From d943649831aba0fcdda37a0e9e25b332a634cf5e Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Fri, 7 Oct 2016 17:00:31 -0700 Subject: [PATCH] mm, compaction: more reliably increase direct compaction priority During reclaim/compaction loop, compaction priority can be increased by the should_compact_retry() function, but the current code is not optimal. Priority is only increased when compaction_failed() is true, which means that compaction has scanned the whole zone. This may not happen even after multiple attempts with a lower priority due to parallel activity, so we might needlessly struggle on the lower priorities and possibly run out of compaction retry attempts in the process. After this patch we are guaranteed at least one attempt at the highest compaction priority even if we exhaust all retries at the lower priorities. Link: http://lkml.kernel.org/r/20160906135258.18335-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka Cc: Michal Hocko Cc: Mel Gorman Cc: Joonsoo Kim Cc: David Rientjes Cc: Rik van Riel Cc: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 33 +++++++++++++++++++-------------- 1 file changed, 19 insertions(+), 14 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 634806f55120..a8703b592c39 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3160,25 +3160,23 @@ static inline bool should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, enum compact_result compact_result, enum compact_priority *compact_priority, - int compaction_retries) + int *compaction_retries) { int max_retries = MAX_COMPACT_RETRIES; if (!order) return false; + if (compaction_made_progress(compact_result)) + (*compaction_retries)++; + /* * compaction considers all the zone as desperately out of memory * so it doesn't really make much sense to retry except when the * failure could be caused by insufficient priority */ - if (compaction_failed(compact_result)) { - if (*compact_priority > MIN_COMPACT_PRIORITY) { - (*compact_priority)--; - return true; - } - return false; - } + if (compaction_failed(compact_result)) + goto check_priority; /* * make sure the compaction wasn't deferred or didn't bail out early @@ -3199,9 +3197,19 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, */ if (order > PAGE_ALLOC_COSTLY_ORDER) max_retries /= 4; - if (compaction_retries <= max_retries) + if (*compaction_retries <= max_retries) return true; + /* + * Make sure there are attempts at the highest priority if we exhausted + * all retries or failed at the lower priorities. + */ +check_priority: + if (*compact_priority > MIN_COMPACT_PRIORITY) { + (*compact_priority)--; + *compaction_retries = 0; + return true; + } return false; } #else @@ -3218,7 +3226,7 @@ static inline bool should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags, enum compact_result compact_result, enum compact_priority *compact_priority, - int compaction_retries) + int *compaction_retries) { struct zone *zone; struct zoneref *z; @@ -3620,9 +3628,6 @@ retry: if (page) goto got_pg; - if (order && compaction_made_progress(compact_result)) - compaction_retries++; - /* Do not loop if specifically requested */ if (gfp_mask & __GFP_NORETRY) goto nopage; @@ -3657,7 +3662,7 @@ retry: if (did_some_progress > 0 && should_compact_retry(ac, order, alloc_flags, compact_result, &compact_priority, - compaction_retries)) + &compaction_retries)) goto retry; /* Reclaim has failed us, start killing things */ -- 2.20.1