sched: Disable energy-unfriendly nohz kicks

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@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ae4f1ee9cf0c17c43091887d1860263723583c63..7327221c991ecbc7d710faddcb8cc2cc1cbde287 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8259,12 +8259,13 @@ 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);