From 355b09c47a0cbb73b3e65a57c03f157f2e7ddb0b Mon Sep 17 00:00:00 2001
From: Mel Gorman <mel@csn.ul.ie>
Date: Thu, 13 Jan 2011 15:46:24 -0800
Subject: [PATCH] mm: kswapd: treat zone->all_unreclaimable in
 sleeping_prematurely similar to balance_pgdat()

After DEF_PRIORITY, balance_pgdat() considers all_unreclaimable zones to
be balanced but sleeping_prematurely does not.  This can force kswapd to
stay awake longer than it should.  This patch fixes it.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Eric B Munson <emunson@mgebm.net>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Simon Kirby <sim@hostway.ca>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/vmscan.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index dafb9d9..388a044 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2244,8 +2244,16 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
 		if (!populated_zone(zone))
 			continue;
 
-		if (zone->all_unreclaimable)
+		/*
+		 * balance_pgdat() skips over all_unreclaimable after
+		 * DEF_PRIORITY. Effectively, it considers them balanced so
+		 * they must be considered balanced here as well if kswapd
+		 * is to sleep
+		 */
+		if (zone->all_unreclaimable) {
+			balanced += zone->present_pages;
 			continue;
+		}
 
 		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
 								0, 0))
-- 
2.7.4