Message-ID: <521BCD7F.8010501@surriel.com>
Date: Mon, 26 Aug 2013 17:49:51 -0400
From: Rik van Riel <riel@surriel.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>, Ingo Molnar <mingo@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        LKML <linux-kernel@vger.kernel.org>, Mike Galbraith <efault@gmx.de>,
        Alex Shi <alex.shi@intel.com>,
        Preeti U Murthy <preeti@linux.vnet.ibm.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Namhyung Kim <namhyung@kernel.org>, Lei Wen <leiwen@marvell.com>,
        Joonsoo Kim <js1304@gmail.com>
Subject: Re: [PATCH 09/10] sched, fair: Fix the sd_parent_degenerate() code
References: <20130819160058.539049611@infradead.org> <20130819160425.672255367@infradead.org> <CAPM31RLOX9NSaHK9+ysC6yDXvAj2swaoXmg6hHHpMdOJjWBFrQ@mail.gmail.com> <20130826120919.GL31370@twins.programming.kicks-ass.net>
In-Reply-To: <20130826120919.GL31370@twins.programming.kicks-ass.net>
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On 08/26/2013 08:09 AM, Peter Zijlstra wrote:
> On Sat, Aug 24, 2013 at 03:45:57AM -0700, Paul Turner wrote:
>>> @@ -5157,6 +5158,13 @@ cpu_attach_domain(struct sched_domain *s
>>>                         tmp->parent = parent->parent;
>>>                         if (parent->parent)
>>>                                 parent->parent->child = tmp;
>>> +                       /*
>>> +                        * Transfer SD_PREFER_SIBLING down in case of a
>>> +                        * degenerate parent; the spans match for this
>>> +                        * so the property transfers.
>>> +                        */
>>> +                       if (parent->flags & SD_PREFER_SIBLING)
>>> +                               tmp->flags |= SD_PREFER_SIBLING;
>>>                         destroy_sched_domain(parent, cpu);
>>>                 } else
>>>                         tmp = tmp->parent;
>>>
>>
>> Reviewed-by: Paul Turner <pjt@google.com>
> 
> BTW, did that comment make sense to you or would you suggest something
> different? I had/am having a hard time with that comment. Somehow it
> leaves me wanting. I know I understand the issue now, but I'll doubt the
> comment will suffice in a years time :/

The comment made sense to me :)

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