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Date: Tue, 7 Jul 2015 19:24:18 +0100
From: Morten Rasmussen <morten.rasmussen@....com>
To: peterz@...radead.org, mingo@...hat.com
Cc: vincent.guittot@...aro.org, daniel.lezcano@...aro.org,
Dietmar Eggemann <Dietmar.Eggemann@....com>,
yuyang.du@...el.com, mturquette@...libre.com, rjw@...ysocki.net,
Juri Lelli <Juri.Lelli@....com>, sgurrappadi@...dia.com,
pang.xunlei@....com.cn, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: [RFCv5 PATCH 35/46] 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@...hat.com>
cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
---
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 97eb83e..8e0cbd4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8424,12 +8424,13 @@ 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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