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    SubjectRe: [PATCH 04/14] sched: pack the idle load balance
    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? :-)





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