Re: [RFC 5/6] sched: pack the idle load balance

[Santosh Shilimkar]

On Monday 29 October 2012 06:57 PM, Vincent Guittot wrote:
> On 24 October 2012 17:21, Santosh Shilimkar <santosh.shilimkar@xxxxxx> wrote:
> > On Sunday 07 October 2012 01:13 PM, Vincent Guittot wrote:
> > > Look for an idle CPU close the pack buddy CPU whenever possible.
> >
> > s/close/close to
>
> yes
>
> > > The goal is to prevent the wake up of a CPU which doesn't share the power
> > > line of the pack CPU
> > >
> > > Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> > > ---
> > >    kernel/sched/fair.c |   18 ++++++++++++++++++
> > >    1 file changed, 18 insertions(+)
> > >
> > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > > index 6df53b5..f76acdc 100644
> > > --- a/kernel/sched/fair.c
> > > +++ b/kernel/sched/fair.c
> > > @@ -5158,7 +5158,25 @@ 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;
> >
> > Do you mean SD_SHARE_POWERLINE here ?
>
> No, I just don't want to take hyperthread level for ILB
>
> > > +
> > > +                       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;
> > Can you please expand "idle CPU _close_ the pack buddy CPU" ?
>
> The goal is to packed  the tasks on the pack buddy CPU so when the
> scheduler needs to start ILB, I try to wake up a CPU that is close to
> the buddy and preferably in the same cluster
I see your point now. Thanks for clarification.

Regards
santosh

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