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Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq()

From Byungchul Park <byungchul.park@lge.com>
Newsgroups linux.kernel
Subject Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq()
Date 2017-08-25 03:40 +0200
Message-ID <uibLk-5Xx-15@gated-at.bofh.it> (permalink)
References <uhOOK-81q-3@gated-at.bofh.it> <uhOOK-81q-5@gated-at.bofh.it> <ui0PU-7jh-15@gated-at.bofh.it>
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On Thu, Aug 24, 2017 at 09:55:14AM -0400, Steven Rostedt wrote:
> On Thu, 24 Aug 2017 10:06:03 +0900
> Byungchul Park <byungchul.park@lge.com> wrote:
> 
> > Hello Steven,
> > 
> > Can I keep your reviewed-by with comments modified?
> 
> Yes, but I have one nit.
> 
> 
> > @@ -1668,9 +1691,35 @@ static int find_lowest_rq(struct task_struct *task)
> >  				return this_cpu;
> >  			}
> >  
> > -			best_cpu = cpumask_first_and(lowest_mask,
> > -						     sched_domain_span(sd));
> > +			/*
> > +			 * If a cpu being in lowest_mask & current sd &
> > +			 * ~prefer sd is valid, that becomes our choice.
> 
> I can't parse the above sentence.

I might have simplified the comment too much.

~prefer means we want to exclude the domain span having SD_PREFER_SIBLING,
since they should be considered as fallback candidates.

W/o ~prefer, a cpu in the domain might be chosen when we consider higher
domain than the domain having SD_PREFER_SIBLING, as the best cpu, not
fallback.

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Thread

[PATCH v10 0/2] Make find_later_rq() choose a closer cpu in topology Byungchul Park <byungchul.park@lge.com> - 2017-08-24 03:10 +0200
  [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq() Byungchul Park <byungchul.park@lge.com> - 2017-08-24 03:10 +0200
    Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on  find_lowest_rq() Steven Rostedt <rostedt@goodmis.org> - 2017-08-24 16:00 +0200
      Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on  find_lowest_rq() Byungchul Park <byungchul.park@lge.com> - 2017-08-25 03:40 +0200
        Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on  find_lowest_rq() Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 03:50 +0200
          Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on  find_lowest_rq() Byungchul Park <byungchul.park@lge.com> - 2017-08-25 04:10 +0200
  [PATCH v10 1/2] sched/deadline: Add support for SD_PREFER_SIBLING on find_later_rq() Byungchul Park <byungchul.park@lge.com> - 2017-08-24 03:10 +0200

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