linux-kernel - Re: [PATCH v7 00/11] track CPU utilization

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Date:   Fri, 6 Jul 2018 11:18:21 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>, mingo@...nel.org,
        linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        juri.lelli@...hat.com, dietmar.eggemann@....com,
        Morten.Rasmussen@....com, valentin.schneider@....com,
        patrick.bellasi@....com, joel@...lfernandes.org,
        daniel.lezcano@...aro.org, quentin.perret@....com,
        luca.abeni@...tannapisa.it, claudio@...dence.eu.com
Subject: Re: [PATCH v7 00/11] track CPU utilization

On Fri, Jul 06, 2018 at 11:35:22AM +0530, Viresh Kumar wrote:
> On 05-07-18, 14:36, Peter Zijlstra wrote:
> > +/*
> > + * This function computes an effective utilization for the given CPU, to be
> > + * used for frequency selection given the linear relation: f = u * f_max.
> > + *
> > + * The scheduler tracks the following metrics:
> > + *
> > + *   cpu_util_{cfs,rt,dl,irq}()
> > + *   cpu_bw_dl()
> > + *
> > + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> > + * synchronized windows and are thus directly comparable.
> > + *
> > + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> > + * which excludes things like IRQ and steal-time. These latter are then accrued in
> > + * the irq utilization.
> > + *
> > + * The DL bandwidth number otoh is not a measured meric but a value computed
> 
>                                                      metric

Indeed, fixed.

> > + * based on the task model parameters and gives the minimal u required to meet
> 
>                                                                u ?

utilization, but for lazy people :-) I'll use the whole word.

> > + * deadlines.
> > + */