linux-kernel - Re: [patch v4 08/18] Revert "sched: Introduce temporary FAIR_GROUP

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Message-ID: <CAPM31RLi+e=2kmwxDOewe=+LHrHGiVTuo-+3WeAFEmsWmi1fnw@mail.gmail.com>
Date:	Wed, 13 Feb 2013 07:45:54 -0800
From:	Paul Turner <pjt@...gle.com>
To:	Alex Shi <alex.shi@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	torvalds@...ux-foundation.org, mingo@...hat.com,
	tglx@...utronix.de, akpm@...ux-foundation.org,
	arjan@...ux.intel.com, bp@...en8.de, namhyung@...nel.org,
	efault@....de, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v4 08/18] Revert "sched: Introduce temporary
 FAIR_GROUP_SCHED dependency for load-tracking"

On Wed, Feb 13, 2013 at 7:23 AM, Alex Shi <alex.shi@...el.com> wrote:
> On 02/12/2013 06:27 PM, Peter Zijlstra wrote:
>> On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote:
>>> Remove CONFIG_FAIR_GROUP_SCHED that covers the runnable info, then
>>> we can use runnable load variables.
>>>
>> It would be nice if we could quantify the performance hit of doing so.
>> Haven't yet looked at later patches to see if we remove anything to
>> off-set this.
>>
>
> In our rough testing, no much clear performance changes.
>

I'd personally like this to go with a series that actually does
something with it.

There's been a few proposals floating around on _how_ to do this; but
the challenge is in getting it stable enough that all of the wake-up
balancing does not totally perforate your stability gains into the
noise.  select_idle_sibling really is your nemesis here.

It's a small enough patch that it can go at the head of any such
series (and indeed; it was originally structured to make such a patch
rather explicit.)

> --
> Thanks
>     Alex
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