mm: memcontrol: drain memcg stock on force_empty

The per-cpu memcg stock can retain a charge of upto 32 pages.  On a
machine with large number of cpus, this can amount to a decent amount of
memory.  Additionally force_empty interface might be triggering unneeded
memcg reclaims.

Link: http://lkml.kernel.org/r/20180507201651.165879-1-shakeelb@google.com
Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 18dcdac0b158..e6de0d6a3a8d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2610,6 +2610,9 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
 
         /* we call try-to-free pages for make this cgroup empty */
         lru_add_drain_all();
+
+        drain_all_stock(memcg);
+
         /* try to free all pages in this cgroup */
         while (nr_retries && page_counter_read(&memcg->memory)) {
                 int progress;