From a7ff78ca20046401704d7f2b5d44a44b5c9c9234 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 5 Mar 2019 15:44:50 -0800 Subject: [PATCH 0922/2944] mm, compaction: ignore the fragmentation avoidance boost for isolation and compaction to #26255339 commit fd1444b2729289ea3ef6b6096be604f8983e9f9f upstream When pageblocks get fragmented, watermarks are artifically boosted to reclaim pages to avoid further fragmentation events. However, compaction is often either fragmentation-neutral or moving movable pages away from unmovable/reclaimable pages. As the true watermarks are preserved, allow compaction to ignore the boost factor. The expected impact is very slight as the main benefit is that compaction is slightly more likely to succeed when the system has been fragmented very recently. On both 1-socket and 2-socket machines for THP-intensive allocation during fragmentation the success rate was increased by less than 1% which is marginal. However, detailed tracing indicated that failure of migration due to a premature ENOMEM triggered by watermark checks were eliminated. Link: http://lkml.kernel.org/r/20190118175136.31341-9-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Cc: Andrea Arcangeli Cc: Dan Carpenter Cc: David Rientjes Cc: YueHaibing Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Yang Shi Reviewed-by: Xunlei Pang --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 865d13b..dd6090a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3000,7 +3000,7 @@ int __isolate_free_page(struct page *page, unsigned int order) * watermark, because we already know our high-order page * exists. */ - watermark = min_wmark_pages(zone) + (1UL << order); + watermark = zone->_watermark[WMARK_MIN] + (1UL << order); if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) return 0; -- 1.8.3.1