From efe771c7603bc524425070d651e70e9c56c57f28 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 5 Mar 2019 15:44:46 -0800 Subject: mm, compaction: always finish scanning of a full pageblock When compaction is finishing, it uses a flag to ensure the pageblock is complete but it makes sense to always complete migration of a pageblock. Minimally, skip information is based on a pageblock and partially scanned pageblocks may incur more scanning in the future. The pageblock skip handling also becomes more strict later in the series and the hint is more useful if a complete pageblock was always scanned. The potentially impacts latency as more scanning is done but it's not a consistent win or loss as the scanning is not always a high percentage of the pageblock and sometimes it is offset by future reductions in scanning. Hence, the results are not presented this time due to a misleading mix of gains/losses without any clear pattern. However, full scanning of the pageblock is important for later patches. Link: http://lkml.kernel.org/r/20190118175136.31341-8-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 --- mm/compaction.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) (limited to 'mm/compaction.c') diff --git a/mm/compaction.c b/mm/compaction.c index 32a88b49f973..3d11c209614a 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1331,16 +1331,14 @@ static enum compact_result __compact_finished(struct compact_control *cc) if (is_via_compact_memory(cc->order)) return COMPACT_CONTINUE; - if (cc->finishing_block) { - /* - * We have finished the pageblock, but better check again that - * we really succeeded. - */ - if (IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages)) - cc->finishing_block = false; - else - return COMPACT_CONTINUE; - } + /* + * Always finish scanning a pageblock to reduce the possibility of + * fallbacks in the future. This is particularly important when + * migration source is unmovable/reclaimable but it's not worth + * special casing. + */ + if (!IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages)) + return COMPACT_CONTINUE; /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { @@ -1382,7 +1380,6 @@ static enum compact_result __compact_finished(struct compact_control *cc) return COMPACT_SUCCESS; } - cc->finishing_block = true; return COMPACT_CONTINUE; } } -- cgit v1.2.3-70-g09d2