From: Juri Lelli <juri.lelli@redhat.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>,
luca abeni <luca.abeni@santannapisa.it>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Wei Wang <wvw@google.com>, Quentin Perret <qperret@google.com>,
Alessio Balsini <balsini@google.com>,
Pavan Kondeti <pkondeti@codeaurora.org>,
Patrick Bellasi <patrick.bellasi@matbug.net>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Qais Yousef <qais.yousef@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities
Date: Fri, 17 Apr 2020 17:08:28 +0200 [thread overview]
Message-ID: <20200417150828.GS9767@localhost.localdomain> (raw)
In-Reply-To: <8734b37e-5602-79dc-c7a8-c41fd9eb86b5@arm.com>
On 17/04/20 16:55, Dietmar Eggemann wrote:
> On 17.04.20 14:19, Juri Lelli wrote:
> > On 09/04/20 19:29, Dietmar Eggemann wrote:
>
> [...]
>
> >> Maybe we can do a hybrid. We have rd->span and rd->sum_cpu_capacity and
> >> with the help of an extra per-cpu cpumask we could just
> >
> > Hummm, I like the idea, but
> >
> >> DEFINE_PER_CPU(cpumask_var_t, dl_bw_mask);
> >>
> >> dl_bw_cpus(int i) {
> >
> > This works if calls are always local to the rd we are interested into
> > (argument 'i' isn't used). Are we always doing that?
>
> I thought so. The existing dl_bw_cpus(int i) implementation already
> assumes this by using:
>
> struct root_domain *rd = cpu_rq(i)->rd;
Hummm, can't dl_task_can_attach() call it with a dest_cpu different from
this_cpu?
Current implementation uses 'i' argument to get to the right root_domain
(e.g., when moving tasks between execlusive set).
> ...
>
> for_each_cpu_and(i, rd->span, cpu_active_mask)
>
> Or did you refer to something else here?
>
> And the patch would not introduce new places in which we call
> dl_bw_cpus(). It will just replace some with a dl_bw_capacity() call.
>
> >> struct cpumask *cpus = this_cpu_cpumask_var_ptr(dl_bw_mask);
> >> ...
> >> cpumask_and(cpus, rd->span, cpu_active_mask);
> >>
> >> return cpumask_weight(cpus);
> >> }
> >>
> >> and
> >>
> >> dl_bw_capacity(int i) {
> >>
> >> struct cpumask *cpus = this_cpu_cpumask_var_ptr(dl_bw_mask);
> >> ...
> >> cpumask_and(cpus, rd->span, cpu_active_mask);
> >> if (cpumask_equal(cpus, rd->span))
> >> return rd->sum_cpu_capacity;
> >
> > What if capacities change between invocations (with the same span)?
> > Can that happen?
>
> The CPU capacity should only change during initial bring-up. On
> asymmetric CPU capacity systems we have to re-create the Sched Domain
> (SD) topology after CPUfreq becomes available.
>
> After the initial build and this first rebuild of the SD topology, the
> CPU capacity should be stable.
>
> Everything which might follow afterwards (starting EAS, exclusive
> cpusets or CPU hp) will not change the CPU capacity.
>
> Obviously, if you defer loading CPUfreq driver after you started DL
> scheduling you can break things. But this is not considered a valid
> environment here.
OK. Makes sense.
next prev parent reply other threads:[~2020-04-17 15:08 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-08 9:50 [PATCH 0/4] Capacity awareness for SCHED_DEADLINE Dietmar Eggemann
2020-04-08 9:50 ` [PATCH 1/4] sched/topology: Store root domain CPU capacity sum Dietmar Eggemann
2020-04-08 12:29 ` Vincent Guittot
2020-04-08 16:30 ` Dietmar Eggemann
2020-04-08 17:03 ` Vincent Guittot
2020-04-09 13:50 ` Dietmar Eggemann
2020-04-09 14:13 ` Vincent Guittot
2020-04-14 9:20 ` Dietmar Eggemann
2020-04-14 12:45 ` Quentin Perret
2020-04-14 15:27 ` Dietmar Eggemann
2020-04-14 15:43 ` Vincent Guittot
2020-04-08 9:50 ` [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities Dietmar Eggemann
2020-04-08 10:42 ` Valentin Schneider
2020-04-08 12:26 ` Dietmar Eggemann
2020-04-08 13:30 ` luca abeni
2020-04-08 14:23 ` Qais Yousef
2020-04-08 15:01 ` Valentin Schneider
2020-04-09 17:29 ` Dietmar Eggemann
2020-04-14 11:40 ` Qais Yousef
2020-04-14 14:29 ` Valentin Schneider
2020-04-14 15:41 ` Qais Yousef
2020-04-14 14:28 ` Valentin Schneider
2020-04-17 12:19 ` Juri Lelli
2020-04-17 14:55 ` Dietmar Eggemann
2020-04-17 15:08 ` Juri Lelli [this message]
2020-04-17 15:47 ` Juri Lelli
2020-04-08 9:50 ` [PATCH 3/4] sched/deadline: Make DL capacity-aware Dietmar Eggemann
2020-04-10 12:52 ` Juri Lelli
2020-04-15 9:39 ` Dietmar Eggemann
2020-04-15 13:20 ` Juri Lelli
2020-04-15 16:42 ` luca abeni
2020-04-16 13:19 ` Juri Lelli
2020-04-08 9:50 ` [PATCH 4/4] sched/deadline: Implement fallback mechanism for !fit case Dietmar Eggemann
2020-04-09 10:25 ` Qais Yousef
2020-04-09 13:00 ` luca abeni
2020-04-09 14:55 ` Qais Yousef
2020-04-09 18:43 ` Dietmar Eggemann
2020-04-14 11:29 ` Qais Yousef
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