that memory can
only be freed after the last user is gone. Our only way to know which is
the last user, is to hook up to freeing time, but the fact that we still
have some in flight kmallocs will prevent freeing to happen. I believe
therefore to be just easier to account this memory as global overhead.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

---
I noticed this while testing nuances of the shrinker patches. The
caches would basically stay present forever, even if we managed to
flush all of the actual memory being used. With this patch applied,
they would go away all right.
---
 mm/memcontrol.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5d8b93a..aa1cbd4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5642,7 +5642,9 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)
 	static_key_slow_inc(&memcg_kmem_enabled_key);
 
 	mutex_lock(&set_limit_mutex);
+	memcg_stop_kmem_account();
 	ret = memcg_update_cache_sizes(memcg);
+	memcg_resume_kmem_account();
 	mutex_unlock(&set_limit_mutex);
 out:
 	return ret;
-- 
1.8.1.4

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