[PATCH] mm: yield during swap prefetching

[Con Kolivas <kernel@kolivas.org>]

Swap prefetching doesn't use very much cpu but spends a lot of time waiting on 
disk in uninterruptible sleep. This means it won't get preempted often even at 
a low nice level since it is seen as sleeping most of the time. We want to 
minimise its cpu impact so yield where possible.

Signed-off-by: Con Kolivas <kernel@kolivas.org>
---
 mm/swap_prefetch.c |    1 +
 1 file changed, 1 insertion(+)

Index: linux-2.6.15-ck5/mm/swap_prefetch.c
===================================================================
--- linux-2.6.15-ck5.orig/mm/swap_prefetch.c	2006-03-02 14:00:46.000000000 +1100
+++ linux-2.6.15-ck5/mm/swap_prefetch.c	2006-03-08 08:49:32.000000000 +1100
@@ -421,6 +421,7 @@ static enum trickle_return trickle_swap(
 
 		if (trickle_swap_cache_async(swp_entry, node) == TRICKLE_DELAY)
 			break;
+		yield();
 	}
 
 	if (sp_stat.prefetched_pages) {