+ mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Date: Wed Jul 13 14:20:09 2022 +0800
has been added to the -mm mm-unstable branch.  Its filename is
     mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------

Frm: Chuyi Zhou <zhouchuyi@bytedance.com>
Date: Wed Jul 13 14:20:09 2022 +0800
Subject: mm/compaction: fix set skip in fast_find_migrateblock

(akpm: this is a reapplication of 7efc3b726103, after Mel's "Fix excessive
CPU usage during compaction" series addressed issues whcih this patch
originally exposed).

When we successfully find a pageblock in fast_find_migrateblock(), the
block will be set skip-flag through set_pageblock_skip().  However, when
entering isolate_migratepages_block(), the whole pageblock will be skipped
due to the branch 'if (!valid_page && IS_ALIGNED(low_pfn,
pageblock_nr_pages))'.  Eventually we will goto isolate_abort and isolate
nothing.  That makes fast_find_migrateblock useless.

In this patch, when we find a suitable pageblock in
fast_find_migrateblock, we do noting but let isolate_migratepages_block to
set skip flag to the pageblock after scan it.  Normally, we would isolate
some pages from the fast-find block.

I use mmtest/thpscale-madvhugepage test it. Here is the result:
                            baseline               patch
Amean     fault-both-1      1331.66 (   0.00%)     1261.04 *   5.30%*
Amean     fault-both-3      1383.95 (   0.00%)     1191.69 *  13.89%*
Amean     fault-both-5      1568.13 (   0.00%)     1445.20 *   7.84%*
Amean     fault-both-7      1819.62 (   0.00%)     1555.13 *  14.54%*
Amean     fault-both-12     1106.96 (   0.00%)     1149.43 *  -3.84%*
Amean     fault-both-18     2196.93 (   0.00%)     1875.77 *  14.62%*
Amean     fault-both-24     2642.69 (   0.00%)     2671.21 *  -1.08%*
Amean     fault-both-30     2901.89 (   0.00%)     2857.32 *   1.54%*
Amean     fault-both-32     3747.00 (   0.00%)     3479.23 *   7.15%*

Link: https://lkml.kernel.org/r/20220713062009.597255-1-zhouchuyi@bytedance.com
Fixes: 70b44595eafe9 ("mm, compaction: use free lists to quickly locate a migration source")
Signed-off-by: zhouchuyi <zhouchuyi@bytedance.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/compaction.c~mm-compaction-fix-set-skip-in-fast_find_migrateblock
+++ a/mm/compaction.c
@@ -1845,7 +1845,6 @@ static unsigned long fast_find_migratebl
 					pfn = cc->zone->zone_start_pfn;
 				cc->fast_search_fail = 0;
 				found_block = true;
-				set_pageblock_skip(freepage);
 				break;
 			}
 		}
_

Patches currently in -mm which might be from zhouchuyi@bytedance.com are