From ac636e6543309679b39895b2862907a86eda25ac Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Sat, 10 Sep 2016 20:34:05 +1000 Subject: [PATCH] mm, compaction: add the ultimate direct compaction priority During reclaim/compaction loop, it's desirable to get a final answer from unsuccessful compaction so we can either fail the allocation or invoke the OOM killer. However, heuristics such as deferred compaction or pageblock skip bits can cause compaction to skip parts or whole zones and lead to premature OOM's, failures or excessive reclaim/compaction retries. To remedy this, we introduce a new direct compaction priority called COMPACT_PRIO_SYNC_FULL, which instructs direct compaction to: - ignore deferred compaction status for a zone - ignore pageblock skip hints - ignore cached scanner positions and scan the whole zone The new priority should get eventually picked up by should_compact_retry() and this should improve success rates for costly allocations using __GFP_REPEAT, such as hugetlbfs allocations, and reduce some corner-case OOM's for non-costly allocations. Link: http://lkml.kernel.org/r/20160810091226.6709-6-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko Cc: Mel Gorman Cc: Joonsoo Kim Cc: David Rientjes Cc: Rik van Riel Signed-off-by: Andrew Morton --- include/linux/compaction.h | 3 ++- mm/compaction.c | 5 ++++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/linux/compaction.h b/include/linux/compaction.h index e88c037afe47..a1fba9994728 100644 --- a/include/linux/compaction.h +++ b/include/linux/compaction.h @@ -6,8 +6,9 @@ * Lower value means higher priority, analogically to reclaim priority. */ enum compact_priority { + COMPACT_PRIO_SYNC_FULL, + MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL, COMPACT_PRIO_SYNC_LIGHT, - MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT, DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT, COMPACT_PRIO_ASYNC, INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC diff --git a/mm/compaction.c b/mm/compaction.c index 2e1113ff7a03..342fa9e3127a 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1644,6 +1644,8 @@ static enum compact_result compact_zone_order(struct zone *zone, int order, .alloc_flags = alloc_flags, .classzone_idx = classzone_idx, .direct_compaction = true, + .whole_zone = (prio == COMPACT_PRIO_SYNC_FULL), + .ignore_skip_hint = (prio == COMPACT_PRIO_SYNC_FULL) }; INIT_LIST_HEAD(&cc.freepages); INIT_LIST_HEAD(&cc.migratepages); @@ -1689,7 +1691,8 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, ac->nodemask) { enum compact_result status; - if (compaction_deferred(zone, order)) { + if (prio > COMPACT_PRIO_SYNC_FULL + && compaction_deferred(zone, order)) { rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); continue; } -- 2.34.1