linux-kernel - Re: [RFC PATCH 2/6] sched/dl: Capacity-aware migrations

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Date:   Tue, 7 May 2019 16:41:27 +0200
From:   luca abeni <luca.abeni@...tannapisa.it>
To:     Quentin Perret <quentin.perret@....com>
Cc:     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>,
        Vincent Guittot <vincent.guittot@...aro.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 2/6] sched/dl: Capacity-aware migrations

Hi,

On Tue, 7 May 2019 15:10:50 +0100
Quentin Perret <quentin.perret@....com> wrote:

> On Monday 06 May 2019 at 06:48:32 (+0200), Luca Abeni wrote:
> >  static inline unsigned long cpu_bw_dl(struct rq *rq)
> >  {
> > -	return (rq->dl.running_bw * SCHED_CAPACITY_SCALE) >>
> > BW_SHIFT;
> > +	unsigned long res;
> > +
> > +	res = (rq->dl.running_bw * SCHED_CAPACITY_SCALE) >>
> > BW_SHIFT; +
> > +	return (res << SCHED_CAPACITY_SHIFT) /
> > +	       arch_scale_cpu_capacity(NULL, rq->cpu);  
> 
> The only user of cpu_bw_dl() is schedutil right ? If yes, we probably
> don't want to scale things here -- schedutil already does this I
> believe.

I think I added this modification because I arrived to the conclusion
that schedutils does not perform this rescaling (at least, I think it
did not perform it when I wrote the patch :)


BTW, while re-reading the patch I do not understand why this change was
added in this specific patch... I suspect it should have gone in a
separate patch.



				Luca

> 
> Thanks,
> Quentin
> 
> >  }
> >  
> >  static inline unsigned long cpu_util_dl(struct rq *rq)
> > -- 
> > 2.20.1
> >