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authorMel Gorman <mel@csn.ul.ie>2011-01-13 15:45:59 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:34 -0800
commit9927af740b1b9b1e769310bd0b91425e8047b803 (patch)
tree5195dfbe36ece987f7e3d7c04b87327a20b16ea6
parent7f0f24967b0349798803260b2e4bf347cffa1990 (diff)
mm: compaction: perform a faster migration scan when migrating asynchronously
try_to_compact_pages() is initially called to only migrate pages asychronously and kswapd always compacts asynchronously. Both are being optimistic so it is important to complete the work as quickly as possible to minimise stalls. This patch alters the scanner when asynchronous to only consider MIGRATE_MOVABLE pageblocks as migration candidates. This reduces stalls when allocating huge pages while not impairing allocation success rates as a full scan will be performed if necessary after direct reclaim. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/compaction.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index e005a30e968..b0fbfdfad29 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -240,6 +240,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
struct compact_control *cc)
{
unsigned long low_pfn, end_pfn;
+ unsigned long last_pageblock_nr = 0, pageblock_nr;
unsigned long nr_scanned = 0, nr_isolated = 0;
struct list_head *migratelist = &cc->migratepages;
@@ -280,6 +281,20 @@ static unsigned long isolate_migratepages(struct zone *zone,
if (PageBuddy(page))
continue;
+ /*
+ * For async migration, also only scan in MOVABLE blocks. Async
+ * migration is optimistic to see if the minimum amount of work
+ * satisfies the allocation
+ */
+ pageblock_nr = low_pfn >> pageblock_order;
+ if (!cc->sync && last_pageblock_nr != pageblock_nr &&
+ get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
+ low_pfn += pageblock_nr_pages;
+ low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
+ last_pageblock_nr = pageblock_nr;
+ continue;
+ }
+
/* Try isolate the page */
if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
continue;