linux-kernel - Re: [PATCH] sched: let __sched_period() use rq cfs's nr

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Message-ID: <20150709045431.GG31287@byungchulpark-X58A-UD3R>
Date:	Thu, 9 Jul 2015 13:54:32 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: let __sched_period() use rq cfs's nr_running

On Wed, Jul 08, 2015 at 09:19:14AM +0900, Byungchul Park wrote:
> On Tue, Jul 07, 2015 at 01:28:18PM -0700, Cong Wang wrote:
> > On Mon, Jul 6, 2015 at 9:40 PM,  <byungchul.park@....com> wrote:
> > > From: Byungchul Park <byungchul.park@....com>
> > >
> > > __sched_period() returns a period which a rq can have. the period has to be
> > > stretched by the number of task *the rq has*, when nr_running > nr_latency.
> > > otherwise, task slice can be very smaller than sysctl_sched_min_granularity
> > > depending on the position of tg hierarchy when CONFIG_FAIR_GROUP_SCHED.
> > 
> > 
> > Hmm, rq_of(cfs_rq)->cfs should point to the root cfs_rq whose
> > ->nr_running is number of running entities at root level? This
> > doesn't look right.
> 
> hello, cong wang,
> 
> __sched_period() returns a root level period now. stretching the period with
> a local task group's nr_running is meaningless for getting this period.
> is there something i missed? :)

i am very sorry for my wrong patch, with which i cannot achieve what i intend.

what i intended is to use rq_of(cfs_rq)'s nr_number, not rq_of(cfs_rq)->cfs's,
so that __sched_period() returns a period which a rq can have. i need resend 
patch :( but i wonder what do you think about my basic concern?

thank you,
byungchul

> 
> thank you,
> byungchul
> 
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