linux-kernel - Re: [PATCH RFC] sched/fair: let cpu's cfs

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Message-ID: <20160405075112.GC18516@e105550-lin.cambridge.arm.com>
Date:	Tue, 5 Apr 2016 08:51:13 +0100
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	Yuyang Du <yuyang.du@...el.com>
Cc:	Leo Yan <leo.yan@...aro.org>,
	Steve Muckle <steve.muckle@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	linux-kernel@...r.kernel.org, eas-dev@...ts.linaro.org
Subject: Re: [PATCH RFC] sched/fair: let cpu's cfs_rq to reflect task
 migration

On Tue, Apr 05, 2016 at 02:30:03AM +0800, Yuyang Du wrote:
> On Mon, Apr 04, 2016 at 09:48:23AM +0100, Morten Rasmussen wrote:
> > On Sat, Apr 02, 2016 at 03:11:54PM +0800, Leo Yan wrote:
> > > On Fri, Apr 01, 2016 at 03:28:49PM -0700, Steve Muckle wrote:
> > > > I think I follow - Leo please correct me if I mangle your intentions.
> > > > It's an issue that Morten and Dietmar had mentioned to me as well.
> > 
> > Yes. We have been working on this issue for a while without getting to a
> > nice solution yet.
>  
> So do you want a "flat hirarchy" for util_avg - just do util_avg for
> rq and task respectively? Seems it is what you want, and it is even easier?

Pretty much, yes. I can't think of a good reason why we need the
utilization of groups as long as we have the task utilization and the
sum of those for the root cfs_rq.

I'm not saying it can't be implemented, just saying that it will make
utilization tracking for groups redundant and possibly duplicate or hack
some the existing code to implement the new root utilization sum.