Commit 90cbc250 authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
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vmscan: force scan offline memory cgroups 



Since commit b2052564 ("mm: memcontrol: continue cache reclaim from
offlined groups") pages charged to a memory cgroup are not reparented when
the cgroup is removed.  Instead, they are supposed to be reclaimed in a
regular way, along with pages accounted to online memory cgroups.

However, an lruvec of an offline memory cgroup will sooner or later get so
small that it will be scanned only at low scan priorities (see
get_scan_count()).  Therefore, if there are enough reclaimable pages in
big lruvecs, pages accounted to offline memory cgroups will never be
scanned at all, wasting memory.

Fix this by unconditionally forcing scanning dead lruvecs from kswapd.

[akpm@linux-foundation.org: fix build]
Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
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 81422f29

include/linux/memcontrol.h

+6 −0
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ void mem_cgroup_iter_break(struct mem_cgroup *, struct mem_cgroup *); 
 * For memory reclaim.

 */

int mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec);

bool mem_cgroup_lruvec_online(struct lruvec *lruvec);

int mem_cgroup_select_victim_node(struct mem_cgroup *memcg);

unsigned long mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list);

void mem_cgroup_update_lru_size(struct lruvec *, enum lru_list, int);
@@ -266,6 +267,11 @@ mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec) 
	return 1;

}



static inline bool mem_cgroup_lruvec_online(struct lruvec *lruvec)

{

	return true;

}



static inline unsigned long

mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)

{

mm/memcontrol.c

+14 −0
Original line number Diff line number Diff line
@@ -1367,6 +1367,20 @@ int mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec) 
	return inactive * inactive_ratio < active;

}



bool mem_cgroup_lruvec_online(struct lruvec *lruvec)

{

	struct mem_cgroup_per_zone *mz;

	struct mem_cgroup *memcg;



	if (mem_cgroup_disabled())

		return true;



	mz = container_of(lruvec, struct mem_cgroup_per_zone, lruvec);

	memcg = mz->memcg;



	return !!(memcg->css.flags & CSS_ONLINE);

}



#define mem_cgroup_from_counter(counter, member)	\

	container_of(counter, struct mem_cgroup, member)

mm/vmscan.c

+6 −2
Original line number Diff line number Diff line
@@ -1903,8 +1903,12 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness, 
	 * latencies, so it's better to scan a minimum amount there as

	 * well.

	 */

	if (current_is_kswapd() && !zone_reclaimable(zone))

	if (current_is_kswapd()) {

		if (!zone_reclaimable(zone))

			force_scan = true;

		if (!mem_cgroup_lruvec_online(lruvec))

			force_scan = true;

	}

	if (!global_reclaim(sc))

		force_scan = true;

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