The patch titled Subject: mm/compaction: fix 'limit' in fast_isolate_freepages has been added to the -mm tree. Its filename is mm-compaction-fix-limit-in-fast_isolate_freepages.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-fix-limit-in-fast_isolate_freepages.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-fix-limit-in-fast_isolate_freepages.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Wonhyuk Yang <vvghjk1234@xxxxxxxxx> Subject: mm/compaction: fix 'limit' in fast_isolate_freepages Because of 'min(1, ...)', fast_isolate_freepages set 'limit' to 0 or 1. This takes away the opportunities of find candinate pages. So, by making enough scans available, increases the probability of finding the appropriate freepage. Tested it on the thpscale and the results are as follows. 5.12.0 5.12.0 valnilla patched Amean fault-both-1 598.15 ( 0.00%) 592.56 ( 0.93%) Amean fault-both-3 1494.47 ( 0.00%) 1514.35 ( -1.33%) Amean fault-both-5 2519.48 ( 0.00%) 2471.76 ( 1.89%) Amean fault-both-7 3173.85 ( 0.00%) 3079.19 ( 2.98%) Amean fault-both-12 8063.83 ( 0.00%) 7858.29 ( 2.55%) Amean fault-both-18 8781.20 ( 0.00%) 7827.70 * 10.86%* Amean fault-both-24 12576.44 ( 0.00%) 12250.20 ( 2.59%) Amean fault-both-30 18503.27 ( 0.00%) 17528.11 * 5.27%* Amean fault-both-32 16133.69 ( 0.00%) 13874.24 * 14.00%* 5.12.0 5.12.0 vanilla patched Ops Compaction migrate scanned 6547133.00 5963901.00 Ops Compaction free scanned 32452453.00 26609101.00 5.12 5.12 vanilla patched Duration User 27.99 28.84 Duration System 244.08 236.76 Duration Elapsed 78.27 78.38 Link: https://lkml.kernel.org/r/20210626082443.22547-1-vvghjk1234@xxxxxxxxx Fixes: 5a811889de10f ("mm, compaction: use free lists to quickly locate a migration target") Signed-off-by: Wonhyuk Yang <vvghjk1234@xxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/mm/compaction.c~mm-compaction-fix-limit-in-fast_isolate_freepages +++ a/mm/compaction.c @@ -1378,7 +1378,7 @@ static int next_search_order(struct comp static unsigned long fast_isolate_freepages(struct compact_control *cc) { - unsigned int limit = min(1U, freelist_scan_limit(cc) >> 1); + unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1); unsigned int nr_scanned = 0; unsigned long low_pfn, min_pfn, highest = 0; unsigned long nr_isolated = 0; @@ -1490,11 +1490,11 @@ fast_isolate_freepages(struct compact_co spin_unlock_irqrestore(&cc->zone->lock, flags); /* - * Smaller scan on next order so the total scan ig related + * Smaller scan on next order so the total scan is related * to freelist_scan_limit. */ if (order_scanned >= limit) - limit = min(1U, limit >> 1); + limit = max(1U, limit >> 1); } if (!page) { _ Patches currently in -mm which might be from vvghjk1234@xxxxxxxxx are mm-compaction-fix-limit-in-fast_isolate_freepages.patch