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authorGlauber Costa <glommer@parallels.com>2012-12-18 14:22:11 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-18 15:02:13 -0800
commitbea207c86e4eb158bf20f7b36bee72da9272e8d3 (patch)
tree9e100534378fa916f739b6a595508b40eabc35c0
parenta8964b9b84f99c0b1b5d7c09520f89f0700e742e (diff)
memcg: allow a memcg with kmem charges to be destructed
Because the ultimate goal of the kmem tracking in memcg is to track slab pages as well, we can't guarantee that we'll always be able to point a page to a particular process, and migrate the charges along with it - since in the common case, a page will contain data belonging to multiple processes. Because of that, when we destroy a memcg, we only make sure the destruction will succeed by discounting the kmem charges from the user charges when we try to empty the cgroup. Signed-off-by: Glauber Costa <glommer@parallels.com> Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Frederic Weisbecker <fweisbec@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: JoonSoo Kim <js1304@gmail.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Rik van Riel <riel@redhat.com> Cc: Suleiman Souhlal <suleiman@google.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/memcontrol.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bc70254558fa..f96ccc90fa66 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -547,6 +547,11 @@ static void disarm_kmem_keys(struct mem_cgroup *memcg)
{
if (memcg_kmem_is_active(memcg))
static_key_slow_dec(&memcg_kmem_enabled_key);
+ /*
+ * This check can't live in kmem destruction function,
+ * since the charges will outlive the cgroup
+ */
+ WARN_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);
}
#else
static void disarm_kmem_keys(struct mem_cgroup *memcg)
@@ -4025,6 +4030,7 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
{
int node, zid;
+ u64 usage;
do {
/* This is for making all *used* pages to be on LRU. */
@@ -4045,13 +4051,20 @@ static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
cond_resched();
/*
+ * Kernel memory may not necessarily be trackable to a specific
+ * process. So they are not migrated, and therefore we can't
+ * expect their value to drop to 0 here.
+ * Having res filled up with kmem only is enough.
+ *
* This is a safety check because mem_cgroup_force_empty_list
* could have raced with mem_cgroup_replace_page_cache callers
* so the lru seemed empty but the page could have been added
* right after the check. RES_USAGE should be safe as we always
* charge before adding to the LRU.
*/
- } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0);
+ usage = res_counter_read_u64(&memcg->res, RES_USAGE) -
+ res_counter_read_u64(&memcg->kmem, RES_USAGE);
+ } while (usage > 0);
}
/*