From 0db2cb8da89d991762ec2aece45e55ceaee34664 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Tue, 15 Mar 2016 14:57:01 -0700 Subject: [PATCH] mm, vmscan: make zone_reclaimable_pages more precise zone_reclaimable_pages() is used in should_reclaim_retry() which uses it to calculate the target for the watermark check. This means that precise numbers are important for the correct decision. zone_reclaimable_pages uses zone_page_state which can contain stale data with per-cpu diffs not synced yet (the last vmstat_update might have run 1s in the past). Use zone_page_state_snapshot() in zone_reclaimable_pages() instead. None of the current callers is in a hot path where getting the precise value (which involves per-cpu iteration) would cause an unreasonable overhead. Signed-off-by: Michal Hocko Signed-off-by: Tetsuo Handa Suggested-by: David Rientjes Acked-by: David Rientjes Acked-by: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index db5722a07d4f..039f08d369a5 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -195,21 +195,21 @@ static unsigned long zone_reclaimable_pages(struct zone *zone) { unsigned long nr; - nr = zone_page_state(zone, NR_ACTIVE_FILE) + - zone_page_state(zone, NR_INACTIVE_FILE) + - zone_page_state(zone, NR_ISOLATED_FILE); + nr = zone_page_state_snapshot(zone, NR_ACTIVE_FILE) + + zone_page_state_snapshot(zone, NR_INACTIVE_FILE) + + zone_page_state_snapshot(zone, NR_ISOLATED_FILE); if (get_nr_swap_pages() > 0) - nr += zone_page_state(zone, NR_ACTIVE_ANON) + - zone_page_state(zone, NR_INACTIVE_ANON) + - zone_page_state(zone, NR_ISOLATED_ANON); + nr += zone_page_state_snapshot(zone, NR_ACTIVE_ANON) + + zone_page_state_snapshot(zone, NR_INACTIVE_ANON) + + zone_page_state_snapshot(zone, NR_ISOLATED_ANON); return nr; } bool zone_reclaimable(struct zone *zone) { - return zone_page_state(zone, NR_PAGES_SCANNED) < + return zone_page_state_snapshot(zone, NR_PAGES_SCANNED) < zone_reclaimable_pages(zone) * 6; } -- 2.20.1