Commit 6aeff241 authored Apr 06, 2020 by Yang Shi Committed by Linus Torvalds Apr 07, 2020

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.

[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>

parent d08221a0

mm/migrate.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -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);

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