From d7f05528eedb047efe2288cff777676b028747b6 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 28 Jul 2016 15:47:37 -0700 Subject: [PATCH] mm, vmscan: account for skipped pages as a partial scan Page reclaim determines whether a pgdat is unreclaimable by examining how many pages have been scanned since a page was freed and comparing that to the LRU sizes. Skipped pages are not reclaim candidates but contribute to scanned. This can prematurely mark a pgdat as unreclaimable and trigger an OOM kill. This patch accounts for skipped pages as a partial scan so that an unreclaimable pgdat will still be marked as such but by scaling the cost of a skip, it'll avoid the pgdat being marked prematurely. Link: http://lkml.kernel.org/r/1469110261-7365-6-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Johannes Weiner Cc: Minchan Kim Cc: Michal Hocko Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index f7b958b9aea9..0294ab34f475 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1424,7 +1424,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, LIST_HEAD(pages_skipped); for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan && - !list_empty(src); scan++) { + !list_empty(src);) { struct page *page; page = lru_to_page(src); @@ -1438,6 +1438,12 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, continue; } + /* + * Account for scanned and skipped separetly to avoid the pgdat + * being prematurely marked unreclaimable by pgdat_reclaimable. + */ + scan++; + switch (__isolate_lru_page(page, mode)) { case 0: nr_pages = hpage_nr_pages(page); @@ -1465,14 +1471,24 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, */ if (!list_empty(&pages_skipped)) { int zid; + unsigned long total_skipped = 0; - list_splice(&pages_skipped, src); for (zid = 0; zid < MAX_NR_ZONES; zid++) { if (!nr_skipped[zid]) continue; __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); + total_skipped += nr_skipped[zid]; } + + /* + * Account skipped pages as a partial scan as the pgdat may be + * close to unreclaimable. If the LRU list is empty, account + * skipped pages as a full scan. + */ + scan += list_empty(src) ? total_skipped : total_skipped >> 2; + + list_splice(&pages_skipped, src); } *nr_scanned = scan; trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, scan, -- 2.20.1