linux-kernel - Re: [PATCH v7 1/2] sched/deadline: Add support for SD_PREFER_SIBLING on find_later

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Date:   Fri, 18 Aug 2017 16:55:33 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     "Joel Fernandes (Google)" <joel.opensrc@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        juri.lelli@...il.com, rostedt@...dmis.org, kernel-team@....com,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v7 1/2] sched/deadline: Add support for SD_PREFER_SIBLING
 on find_later_rq()

On Fri, Aug 18, 2017 at 12:21:46AM -0700, Joel Fernandes (Google) wrote:
> Hi Byungchul,
> 
> On Thu, Aug 17, 2017 at 11:05 PM, Byungchul Park <byungchul.park@....com> wrote:
> > It would be better to avoid pushing tasks to other cpu within
> > a SD_PREFER_SIBLING domain, instead, get more chances to check other
> > siblings.
> >
> > Signed-off-by: Byungchul Park <byungchul.park@....com>
> > ---
> >  kernel/sched/deadline.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 52 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> > index 0223694..8f69a37 100644
> > --- a/kernel/sched/deadline.c
> > +++ b/kernel/sched/deadline.c
> > @@ -1319,12 +1319,35 @@ static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu
> >
> >  static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
> >
> > +/*
> > + * Find the first cpu in: mask & sd & ~prefer
> > + */
> > +static int find_cpu(const struct cpumask *mask,
> > +                   const struct sched_domain *sd,
> > +                   const struct sched_domain *prefer)
> > +{
> > +       const struct cpumask *sds = sched_domain_span(sd);
> > +       const struct cpumask *ps  = prefer ? sched_domain_span(prefer) : NULL;
> > +       int cpu = -1;
> > +
> > +       while ((cpu = cpumask_next(cpu, mask)) < nr_cpu_ids) {
> 
> This can be simplified to for_each_cpu(cpu, mask) ?

Indeed, exactly.

I will use that, thank you.