[PATCH 2/2] mm: vmscan: If kswapd has been running too long, allow it to sleep

From: Mel Gorman
Date: Mon May 16 2011 - 11:07:46 EST


Under constant allocation pressure, kswapd can be in the situation where
sleeping_prematurely() will always return true even if kswapd has been
running a long time. Check if kswapd needs to be scheduled.

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
---
mm/vmscan.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index af24d1e..4d24828 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2251,6 +2251,10 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
unsigned long balanced = 0;
bool all_zones_ok = true;

+ /* If kswapd has been running too long, just sleep */
+ if (need_resched())
+ return false;
+
/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
if (remaining)
return true;
--
1.7.3.4

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