A removed memory cgroup with a defined low limit 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. Fix this issue by zeroing memcg->low during memcg offlining. Signed-off-by: Roman Gushchin <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Vladimir Davydov <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] --- mm/memcontrol.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index aed11b2d0251..2aa204b8f9fd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4300,6 +4300,8 @@ 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); -- 2.13.3
