From 0b625debbaa29bf992fe9d181127e114244eebac Mon Sep 17 00:00:00 2001 From: Morten Rasmussen Date: Tue, 3 Feb 2015 13:54:11 +0000 Subject: 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 cc: Peter Zijlstra Signed-off-by: Morten Rasmussen --- 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 3a8a8acc3b8..9823e39f164 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7735,6 +7735,8 @@ end: 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. @@ -7774,12 +7776,13 @@ 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); -- cgit v1.2.3