From cc5c9f098fe48a8736add8a23c983524ca16cea5 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Fri, 7 Oct 2016 17:00:43 -0700 Subject: [PATCH] mm, compaction: ignore fragindex from compaction_zonelist_suitable() The compaction_zonelist_suitable() function tries to determine if compaction will be able to proceed after sufficient reclaim, i.e. whether there are enough reclaimable pages to provide enough order-0 freepages for compaction. This addition of reclaimable pages to the free pages works well for the order-0 watermark check, but in the fragmentation index check we only consider truly free pages. Thus we can get fragindex value close to 0 which indicates failure do to lack of memory, and wrongly decide that compaction won't be suitable even after reclaim. Instead of trying to somehow adjust fragindex for reclaimable pages, let's just skip it from compaction_zonelist_suitable(). Link: http://lkml.kernel.org/r/20160926162025.21555-4-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 Signed-off-by: Linus Torvalds --- mm/compaction.c | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 86d4d0bbfc7c..b918bdb28aed 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1379,7 +1379,6 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order, int classzone_idx, unsigned long wmark_target) { - int fragindex; unsigned long watermark; if (is_via_compact_memory(order)) @@ -1415,6 +1414,18 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order, ALLOC_CMA, wmark_target)) return COMPACT_SKIPPED; + return COMPACT_CONTINUE; +} + +enum compact_result compaction_suitable(struct zone *zone, int order, + unsigned int alloc_flags, + int classzone_idx) +{ + enum compact_result ret; + int fragindex; + + ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx, + zone_page_state(zone, NR_FREE_PAGES)); /* * fragmentation index determines if allocation failures are due to * low memory or external fragmentation @@ -1426,21 +1437,12 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order, * * Only compact if a failure would be due to fragmentation. */ - fragindex = fragmentation_index(zone, order); - if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) - return COMPACT_NOT_SUITABLE_ZONE; - - return COMPACT_CONTINUE; -} - -enum compact_result compaction_suitable(struct zone *zone, int order, - unsigned int alloc_flags, - int classzone_idx) -{ - enum compact_result ret; + if (ret == COMPACT_CONTINUE) { + fragindex = fragmentation_index(zone, order); + if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) + ret = COMPACT_NOT_SUITABLE_ZONE; + } - ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx, - zone_page_state(zone, NR_FREE_PAGES)); trace_mm_compaction_suitable(zone, order, ret); if (ret == COMPACT_NOT_SUITABLE_ZONE) ret = COMPACT_SKIPPED; @@ -1473,8 +1475,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, available += zone_page_state_snapshot(zone, NR_FREE_PAGES); compact_result = __compaction_suitable(zone, order, alloc_flags, ac_classzone_idx(ac), available); - if (compact_result != COMPACT_SKIPPED && - compact_result != COMPACT_NOT_SUITABLE_ZONE) + if (compact_result != COMPACT_SKIPPED) return true; } -- 2.20.1