linux-kernel - [PATCH 12/12] Be more agressive about stealing when MIGRATE

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Date:	Thu,  1 Mar 2007 10:06:30 +0000 (GMT)
From:	Mel Gorman <mel@....ul.ie>
To:	akpm@...ux-foundation.org
Cc:	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 12/12] 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@....ul.ie>
---

 page_alloc.c |   18 +++++++++++++++---
 1 files changed, 15 insertions(+), 3 deletions(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.20-mm2-011_biasplacement/mm/page_alloc.c linux-2.6.20-mm2-012_grabbyreclaim/mm/page_alloc.c
--- linux-2.6.20-mm2-011_biasplacement/mm/page_alloc.c	2007-02-20 18:52:18.000000000 +0000
+++ linux-2.6.20-mm2-012_grabbyreclaim/mm/page_alloc.c	2007-02-20 18:54:35.000000000 +0000
@@ -806,11 +806,23 @@ retry:
 
 			/*
 			 * 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 >= MAX_ORDER / 2)) {
+			if (unlikely(current_order >= MAX_ORDER / 2) ||
+					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 << current_order) >= (1 << (MAX_ORDER-2)) &&
+						migratetype != MIGRATE_HIGHATOMIC)
+					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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