Messages in this thread | | | Date | Fri, 26 Apr 2013 15:47:33 +0200 | Subject | Re: [PATCH 04/14] sched: pack the idle load balance | From | Vincent Guittot <> |
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On 26 April 2013 14:49, Peter Zijlstra <peterz@infradead.org> wrote: > On Thu, Apr 25, 2013 at 07:23:20PM +0200, Vincent Guittot wrote: >> Look for an idle CPU close to the pack buddy CPU whenever possible. >> The goal is to prevent the wake up of a CPU which doesn't share the power >> domain of the pack buddy CPU. >> >> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> >> Reviewed-by: Morten Rasmussen <morten.rasmussen@arm.com> >> --- >> kernel/sched/fair.c | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 6adc57c..a985c98 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -5469,7 +5469,26 @@ static struct { >> >> static inline int find_new_ilb(int call_cpu) >> { >> + struct sched_domain *sd; >> int ilb = cpumask_first(nohz.idle_cpus_mask); >> + int buddy = per_cpu(sd_pack_buddy, call_cpu); >> + >> + /* >> + * If we have a pack buddy CPU, we try to run load balance on a CPU >> + * that is close to the buddy. >> + */ >> + if (buddy != -1) { >> + for_each_domain(buddy, sd) { >> + if (sd->flags & SD_SHARE_CPUPOWER) >> + continue; >> + >> + ilb = cpumask_first_and(sched_domain_span(sd), >> + nohz.idle_cpus_mask); >> + >> + if (ilb < nr_cpu_ids) >> + break; >> + } >> + } >> >> if (ilb < nr_cpu_ids && idle_cpu(ilb)) >> return ilb; > > Ha! and here you hope people won't put multiple big-little clusters in a single > machine? :-)
yes, we will probably face this situation sooner or later but the other little clusters will probably be not less close than the local big cluster from a power domain point of view. That's why i look for the small sched_domain level to the largest one
> > >
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