[PATCH 12/13] Be more agressive about stealing when MIGRATE_RECLAIMABLE allocations fallback

[Mel Gorman]

Subject: Be more agressive about stealing when MIGRATE_RECLAIMABLE allocations fallback

MIGRATE_RECLAIMABLE allocations tend to be very bursty in nature like when
updatedb starts.  It is likely this will occur in situations where MAX_ORDER
blocks of pages are not free.  This means that updatedb can scatter
MIGRATE_RECLAIMABLE pages throughout the address space.  This patch is more
agressive about stealing blocks of pages for MIGRATE_RECLAIMABLE.

Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/page_alloc.c |   23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.23-rc5-011-bias-the-placement-of-kernel-pages-at-lower-pfns/mm/page_alloc.c linux-2.6.23-rc5-012-be-more-agressive-about-stealing-when-migrate_reclaimable-allocations-fallback/mm/page_alloc.c
--- linux-2.6.23-rc5-011-bias-the-placement-of-kernel-pages-at-lower-pfns/mm/page_alloc.c	2007-09-02 16:22:27.000000000 +0100
+++ linux-2.6.23-rc5-012-be-more-agressive-about-stealing-when-migrate_reclaimable-allocations-fallback/mm/page_alloc.c	2007-09-02 16:22:47.000000000 +0100
@@ -713,7 +713,7 @@ int move_freepages(struct zone *zone,
 {
 	struct page *page;
 	unsigned long order;
-	int blocks_moved = 0;
+	int pages_moved = 0;
 
 #ifndef CONFIG_HOLES_IN_ZONE
 	/*
@@ -742,10 +742,10 @@ int move_freepages(struct zone *zone,
 		list_add(&page->lru,
 			&zone->free_area[order].free_list[migratetype]);
 		page += 1 << order;
-		blocks_moved++;
+		pages_moved += 1 << order;
 	}
 
-	return blocks_moved;
+	return pages_moved;
 }
 
 int move_freepages_block(struct zone *zone, struct page *page, int migratetype)
@@ -817,11 +817,22 @@ static struct page *__rmqueue_fallback(s
 
 			/*
 			 * If breaking a large block of pages, move all free
-			 * pages to the preferred allocation list
+			 * pages to the preferred allocation list. If falling
+			 * back for a reclaimable kernel allocation, be more
+			 * agressive about taking ownership of free pages
 			 */
-			if (unlikely(current_order >= (pageblock_order >> 1)))
+			if (unlikely(current_order >= (pageblock_order >> 1)) ||
+					start_migratetype == MIGRATE_RECLAIMABLE) {
+				unsigned long pages;
+				pages = move_freepages_block(zone, page,
+								start_migratetype);
+
+				/* Claim the whole block if over half of it is free */
+				if (pages >= (1 << (pageblock_order-1)))
+					set_pageblock_migratetype(page,
+								start_migratetype);
+
 				migratetype = start_migratetype;
-				move_freepages_block(zone, page, migratetype);
 			}
 
 			/* Remove the page from the freelists */
-
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