[RFCv4 PATCH 34/34] sched: Disable energy-unfriendly nohz kicks

[Morten Rasmussen]

With energy-aware scheduling enabled nohz_kick_needed() generates many
nohz idle-balance kicks which lead to nothing when multiple tasks get
packed on a single cpu to save energy. This causes unnecessary wake-ups
and hence wastes energy. Make these conditions depend on !energy_aware()
for now until the energy-aware nohz story gets sorted out.

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

Signed-off-by: Morten Rasmussen <morten.rasmussen@xxxxxxx>
---
 kernel/sched/fair.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8efeb1d..e6d32e6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8382,12 +8382,13 @@ static inline bool nohz_kick_needed(struct rq *rq)
 	if (time_before(now, nohz.next_balance))
 		return false;
 
-	if (rq->nr_running >= 2)
+	if (rq->nr_running >= 2 &&
+	    (!energy_aware() || cpu_overutilized(cpu)))
 		return true;
 
 	rcu_read_lock();
 	sd = rcu_dereference(per_cpu(sd_busy, cpu));
-	if (sd) {
+	if (sd && !energy_aware()) {
 		sgc = sd->groups->sgc;
 		nr_busy = atomic_read(&sgc->nr_busy_cpus);
 
-- 
1.9.1

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