From e332f741a8dd1ec9a6dc8aa997296ecbfe64323e Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 5 Mar 2019 15:45:38 -0800 Subject: mm, compaction: be selective about what pageblocks to clear skip hints Pageblock hints are cleared when compaction restarts or kswapd makes enough progress that it can sleep but it's over-eager in that the bit is cleared for migration sources with no LRU pages and migration targets with no free pages. As pageblock skip hint flushes are relatively rare and out-of-band with respect to kswapd, this patch makes a few more expensive checks to see if it's appropriate to even clear the bit. Every pageblock that is not cleared will avoid 512 pages being scanned unnecessarily on x86-64. The impact is variable with different workloads showing small differences in latency, success rates and scan rates. This is expected as clearing the hints is not that common but doing a small amount of work out-of-band to avoid a large amount of work in-band later is generally a good thing. Link: http://lkml.kernel.org/r/20190118175136.31341-22-mgorman@techsingularity.net Signed-off-by: Mel Gorman Signed-off-by: Qian Cai Acked-by: Vlastimil Babka Cc: Andrea Arcangeli Cc: Dan Carpenter Cc: David Rientjes Cc: YueHaibing [cai@lca.pw: no stuck in __reset_isolation_pfn()] Link: http://lkml.kernel.org/r/20190206034732.75687-1-cai@lca.pw Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmzone.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 842f9189537b..90c13cdeefb5 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -480,6 +480,8 @@ struct zone { unsigned long compact_cached_free_pfn; /* pfn where async and sync compaction migration scanner should start */ unsigned long compact_cached_migrate_pfn[2]; + unsigned long compact_init_migrate_pfn; + unsigned long compact_init_free_pfn; #endif #ifdef CONFIG_COMPACTION -- cgit v1.2.3