path: root/mm/page_alloc.c
diff options
authorMel Gorman <>2009-09-21 17:02:31 -0700
committerLinus Torvalds <>2009-09-22 07:17:33 -0700
commit2f66a68f3fac2e94da360c342ff78ab45553f86c (patch)
treeec8de9c7d18d866e63e2c9bcbecf902896b687bd /mm/page_alloc.c
parentfe1ff49d0d1c30254dbfc84c3786eb538e0cc7d1 (diff)
page-allocator: change migratetype for all pageblocks within a high-order page during __rmqueue_fallback
When there are no pages of a target migratetype free, the page allocator selects a high-order block of another migratetype to allocate from. When the order of the page taken is greater than pageblock_order, all pageblocks within that high-order page should change migratetype so that pages are later freed to the correct free-lists. The current behaviour is that pageblocks change migratetype if the order being split matches the pageblock_order. When pageblock_order < MAX_ORDER-1, ownership is not changing correct and pages are being later freed to the incorrect list and this impacts fragmentation avoidance. This patch changes all pageblocks within the high-order page being split to the correct migratetype. Without the patch, allocation success rates for hugepages under stress were about 59% of physical memory on x86-64. With the patch applied, this goes up to 65%. Signed-off-by: Mel Gorman <> Cc: Andy Whitcroft <> Cc: KOSAKI Motohiro <> Cc: KAMEZAWA Hiroyuki <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/page_alloc.c')
1 files changed, 14 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9242d13f4ff..20759803a64 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -783,6 +783,17 @@ static int move_freepages_block(struct zone *zone, struct page *page,
return move_freepages(zone, start_page, end_page, migratetype);
+static void change_pageblock_range(struct page *pageblock_page,
+ int start_order, int migratetype)
+ int nr_pageblocks = 1 << (start_order - pageblock_order);
+ while (nr_pageblocks--) {
+ set_pageblock_migratetype(pageblock_page, migratetype);
+ pageblock_page += pageblock_nr_pages;
+ }
/* Remove an element from the buddy allocator from the fallback list */
static inline struct page *
__rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
@@ -836,8 +847,9 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
- if (current_order == pageblock_order)
- set_pageblock_migratetype(page,
+ /* Take ownership for orders >= pageblock_order */
+ if (current_order >= pageblock_order)
+ change_pageblock_range(page, current_order,
expand(zone, page, order, current_order, area, migratetype);