memcg: fix direct softlimit reclaim to be called in limit path (ac34a1a3) · Commits · 戴 / test

Commit ("memcg: add the soft_limit reclaim in global direct reclaim") adds a softlimit hook to shrink_zones(). By this, soft limit is called as try_to_free_pages() do_try_to_free_pages() shrink_zones() mem_cgroup_soft_limit_reclaim() Then, direct reclaim is memcg softlimit hint aware, now. But, the memory cgroup's "limit" path can call softlimit shrinker. try_to_free_mem_cgroup_pages() do_try_to_free_pages() shrink_zones() mem_cgroup_soft_limit_reclaim() This will cause a global reclaim when a memcg hits limit. This is bug. soft_limit_reclaim() should be called when scanning_global_lru(sc) == true. And the commit adds a variable "total_scanned" for counting softlimit scanned pages....it's not "total". This patch removes the variable and update sc->nr_scanned instead of it. This will affect shrink_slab()'s scan condition but, global LRU is scanned by softlimit and I think this change makes sense. TODO: avoid too much scanning of a zone when softlimit did enough work. Signed-off-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Ying Han <yinghan@google.com> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

+15 −12

Original line number	Diff line number	Diff line
		@@ -1995,14 +1995,13 @@ restart:
		* If a zone is deemed to be full of pinned pages then just give it a light
		* scan then give up on it.
		*/
		static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
		static void shrink_zones(int priority, struct zonelist *zonelist,
		struct scan_control *sc)
		{
		struct zoneref *z;
		struct zone *zone;
		unsigned long nr_soft_reclaimed;
		unsigned long nr_soft_scanned;
		unsigned long total_scanned = 0;

		for_each_zone_zonelist_nodemask(zone, z, zonelist,
		gfp_zone(sc->gfp_mask), sc->nodemask) {
		@@ -2017,19 +2016,23 @@ static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
		continue;
		if (zone->all_unreclaimable && priority != DEF_PRIORITY)
		continue; /* Let kswapd poll it */
		}

		/*
		* This steals pages from memory cgroups over softlimit
		* and returns the number of reclaimed pages and
		* scanned pages. This works for global memory pressure
		* and balancing, not for a memcg's limit.
		*/
		nr_soft_scanned = 0;
		nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
		sc->order, sc->gfp_mask,
		&nr_soft_scanned);
		sc->nr_reclaimed += nr_soft_reclaimed;
		total_scanned += nr_soft_scanned;
		sc->nr_scanned += nr_soft_scanned;
		/* need some check for avoid more shrink_zone() */
		}

		shrink_zone(priority, zone, sc);
		}

		return total_scanned;
		}

		static bool zone_reclaimable(struct zone *zone)
		@@ -2094,7 +2097,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
		sc->nr_scanned = 0;
		if (!priority)
		disable_swap_token(sc->mem_cgroup);
		total_scanned += shrink_zones(priority, zonelist, sc);
		shrink_zones(priority, zonelist, sc);
		/*
		* Don't shrink slabs when reclaiming memory from
		* over limit cgroups

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