linux-kernel - Re: [PATCH v6 1/2] sched/deadline: Add support for SD_PREFER_SIBLING on find_later

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Date:   Wed, 16 Aug 2017 10:25:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Byungchul Park <byungchul.park@....com>
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, juri.lelli@...il.com,
        kernel-team@....com
Subject: Re: [PATCH v6 1/2] sched/deadline: Add support for
 SD_PREFER_SIBLING on find_later_rq()

On Wed, 16 Aug 2017 23:04:14 +0900
Byungchul Park <byungchul.park@....com> wrote:

> On Wed, Aug 16, 2017 at 09:32:44AM -0400, Steven Rostedt wrote:
> > On Wed, 16 Aug 2017 11:17:36 +0900
> > Byungchul Park <byungchul.park@....com> wrote:
> > 
> >   
> > > Yes, that's what I intended. IOW:
> > > 
> > > If (we found a proper sd, not having SD_PREFER_SIBLING?)
> > > 	use the sd;
> > > else if (we found a proper sd, having SD_PREFER_SIBLING?)
> > > 	use the smallest sd among SD_PREFER_SIBLING sds;  
> > 
> > BTW, what do you mean by "smallest sd"?  
> 
> There might be more than one SD_PREFER_SIBLING domain in its hierachy.
> In that case, we have to choose one of them. Imagine the following
> example, in case that the source cpu is cpu 0:
> 
> [Domain hierachy for cpu 0]
> 
> cpu 0 -+ domain 1                 -+
>        | SD_PREFER_SIBLING flaged  |
> cpu 1 -+                           +- domain 2
>                                    |  SD_PREFER_SIBLING flaged
> cpu 2 -+---------------------------+
>        |
> cpu 3 -+
> 
> In this case, we have to choose domain 1 than 2, because cpus in domain 1
> are closer to the source cpu, cpu 0. That's what I meant.

Then you mean "closest sd", at least that makes more sense in the
context.

-- Steve