From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Sat, 16 Jan 2010 01:01:25 +0000 (-0800)
Subject: vmscan: kswapd: don't retry balance_pgdat() if all zones are unreclaimable
X-Git-Tag: v2.6.33-rc5~44
X-Git-Url: http://bbs.cooldavid.org/git/?a=commitdiff_plain;h=de3fab39348dff18c69a0cd04efee9c276a02f51;p=net-next-2.6.git

vmscan: kswapd: don't retry balance_pgdat() if all zones are unreclaimable

Commit f50de2d3 (vmscan: have kswapd sleep for a short interval and double
check it should be asleep) can cause kswapd to enter an infinite loop if
running on a single-CPU system.  If all zones are unreclaimble,
sleeping_prematurely return 1 and kswapd will call balance_pgdat() again.
but it's totally meaningless, balance_pgdat() doesn't anything against
unreclaimable zone!

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Reported-by: Will Newton <will.newton@gmail.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Tested-by: Will Newton <will.newton@gmail.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 885207a6b6b..c26986c85ce 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1922,6 +1922,9 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
 		if (!populated_zone(zone))
 			continue;
 
+		if (zone_is_all_unreclaimable(zone))
+			continue;
+
 		if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
 								0, 0))
 			return 1;