linux-kernel - Re: Task group cleanups and optimizations (was: Re: [RFC 00/60] Coscheduling for Linux)

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Message-ID: <20181123165102.GB4855@lerouge>
Date:   Fri, 23 Nov 2018 17:51:03 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Jan H. Schönherr <jschoenh@...zon.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Paul Turner <pjt@...gle.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: Task group cleanups and optimizations (was: Re: [RFC 00/60]
 Coscheduling for Linux)

On Tue, Sep 18, 2018 at 03:22:13PM +0200, Jan H. Schönherr wrote:
> On 09/17/2018 11:48 AM, Peter Zijlstra wrote:
> > Right, so the whole bandwidth thing becomes a pain; the simplest
> > solution is to detect the throttle at task-pick time, dequeue and try
> > again. But that is indeed quite horrible.
> > 
> > I'm not quite sure how this will play out.
> > 
> > Anyway, if we pull off this flattening feat, then you can no longer use
> > the hierarchy for this co-scheduling stuff.
> 
> Yeah. I might be a bit biased towards keeping or at least not fully throwing away
> the nesting of CFS runqueues. ;)

One detail here, is that hierarchical task group a strong requirement for cosched
or could you live with it flattened in the end?