From 63677c745d63ba75ef97a7728c85168ddd6c0040 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Wed, 6 Sep 2017 16:21:47 -0700 Subject: [PATCH] mm, memcg: reset memory.low during memcg offlining A removed memory cgroup with a defined memory.low and some belonging pagecache has very low chances to be freed. If a cgroup has been removed, there is likely no memory pressure inside the cgroup, and the pagecache is protected from the external pressure by the defined low limit. The cgroup will be freed only after the reclaim of all belonging pages. And it will not happen until there are any reclaimable memory in the system. That means, there is a good chance, that a cold pagecache will reside in the memory for an undefined amount of time, wasting system resources. This problem was fixed earlier by fa06235b8eb0 ("cgroup: reset css on destruction"), but it's not a best way to do it, as we can't really reset all limits/counters during cgroup offlining. Link: http://lkml.kernel.org/r/20170727130428.28856-1-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Johannes Weiner Acked-by: Michal Hocko Cc: Vladimir Davydov Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e09741af816f..2926c44519b6 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4319,6 +4319,8 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) } spin_unlock(&memcg->event_list_lock); + memcg->low = 0; + memcg_offline_kmem(memcg); wb_memcg_offline(memcg); -- 2.20.1