From a9e7073514a4d4189ded944fcb475fb6b8b826b8 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 5 Mar 2019 15:45:18 -0800 Subject: [PATCH] mm, compaction: keep cached migration PFNs synced for unusable pageblocks to #26255339 commit 8854c55f54bcc104e3adae42abe16948286ec75c upstream Migrate has separate cached PFNs for ASYNC and SYNC* migration on the basis that some migrations will fail in ASYNC mode. However, if the cached PFNs match at the start of scanning and pageblocks are skipped due to having no isolation candidates, then the sync state does not matter. This patch keeps matching cached PFNs in sync until a pageblock with isolation candidates is found. The actual benefit is marginal given that the sync scanner following the async scanner will often skip a number of pageblocks but it's useless work. Any benefit depends heavily on whether the scanners restarted recently. Link: http://lkml.kernel.org/r/20190118175136.31341-16-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/compaction.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/mm/compaction.c b/mm/compaction.c index c7beb2a1b728..0cfb6ebdcda4 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1971,6 +1971,7 @@ static enum compact_result compact_zone(struct compact_control *cc) unsigned long end_pfn = zone_end_pfn(cc->zone); unsigned long last_migrated_pfn; const bool sync = cc->mode != MIGRATE_ASYNC; + bool update_cached; cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask); ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags, @@ -2018,6 +2019,17 @@ static enum compact_result compact_zone(struct compact_control *cc) last_migrated_pfn = 0; + /* + * Migrate has separate cached PFNs for ASYNC and SYNC* migration on + * the basis that some migrations will fail in ASYNC mode. However, + * if the cached PFNs match and pageblocks are skipped due to having + * no isolation candidates, then the sync state does not matter. + * Until a pageblock with isolation candidates is found, keep the + * cached PFNs in sync to avoid revisiting the same blocks. + */ + update_cached = !sync && + cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1]; + trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, cc->free_pfn, end_pfn, sync); @@ -2049,6 +2061,11 @@ static enum compact_result compact_zone(struct compact_control *cc) last_migrated_pfn = 0; goto out; case ISOLATE_NONE: + if (update_cached) { + cc->zone->compact_cached_migrate_pfn[1] = + cc->zone->compact_cached_migrate_pfn[0]; + } + /* * We haven't isolated and migrated anything, but * there might still be unflushed migrations from @@ -2056,6 +2073,7 @@ static enum compact_result compact_zone(struct compact_control *cc) */ goto check_drain; case ISOLATE_SUCCESS: + update_cached = false; last_migrated_pfn = start_pfn; ; } -- GitLab