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Subject[PATCH 4/8] Use prepare_to_wait_exclusive() instead prepare_to_wait()
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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@jp.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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