linux-kernel - Re: [PATCH v4 14/16] sched/core: uclamp: request CAP_SYS

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Date:   Mon, 24 Sep 2018 18:23:51 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Juri Lelli <juri.lelli@...hat.com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        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>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v4 14/16] sched/core: uclamp: request CAP_SYS_ADMIN by
 default

On 24-Sep 17:56, Peter Zijlstra wrote:
> On Mon, Sep 24, 2018 at 04:14:00PM +0100, Patrick Bellasi wrote:
> > On 21-Sep 11:13, Peter Zijlstra wrote:
> > > Laptops with active cooling however...
> > 
> > How do you see active cooling playing a role ?
> > 
> > Are you thinking, for example, at reduced fan noise if we remain below
> > a certain OPP ?
> > 
> > Are you factoring fans power consumptions into the overall P consumption ?
> 
> Nothing as fancy as that; I just figured that with a larger cooling
> capacity, you can push chips higher onto that curve past the optimal
> IPC/Watt point. Make it go fast etc..

That very concept of "optimal IPC/Watt" point is not something easy to
define considering a monotonic function and without considering the
specific optimization goals.

It really sounds like saying that an LP problem has a unique solution
independently from the optimization function.

Do you think we should "mandate" an optimization function from kernel
space? I'm not saying it does not make sense, but I find it at least a
strong implementation enforcement.

-- 
#include <best/regards.h>

Patrick Bellasi