[PATCH 1/4] sched: do not consider SCHED_IDLE tasks to be cache hot

[Nikhil Rao <ncrao@google.com>]

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@google.com>
---
 kernel/sched.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index dc85ceb..9e01848 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2003,6 +2003,9 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
 	if (p->sched_class != &fair_sched_class)
 		return 0;
 
+	if (unlikely(p->policy == SCHED_IDLE))
+		return 0;
+
 	/*
 	 * Buddy candidates are cache hot:
 	 */
-- 
1.7.1