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

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Message-ID: <20150708001914.GE31287@byungchulpark-X58A-UD3R>
Date:	Wed, 8 Jul 2015 09:19:14 +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 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? :)

thank you,
byungchul

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