The patch titled
Subject: mm/migrate.c: migrate PG_readahead flag
has been added to the -mm tree. Its filename is
mm-migratec-migrate-pg_readahead-flag.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-migratec-migrate-pg_readahead-flag.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-migratec-migrate-pg_readahead-flag.patch
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------------------------------------------------------
From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Subject: mm/migrate.c: migrate PG_readahead flag
Currently the migration code doesn't migrate PG_readahead flag.
Theoretically this would incur slight performance loss as the application
might have to ramp its readahead back up again. Even though such problem
happens, it might be hidden by something else since migration is typically
triggered by compaction and NUMA balancing, any of which should be more
noticeable.
Migrate the flag after end_page_writeback() since it may clear PG_reclaim
flag, which is the same bit as PG_readahead, for the new page.
Link: http://lkml.kernel.org/r/1581640185-95731-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/migrate.c~mm-migratec-migrate-pg_readahead-flag
+++ a/mm/migrate.c
@@ -647,6 +647,14 @@ void migrate_page_states(struct page *ne
if (PageWriteback(newpage))
end_page_writeback(newpage);
+ /*
+ * PG_readahead share the same bit with PG_reclaim, the above
+ * end_page_writeback() may clear PG_readahead mistakenly, so set
+ * the bit after that.
+ */
+ if (PageReadahead(page))
+ SetPageReadahead(newpage);
+
copy_page_owner(page, newpage);
mem_cgroup_migrate(page, newpage);
_
Patches currently in -mm which might be from yang.shi@xxxxxxxxxxxxxxxxx are
mm-vmpressure-dont-need-call-kfree-if-kstrndup-fails.patch
mm-vmpressure-use-mem_cgroup_is_root-api.patch
mm-migratec-migrate-pg_readahead-flag.patch
