Commit 63677c74 authored by Roman Gushchin's avatar Roman Gushchin Committed by Linus Torvalds

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 fa06235b ("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.comSigned-off-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 397162ff
......@@ -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);
......
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