From a2d7f8e461881394167bafb616112a96f5f567d0 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Wed, 3 May 2017 14:52:03 -0700 Subject: [PATCH] mm: don't avoid high-priority reclaim on unreclaimable nodes Commit 246e87a93934 ("memcg: fix get_scan_count() for small targets") sought to avoid high reclaim priorities for kswapd by forcing it to scan a minimum amount of pages when lru_pages >> priority yielded nothing. Commit b95a2f2d486d ("mm: vmscan: convert global reclaim to per-memcg LRU lists"), due to switching global reclaim to a round-robin scheme over all cgroups, had to restrict this forceful behavior to unreclaimable zones in order to prevent massive overreclaim with many cgroups. The latter patch effectively neutered the behavior completely for all but extreme memory pressure. But in those situations we might as well drop the reclaimers to lower priority levels. Remove the check. Link: http://lkml.kernel.org/r/20170228214007.5621-6-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Hillf Danton Acked-by: Michal Hocko Cc: Jia He Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 014d0d181be0..2fd50ca88016 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2130,22 +2130,13 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, int pass; /* - * If the zone or memcg is small, nr[l] can be 0. This - * results in no scanning on this priority and a potential - * priority drop. Global direct reclaim can go to the next - * zone and tends to have no problems. Global kswapd is for - * zone balancing and it needs to scan a minimum amount. When + * If the zone or memcg is small, nr[l] can be 0. When * reclaiming for a memcg, a priority drop can cause high - * latencies, so it's better to scan a minimum amount there as - * well. + * latencies, so it's better to scan a minimum amount. When a + * cgroup has already been deleted, scrape out the remaining + * cache forcefully to get rid of the lingering state. */ - if (current_is_kswapd()) { - if (!pgdat_reclaimable(pgdat)) - force_scan = true; - if (!mem_cgroup_online(memcg)) - force_scan = true; - } - if (!global_reclaim(sc)) + if (!global_reclaim(sc) || !mem_cgroup_online(memcg)) force_scan = true; /* If we have no swap space, do not bother scanning anon pages. */ -- 2.20.1