linux-kernel - [PATCH 4/8] Use prepare_to_wait_exclusive() instead prepare_to

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Date:	Mon, 14 Dec 2009 21:30:19 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com, lwoodman@...hat.com,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, minchan.kim@...il.com
Subject: [PATCH 4/8] Use prepare_to_wait_exclusive() instead prepare_to_wait()

if we don't use exclusive queue, wake_up() function wake _all_ waited
task. This is simply cpu wasting.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
 mm/vmscan.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e0cb834..3562a2d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1618,7 +1618,7 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc)
 	 * we would just make things slower.
 	 */
 	for (;;) {
-		prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
+		prepare_to_wait_exclusive(wq, &wait, TASK_UNINTERRUPTIBLE);
 
 		if (atomic_read(&zone->concurrent_reclaimers) <=
 		    max_zone_concurrent_reclaimers)
@@ -1632,7 +1632,7 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc)
                 */
 		if (zone_watermark_ok(zone, sc->order, low_wmark_pages(zone),
 					0, 0)) {
-			wake_up(wq);
+			wake_up_all(wq);
 			finish_wait(wq, &wait);
 			sc->nr_reclaimed += sc->nr_to_reclaim;
 			return -ERESTARTSYS;
-- 
1.6.5.2



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