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mm/migrate.c: migrate PG_readahead flag

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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.

[akpm@linux-foundation.org: tweak comment]
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Link: http://lkml.kernel.org/r/1581640185-95731-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yang Shi 2020-04-06 20:04:21 -07:00 committed by Linus Torvalds
parent d08221a080
commit 6aeff241fe
1 changed files with 8 additions and 0 deletions
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8
mm/migrate.c
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@ -647,6 +647,14 @@ void migrate_page_states(struct page *newpage, struct page *page)
if (PageWriteback(newpage))
end_page_writeback(newpage);
/*
* PG_readahead shares 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);