[PATCH] [93/275] sched: Do not consider SCHED_IDLE tasks to be cache hot

[Andi Kleen]

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
Commit: ef8002f6848236de5adc613063ebeabddea8a6fb upstream

This patch adds a check in task_hot to return if the task has SCHED_IDLE
policy. SCHED_IDLE tasks have very low weight, and when run with regular
workloads, are typically scheduled many milliseconds apart. There is no
need to consider these tasks hot for load balancing.

Signed-off-by: Nikhil Rao <ncrao@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
LKML-Reference: <1287173550-30365-2-git-send-email-ncrao@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Mike Galbraith <efault@xxxxxx>
Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 kernel/sched.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6.35.y/kernel/sched.c
===================================================================
--- linux-2.6.35.y.orig/kernel/sched.c	2011-03-29 23:02:59.968300981 -0700
+++ linux-2.6.35.y/kernel/sched.c	2011-03-29 23:55:02.689398361 -0700
@@ -1972,6 +1972,9 @@
 	if (p->sched_class != &fair_sched_class)
 		return 0;
 
+	if (unlikely(p->policy == SCHED_IDLE))
+		return 0;
+
 	/*
 	 * Buddy candidates are cache hot:
 	 */
--
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