linux-kernel - Re: [PATCH v2 08/12] sched/core: uclamp: extend cpu's cgroup controller

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Date:   Thu, 26 Jul 2018 17:39:19 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Patrick Bellasi <patrick.bellasi@....com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.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 v2 08/12] sched/core: uclamp: extend cpu's cgroup
 controller

On Tue, Jul 24, 2018 at 06:29:02AM -0700, Tejun Heo wrote:
> Hello, Patrick.
> 
> On Mon, Jul 23, 2018 at 06:22:15PM +0100, Patrick Bellasi wrote:
> > However, the "best effort" bandwidth control we have for CFS and RT
> > can be further improved if, instead of just looking at time spent on
> > CPUs, we provide some more hints to the scheduler to know at which
> > min/max "MIPS" we want to consume the (best effort) time we have been
> > allocated on a CPU.
> > 
> > Such a simple extension is still quite useful to satisfy many use-case
> > we have, mainly on mobile systems, like the ones I've described in the
> >    "Newcomer's Short Abstract (Updated)"
> > section of the cover letter:
> >    https://lore.kernel.org/lkml/20180716082906.6061-1-patrick.bellasi@arm.com/T/#u
> 
> So, that's all completely fine but then let's please not give it a
> name which doesn't quite match what it does.  We can just call it
> e.g. cpufreq range control.

But then what name can one give it if it does more than one thing, like
task-placement and CPU frequency control?

It doesn't make sense to name it cpufreq IMHO. Its a clamp on the utilization
of the task which can be used for many purposes.

thanks,

- Joel