From: Peter Zijlstra <peterz@infradead.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Steve Muckle <steve.muckle@linaro.org>,
Ingo Molnar <mingo@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Juri Lelli <Juri.Lelli@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Michael Turquette <mturquette@baylibre.com>
Subject: Re: [RFCv7 PATCH 01/10] sched: Compute cpu capacity available at current frequency
Date: Tue, 23 Feb 2016 10:19:16 +0100 [thread overview]
Message-ID: <20160223091916.GF6356@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CAJZ5v0hB7KeUPiwie10TeB3cMSPDLVHB5PMgjFn91SCjjC_KjQ@mail.gmail.com>
On Tue, Feb 23, 2016 at 02:41:20AM +0100, Rafael J. Wysocki wrote:
> > /*
> > + * Returns the current capacity of cpu after applying both
> > + * cpu and freq scaling.
> > + */
> > +static unsigned long capacity_curr_of(int cpu)
> > +{
> > + return cpu_rq(cpu)->cpu_capacity_orig *
> > + arch_scale_freq_capacity(NULL, cpu)
>
> What about architectures that don't have this?
They get the 'default' which is a constant SCHED_CAPACITY_SCALE unit.
> Why is that an architecture feature?
Because not all archs can tell the frequency the same way. Some you
program the DVFS state and they really run at this speed, for those you
can simply report back.
For others, x86 for example, you program a DVFS 'hint' and the hardware
does whatever, we'd have to do APERF/MPERF samples to get an idea of the
actual frequency we ran at.
Also, the having of this makes the load tracking slightly more
expensive, instead of compile time constants we get function calls and
actual multiplications. Its not _too_ bad, but still.
> I can easily imagine two x86 platforms using different
> scale_freq_capacity(), for example.
That's up to the arch, if different x86 platforms need different
thingies the arch implementation needs to offer a selector -- this isn't
'hard'.
next prev parent reply other threads:[~2016-02-23 9:19 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 1:22 [RFCv7 PATCH 00/10] sched: scheduler-driven CPU frequency selection Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 01/10] sched: Compute cpu capacity available at current frequency Steve Muckle
2016-02-23 1:41 ` Rafael J. Wysocki
2016-02-23 9:19 ` Peter Zijlstra [this message]
2016-02-26 1:37 ` Rafael J. Wysocki
2016-02-26 9:14 ` Peter Zijlstra
2016-02-23 1:22 ` [RFCv7 PATCH 02/10] cpufreq: introduce cpufreq_driver_is_slow Steve Muckle
2016-02-23 1:31 ` Rafael J. Wysocki
2016-02-26 0:50 ` Michael Turquette
2016-02-26 1:07 ` Steve Muckle
2016-02-26 1:16 ` Rafael J. Wysocki
[not found] ` <20160226185503.2278.20479@quark.deferred.io>
2016-02-26 21:00 ` Rafael J. Wysocki
2016-02-23 1:22 ` [RFCv7 PATCH 03/10] sched: scheduler-driven cpu frequency selection Steve Muckle
2016-02-25 3:55 ` Rafael J. Wysocki
2016-02-25 9:21 ` Peter Zijlstra
2016-02-25 21:04 ` Rafael J. Wysocki
2016-02-25 9:28 ` Peter Zijlstra
2016-02-25 21:08 ` Rafael J. Wysocki
2016-02-26 9:18 ` Peter Zijlstra
2016-02-27 0:08 ` Rafael J. Wysocki
2016-03-01 12:57 ` Peter Zijlstra
2016-03-01 19:44 ` Rafael J. Wysocki
2016-02-25 11:04 ` Rafael J. Wysocki
2016-02-26 0:34 ` Steve Muckle
2016-02-27 2:39 ` Rafael J. Wysocki
2016-02-27 4:17 ` Steve Muckle
2016-02-28 2:26 ` Rafael J. Wysocki
2016-03-01 14:31 ` Peter Zijlstra
2016-03-01 20:32 ` Rafael J. Wysocki
2016-03-01 13:26 ` Peter Zijlstra
2016-03-01 13:17 ` Peter Zijlstra
2016-03-02 7:49 ` Michael Turquette
2016-03-03 2:49 ` Rafael J. Wysocki
2016-03-03 3:50 ` Steve Muckle
2016-03-03 9:34 ` Juri Lelli
2016-03-03 13:03 ` Peter Zijlstra
2016-03-03 14:21 ` Ingo Molnar
2016-02-23 1:22 ` [RFCv7 PATCH 04/10] sched/fair: add triggers for OPP change requests Steve Muckle
2016-03-01 6:51 ` Ricky Liang
2016-03-03 3:55 ` Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 05/10] sched/{core,fair}: trigger OPP change request on fork() Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 06/10] sched/fair: cpufreq_sched triggers for load balancing Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 07/10] sched/fair: jump to max OPP when crossing UP threshold Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 08/10] sched: remove call of sched_avg_update from sched_rt_avg_update Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 09/10] sched/deadline: split rt_avg in 2 distincts metrics Steve Muckle
2016-02-23 1:22 ` [RFCv7 PATCH 10/10] sched: rt scheduler sets capacity requirement Steve Muckle
2016-02-23 1:33 ` [RFCv7 PATCH 00/10] sched: scheduler-driven CPU frequency selection Steve Muckle
2016-03-30 0:45 ` Yuyang Du
2016-03-31 1:35 ` Steve Muckle
2016-03-30 20:22 ` Yuyang Du
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