[merged mm-stable] mm-compaction-ensure-rescanning-only-happens-on-partially-scanned-pageblocks.patch removed from -mm tree

[merged mm-stable] mm-compaction-ensure-rescanning-only-happens-on-partially-scanned-pageblocks.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: compaction: ensure rescanning only happens on partially scanned pageblocks
has been removed from the -mm tree.  Its filename was
     mm-compaction-ensure-rescanning-only-happens-on-partially-scanned-pageblocks.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Mel Gorman <mgorman@techsingularity.net>
Subject: mm: compaction: ensure rescanning only happens on partially scanned pageblocks
Date: Mon, 15 May 2023 12:33:41 +0100

Patch series "Follow-up "Fix excessive CPU usage during compaction"".

The series "Fix excessive CPU usage during compaction" [1] attempted to
fix a bug [2] but Vlastimil noted that the fix was incomplete [3]. While
the series was merged, fast_find_migrateblock was still disabled. This
series should fix the corner cases and allow 95e7a450b819 ("Revert
"mm/compaction: fix set skip in fast_find_migrateblock"") to be safely
reverted. Details on how many pageblocks are rescanned are in the
changelog of the last patch.

"Raghavendra K T" tested this and reported "decent improvement from perf
perspective as well as compaction related data [4]

[1] https://lore.kernel.org/r/20230125134434.18017-1-mgorman@techsingularity.net
[2] https://bugzilla.suse.com/show_bug.cgi?id=1206848
[3] https://lore.kernel.org/r/a55cf026-a2f9-ef01-9a4c-398693e048ea@suse.cz
[4] https://lkml.kernel.org/r/6d62686f-964d-342c-e085-0eae2555cc54@amd.com


This patch (of 4):
compact_zone() intends to rescan pageblocks if there is a failure to
migrate "within the current order-aligned block".  However, the pageblock
scan may already be complete and moved to the next block causing the next
pageblock to be "rescanned".  Ensure only the most recent pageblock is
rescanned.

Link: https://lkml.kernel.org/r/20230515113344.6869-1-mgorman@techsingularity.net
Link: https://lkml.kernel.org/r/20230515113344.6869-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Raghavendra K T <raghavendra.kt@amd.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Chuyi Zhou <zhouchuyi@bytedance.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/compaction.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/compaction.c~mm-compaction-ensure-rescanning-only-happens-on-partially-scanned-pageblocks
+++ a/mm/compaction.c
@@ -2465,8 +2465,9 @@ rescan:
 			 * fast_find_migrateblock revisiting blocks that were
 			 * recently partially scanned.
 			 */
-			if (cc->direct_compaction && !cc->finish_pageblock &&
-						(cc->mode < MIGRATE_SYNC)) {
+			if (!pageblock_aligned(cc->migrate_pfn) &&
+			    cc->direct_compaction && !cc->finish_pageblock &&
+			    (cc->mode < MIGRATE_SYNC)) {
 				cc->finish_pageblock = true;
 
 				/*
_

Patches currently in -mm which might be from mgorman@techsingularity.net are