mm/cma: change fallback behaviour for CMA freepage (dc67647b) · Commits · 戴 / test

Freepage with MIGRATE_CMA can be used only for MIGRATE_MOVABLE and they should not be expanded to other migratetype buddy list to protect them from unmovable/reclaimable allocation. Implementing these requirements in __rmqueue_fallback(), that is, finding largest possible block of freepage has bad effect that high order freepage with MIGRATE_CMA are broken continually although there are suitable order CMA freepage. Reason is that they are not be expanded to other migratetype buddy list and next __rmqueue_fallback() invocation try to finds another largest block of freepage and break it again. So, MIGRATE_CMA fallback should be handled separately. This patch introduces __rmqueue_cma_fallback(), that just wrapper of __rmqueue_smallest() and call it before __rmqueue_fallback() if migratetype == MIGRATE_MOVABLE. This results in unintended behaviour change that MIGRATE_CMA freepage is always used first rather than other migratetype as movable allocation's fallback. But, as already mentioned above, MIGRATE_CMA can be used only for MIGRATE_MOVABLE, so it is better to use MIGRATE_CMA freepage first as much as possible. Otherwise, we needlessly take up precious freepages with other migratetype and increase chance of fragmentation. Signed-off-by:

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

Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Signed-off-by:

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

Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

+19 −17

Original line number	Diff line number	Diff line
		@@ -1032,11 +1032,9 @@ struct page __rmqueue_smallest(struct zone zone, unsigned int order,
		static int fallbacks[MIGRATE_TYPES][4] = {
		[MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
		[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
		[MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
		#ifdef CONFIG_CMA
		[MIGRATE_MOVABLE] = { MIGRATE_CMA, MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
		[MIGRATE_CMA] = { MIGRATE_RESERVE }, /* Never used */
		#else
		[MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
		#endif
		[MIGRATE_RESERVE] = { MIGRATE_RESERVE }, /* Never used */
		#ifdef CONFIG_MEMORY_ISOLATION
		@@ -1044,6 +1042,17 @@ static int fallbacks[MIGRATE_TYPES][4] = {
		#endif
		};

		#ifdef CONFIG_CMA
		static struct page __rmqueue_cma_fallback(struct zone zone,
		unsigned int order)
		{
		return __rmqueue_smallest(zone, order, MIGRATE_CMA);
		}
		#else
		static inline struct page __rmqueue_cma_fallback(struct zone zone,
		unsigned int order) { return NULL; }
		#endif

		/*
		* Move the free pages in a range to the free lists of the requested type.
		* Note that start_page and end_pages are not aligned on a pageblock
		@@ -1195,19 +1204,8 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
		struct page, lru);
		area->nr_free--;

		if (!is_migrate_cma(migratetype)) {
		try_to_steal_freepages(zone, page,
		start_migratetype,
		try_to_steal_freepages(zone, page, start_migratetype,
		migratetype);
		} else {
		/*
		* When borrowing from MIGRATE_CMA, we need to
		* release the excess buddy pages to CMA
		* itself, and we do not try to steal extra
		* free pages.
		*/
		buddy_type = migratetype;
		}

		/* Remove the page from the freelists */
		list_del(&page->lru);
		@@ -1249,6 +1247,10 @@ retry_reserve:
		page = __rmqueue_smallest(zone, order, migratetype);

		if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
		if (migratetype == MIGRATE_MOVABLE)
		page = __rmqueue_cma_fallback(zone, order);

		if (!page)
		page = __rmqueue_fallback(zone, order, migratetype);

		/*

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