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 <mel@csn.ul.ie>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9242d13..2075980 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -783,6 +783,17 @@
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 @@
list_del(&page->lru);
rmv_page_order(page);
- 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,
start_migratetype);
expand(zone, page, order, current_order, area, migratetype);