From 2ab051e11bfa3cbb7b24177f3d6aaed10a0d743e Mon Sep 17 00:00:00 2001 From: Jerome Marchand Date: Wed, 6 Aug 2014 16:08:03 -0700 Subject: [PATCH] memcg, vmscan: Fix forced scan of anonymous pages When memory cgoups are enabled, the code that decides to force to scan anonymous pages in get_scan_count() compares global values (free, high_watermark) to a value that is restricted to a memory cgroup (file). It make the code over-eager to force anon scan. For instance, it will force anon scan when scanning a memcg that is mainly populated by anonymous page, even when there is plenty of file pages to get rid of in others memcgs, even when swappiness == 0. It breaks user's expectation about swappiness and hurts performance. This patch makes sure that forced anon scan only happens when there not enough file pages for the all zone, not just in one random memcg. [hannes@cmpxchg.org: cleanups] Signed-off-by: Jerome Marchand Acked-by: Michal Hocko Acked-by: Johannes Weiner Reviewed-by: Rik van Riel Cc: Mel Gorman Signed-off-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 88ab53c9949a..d2f65c856350 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1930,11 +1930,6 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness, goto out; } - anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) + - get_lru_size(lruvec, LRU_INACTIVE_ANON); - file = get_lru_size(lruvec, LRU_ACTIVE_FILE) + - get_lru_size(lruvec, LRU_INACTIVE_FILE); - /* * Prevent the reclaimer from falling into the cache trap: as * cache pages start out inactive, every cache fault will tip @@ -1945,9 +1940,14 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness, * anon pages. Try to detect this based on file LRU size. */ if (global_reclaim(sc)) { - unsigned long free = zone_page_state(zone, NR_FREE_PAGES); + unsigned long zonefile; + unsigned long zonefree; + + zonefree = zone_page_state(zone, NR_FREE_PAGES); + zonefile = zone_page_state(zone, NR_ACTIVE_FILE) + + zone_page_state(zone, NR_INACTIVE_FILE); - if (unlikely(file + free <= high_wmark_pages(zone))) { + if (unlikely(zonefile + zonefree <= high_wmark_pages(zone))) { scan_balance = SCAN_ANON; goto out; } @@ -1982,6 +1982,12 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness, * * anon in [0], file in [1] */ + + anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) + + get_lru_size(lruvec, LRU_INACTIVE_ANON); + file = get_lru_size(lruvec, LRU_ACTIVE_FILE) + + get_lru_size(lruvec, LRU_INACTIVE_FILE); + spin_lock_irq(&zone->lru_lock); if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { reclaim_stat->recent_scanned[0] /= 2; -- 2.20.1