linux-kernel - [PATCH] mm: vmscan: fix malused nr

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Date:	Sat, 21 Jan 2012 22:41:59 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	linux-mm@...ck.org
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Hillf Danton <dhillf@...il.com>
Subject: [PATCH] mm: vmscan: fix malused nr_reclaimed in shrinking zone

The value of nr_reclaimed is the amount of pages reclaimed in the current round,
whereas nr_to_reclaim shoud be compared with the amount of pages
reclaimed in all
rounds, so we have to buffer the pages reclaimed in the past rounds for correct
comparison.

Signed-off-by: Hillf Danton <dhillf@...il.com>
---

--- a/mm/vmscan.c	Sat Jan 14 14:02:20 2012
+++ b/mm/vmscan.c	Sat Jan 21 22:23:48 2012
@@ -2081,13 +2081,15 @@ static void shrink_mem_cgroup_zone(int p
 				   struct scan_control *sc)
 {
 	unsigned long nr[NR_LRU_LISTS];
+	unsigned long reclaimed = 0;
 	unsigned long nr_to_scan;
 	enum lru_list lru;
-	unsigned long nr_reclaimed, nr_scanned;
+	unsigned long nr_reclaimed = 0, nr_scanned;
 	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
 	struct blk_plug plug;

 restart:
+	reclaimed += nr_reclaimed;
 	nr_reclaimed = 0;
 	nr_scanned = sc->nr_scanned;
 	get_scan_count(mz, sc, nr, priority);
@@ -2113,7 +2115,8 @@ restart:
 		 * with multiple processes reclaiming pages, the total
 		 * freeing target can get unreasonably large.
 		 */
-		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
+		if ((nr_reclaimed + reclaimed) >= nr_to_reclaim &&
+					priority < DEF_PRIORITY)
 			break;
 	}
 	blk_finish_plug(&plug);
--
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