linux-kernel - Re: [PATCH v3 06/14] sched/cpufreq: uclamp: add utilization clamping for RT tasks

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Message-ID: <20180813101724.GB2605@e110439-lin>
Date:   Mon, 13 Aug 2018 11:17:24 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Quentin Perret <quentin.perret@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v3 06/14] sched/cpufreq: uclamp: add utilization clamping
 for RT tasks

Hi Quentin!

On 09-Aug 16:55, Quentin Perret wrote:
> Hi Patrick,
> 
> On Thursday 09 Aug 2018 at 16:41:56 (+0100), Patrick Bellasi wrote:
> > > IIUC, not far below this you should still have something like:
> > > 
> > > 	if (rt_rq_is_runnable(&rq->rt))
> > > 		return max;
> > 
> > Do you mean that when RT tasks are RUNNABLE we still want to got to
> > MAX? Not sure to understand... since this patch is actually to clamp
> > the RT class...
> 
> Argh, reading my message again it wasn't very clear indeed. Sorry about
> that ...
> 
> What I'm try to say is that your patch does _not_ remove the snippet of code
> above from sugov_get_util(). So I think that when a RT task is runnable,
> you will not reach the end of the function where the clamping is done.
> And this is not what you want AFAICT.
> 
> Does that make any sense ?

Oh gotcha... you right, I've missed that bit when I rebased on tip.
Will fix on the next iteration!

-- 
#include <best/regards.h>

Patrick Bellasi