[RFCv3 PATCH 46/48] sched: Turn off fast idling of cpus on a partially loaded system

[Morten Rasmussen]

From: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>

We do not want to miss out on the ability to do energy-aware idle load
balancing if the system is only partially loaded since the operational
range of energy-aware scheduling corresponds to a partially loaded
system. We might want to pull a single remaining task from a potential
src cpu towards an idle destination cpu if the energy model tells us
this is worth doing to save energy.

cc: Ingo Molnar <mingo@xxxxxxxxxx>
cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b6e2e92..92fd1d8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7734,7 +7734,7 @@ static int idle_balance(struct rq *this_rq)
 	this_rq->idle_stamp = rq_clock(this_rq);
 
 	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
-	    !this_rq->rd->overload) {
+	    (!energy_aware() && !this_rq->rd->overload)) {
 		rcu_read_lock();
 		sd = rcu_dereference_check_sched_domain(this_rq->sd);
 		if (sd)
-- 
1.9.1

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