linux-kernel - Re: [RFC PATCH 1/6] sched/dl: Improve deadline admission control for asymmetric CPU capacities

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Message-ID: <CAKfTPtAmekVR59pvBZO-Xp57=qHoxYkvmQwc2fWVa1x4U2_pNg@mail.gmail.com>
Date:   Tue, 7 May 2019 15:55:37 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     Luca Abeni <luca.abeni@...tannapisa.it>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>
Subject: Re: [RFC PATCH 1/6] sched/dl: Improve deadline admission control for
 asymmetric CPU capacities

On Tue, 7 May 2019 at 15:48, Quentin Perret <quentin.perret@....com> wrote:
>
> Hi Luca,
>
> On Monday 06 May 2019 at 06:48:31 (+0200), Luca Abeni wrote:
> > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> > index edfcf8d982e4..646d6d349d53 100644
> > --- a/drivers/base/arch_topology.c
> > +++ b/drivers/base/arch_topology.c
> > @@ -36,6 +36,7 @@ DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
> >
> >  void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
> >  {
> > +     topology_update_cpu_capacity(cpu, per_cpu(cpu_scale, cpu), capacity);
>
> Why is that one needed ? Don't you end up re-building the sched domains
> after this anyways ?

I was looking at the same point.
Also this doesn't take into account if the cpu is offline

Do we also need of the line below in set_rq_online
+               rq->rd->rd_capacity += arch_scale_cpu_capacity(NULL,
cpu_of(rq));

building the sched_domain seems a better place to set rq->rd->rd_capacity

>
> >       per_cpu(cpu_scale, cpu) = capacity;
> >  }
>
> Thanks,
> Quentin