linux-kernel - [PATCH -mmotm-2010-01-06-14-34] check high watermark after shrink zone

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Date:	Fri, 8 Jan 2010 14:12:35 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, Rik van Riel <riel@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH -mmotm-2010-01-06-14-34] check high watermark after shrink
 zone

Kswapd check that zone have enough free by zone_water_mark.
If any zone doesn't have enough page, it set all_zones_ok to zero.
all_zone_ok makes kswapd retry not sleeping.

I think the watermark check before shrink zone is pointless.
Kswapd try to shrink zone then the check is meaningul.

This patch move the check after shrink zone.
Signed-off-by: Minchan Kim <minchan.kim@...il.com>
CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC: Mel Gorman <mel@....ul.ie>
CC: Rik van Riel <riel@...hat.com>
---
 mm/vmscan.c |   21 +++++++++++----------
 1 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 885207a..b81adf8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2057,9 +2057,6 @@ loop_again:
 					priority != DEF_PRIORITY)
 				continue;
 
-			if (!zone_watermark_ok(zone, order,
-					high_wmark_pages(zone), end_zone, 0))
-				all_zones_ok = 0;
 			temp_priority[i] = priority;
 			sc.nr_scanned = 0;
 			note_zone_scanning_priority(zone, priority);
@@ -2099,13 +2096,17 @@ loop_again:
 			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
 				sc.may_writepage = 1;
 
-			/*
-			 * We are still under min water mark. it mean we have
-			 * GFP_ATOMIC allocation failure risk. Hurry up!
-			 */
-			if (!zone_watermark_ok(zone, order, min_wmark_pages(zone),
-					      end_zone, 0))
-				has_under_min_watermark_zone = 1;
+			if (!zone_watermark_ok(zone, order,
+					high_wmark_pages(zone), end_zone, 0)) {
+				all_zones_ok = 0;
+				/*
+				 * We are still under min water mark. it mean we have
+				 * GFP_ATOMIC allocation failure risk. Hurry up!
+				 */
+				if (!zone_watermark_ok(zone, order, min_wmark_pages(zone),
+						      end_zone, 0))
+					has_under_min_watermark_zone = 1;
+			}
 
 		}
 		if (all_zones_ok)
-- 
1.5.6.3



-- 
Kind regards,
Minchan Kim
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