mm/compaction: disallow high-order page for migration target (7d348b9e) · Commits · 戴 / test

Purpose of compaction is to get a high order page. Currently, if we find high-order page while searching migration target page, we break it to order-0 pages and use them as migration target. It is contrary to purpose of compaction, so disallow high-order page to be used for migration target. Additionally, clean-up logic in suitable_migration_target() to simplify the code. There is no functional changes from this clean-up. Signed-off-by:

Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by:

Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

+3 −12

Original line number	Diff line number	Diff line
		@@ -217,21 +217,12 @@ static inline bool compact_trylock_irqsave(spinlock_t *lock,
		/* Returns true if the page is within a block suitable for migration to */
		static bool suitable_migration_target(struct page *page)
		{
		int migratetype = get_pageblock_migratetype(page);

		/* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
		if (migratetype == MIGRATE_RESERVE)
		return false;

		if (is_migrate_isolate(migratetype))
		return false;

		/* If the page is a large free page, then allow migration */
		/* If the page is a large free page, then disallow migration */
		if (PageBuddy(page) && page_order(page) >= pageblock_order)
		return true;
		return false;

		/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
		if (migrate_async_suitable(migratetype))
		if (migrate_async_suitable(get_pageblock_migratetype(page)))
		return true;

		/* Otherwise skip the block */

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