[PATCH] mm: memcontrol: drain memcg stock on force_empty

[Shakeel Butt <shakeelb@google.com>]

From: Junaid Shahid <junaids@google.com>

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.

Signed-off-by: Junaid Shahid <juanids@google.com>
Signed-off-by: Shakeel Butt <shakeelb@google.com>
---
 mm/memcontrol.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e2d33a37f971..2c3c69524b49 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2841,6 +2841,9 @@ 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;
-- 
2.17.0.441.gb46fe60e1d-goog