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 <mi...@redhat.com>
cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmus...@arm.com>
---
kernel/sched/fair.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1c248f8..cfe65ae 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8195,6 +8195,8 @@ static void nohz_idle_balance(struct rq *this_rq, enum
cpu_idle_type idle)
clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
}
+static int cpu_overutilized(int cpu, struct sched_domain *sd);
+
/*
* Current heuristic for kicking the idle load balancer in the presence
* of an idle cpu in the system.
@@ -8234,12 +8236,13 @@ static inline bool nohz_kick_needed(struct rq *rq)
if (time_before(now, nohz.next_balance))
return false;
- if (rq->nr_running >= 2)
+ sd = rcu_dereference(rq->sd);
+ if (rq->nr_running >= 2 && (!energy_aware() || cpu_overutilized(cpu,
sd)))
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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