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

From: Vincent Guittot <vincent.guittot@linaro.org>
To: Quentin Perret <quentin.perret@arm.com>
Cc: Luca Abeni <luca.abeni@santannapisa.it>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Paul E . McKenney" <paulmck@linux.ibm.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>
Subject: Re: [RFC PATCH 1/6] sched/dl: Improve deadline admission control for asymmetric CPU capacities
Date: Tue, 7 May 2019 15:55:37 +0200	[thread overview]
Message-ID: <CAKfTPtAmekVR59pvBZO-Xp57=qHoxYkvmQwc2fWVa1x4U2_pNg@mail.gmail.com> (raw)
In-Reply-To: <20190507134850.yreebscc3zigfmtd@queper01-lin>

On Tue, 7 May 2019 at 15:48, Quentin Perret <quentin.perret@arm.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