linux-kernel - Re: [patch v8 3/9] sched: set initial value of runnable avg for new forked task

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Message-ID: <20130617092146.GM3204@twins.programming.kicks-ass.net>
Date:	Mon, 17 Jun 2013 11:21:46 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alex Shi <alex.shi@...el.com>
Cc:	Paul Turner <pjt@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Michael Wang <wangyun@...ux.vnet.ibm.com>,
	Jason Low <jason.low2@...com>,
	Changlong Xie <changlongx.xie@...el.com>, sgruszka@...hat.com,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [patch v8 3/9] sched: set initial value of runnable avg for new
 forked task

On Fri, Jun 14, 2013 at 10:16:28PM +0800, Alex Shi wrote:
> On 06/14/2013 07:09 PM, Paul Turner wrote:
> > Minor comments; looks good otherwise.
> > 
> > Signed-off-by: Paul Turner <pjt@...gle.com>
> 
> thanks a lot Paul. the patch with your input updated here:
> 
> BTW, would you like to give some comments on the last patch of this patchset?
> 
> ---
> From ed35080d0bae803d68f84a3e683d34a356a5a5de Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@...el.com>
> Date: Tue, 14 May 2013 09:41:09 +0800
> Subject: [PATCH 3/8] sched: set initial value of runnable avg for new forked
>  task
> 
> We need initialize the se.avg.{decay_count, load_avg_contrib} for a
> new forked task.
> Otherwise random values of above variables cause mess when do new task
> enqueue:
>     enqueue_task_fair
>         enqueue_entity
>             enqueue_entity_load_avg
> 
> and make forking balancing imbalance since incorrect load_avg_contrib.
> 
> Further more, Morten Rasmussen notice some tasks were not launched at
> once after created. So Paul and Peter suggest giving a start value for
> new task runnable avg time same as sched_slice().
> 
> Signed-off-by: Alex Shi <alex.shi@...el.com>
> Signed-off-by: Paul Turner <pjt@...gle.com>

Should you all go read: Documentation/SubmittingPatches , or am I
somehow confused on the SoB rules?
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