The patch titled
Subject: mm/migrate: make migrate_pages_batch() stats consistent
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-migrate-make-migrate_pages_batch-stats-consistent.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate-make-migrate_pages_batch-stats-consistent.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm/migrate: make migrate_pages_batch() stats consistent
Date: Tue, 18 Jun 2024 09:41:51 -0400
As Ying pointed out in [1], stats->nr_thp_failed needs to be updated to
avoid stats inconsistency between MIGRATE_SYNC and MIGRATE_ASYNC when
calling migrate_pages_batch().
Because if not, when migrate_pages_batch() is called via
migrate_pages(MIGRATE_ASYNC), nr_thp_failed will not be increased and when
migrate_pages_batch() is called via migrate_pages(MIGRATE_SYNC*),
nr_thp_failed will be increase in migrate_pages_sync() by
stats->nr_thp_failed += astats.nr_thp_split.
[1] https://lore.kernel.org/linux-mm/87msnq7key.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20240620012712.19804-1-zi.yan@xxxxxxxx
Link: https://lkml.kernel.org/r/20240618134151.29214-1-zi.yan@xxxxxxxx
Fixes: 7262f208ca68 ("mm/migrate: split source folio if it is on deferred split list")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Suggested-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/mm/migrate.c~mm-migrate-make-migrate_pages_batch-stats-consistent
+++ a/mm/migrate.c
@@ -1659,6 +1659,10 @@ static int migrate_pages_batch(struct li
* migrate_pages() may report success with (split but
* unmigrated) pages still on its fromlist; whereas it
* always reports success when its fromlist is empty.
+ * stats->nr_thp_failed should be increased too,
+ * otherwise stats inconsistency will happen when
+ * migrate_pages_batch is called via migrate_pages()
+ * with MIGRATE_SYNC and MIGRATE_ASYNC.
*
* Only check it without removing it from the list.
* Since the folio can be on deferred_split_scan()
@@ -1675,6 +1679,7 @@ static int migrate_pages_batch(struct li
!list_empty(&folio->_deferred_list)) {
if (try_split_folio(folio, split_folios) == 0) {
nr_failed++;
+ stats->nr_thp_failed += is_thp;
stats->nr_thp_split += is_thp;
stats->nr_split++;
continue;
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-migrate-make-migrate_pages_batch-stats-consistent.patch
