Commit b02da723 authored Jul 01, 2013 by Laura Abbott Committed by Stephen Boyd Aug 22, 2013

mm: Always split CMA pages



The page allocator (correctly) checks watermarks when determining
if a page should be split to avoid fragmentation. For general
migration, this is acceptable but this may lead to high rates of
CMA failure under memory pressure. Since CMA migration failures
have a very high cost from a user perspective, skip the watermark
checks and always split the page. This may result in more
fragmentation in the zone, but it's worth it given the benefit to
CMA allocations.

Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

parent 2626967e

mm/page_alloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1458,7 +1458,7 @@ static int __isolate_free_page(struct page *page, unsigned int order)
		zone = page_zone(page);
		mt = get_pageblock_migratetype(page);

		if (!is_migrate_isolate(mt)) {
		if (!is_migrate_isolate(mt) && !is_migrate_cma(mt)) {
		/* Obey watermarks as if the page was being allocated */
		watermark = low_wmark_pages(zone) + (1 << order);
		if (!is_migrate_cma(mt) &&