From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Steve Muckle <steve.muckle@linaro.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.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>,
Luca Abeni <luca.abeni@unitn.it>
Subject: Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt_capacity
Date: Tue, 15 Dec 2015 13:41:44 +0100 [thread overview]
Message-ID: <20151215124144.GD6357@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKfTPtCRGuWY8aXCKVHumM3nLODsWm55ZHhkBm4v5HzPEn+J_g@mail.gmail.com>
On Tue, Dec 15, 2015 at 05:43:44AM +0100, Vincent Guittot wrote:
> On 14 December 2015 at 17:51, Peter Zijlstra <peterz@infradead.org> wrote:
> > No, since the WCET can and _will_ happen, its the best you can do with
> > cpufreq. If you were to set it lower you could not be able to execute
> > correctly in your 'never' tail cases.
>
> In the context of frequency scaling, This mean that we will never
> reach low frequency
Only if you've stuffed your machine full of deadline tasks, if you take
Luca's example of the I/B frame decoder thingy, then even the WCET for
the I frames should not be very much (albeit significantly more than B
frames).
So while the WCET is pessimistic compared to the avg case, most CPUs can
do video decoding without much effort at all, so even the WCET for the
I-frames might allow us to drop to the lowest cpufreq.
Now, if you were to decode 10 streams at the same time, different story
of course ;-)
next prev parent reply other threads:[~2015-12-15 12:41 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-09 6:19 [RFCv6 PATCH 00/10] sched: scheduler-driven CPU frequency selection Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 01/10] sched: Compute cpu capacity available at current frequency Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 02/10] cpufreq: introduce cpufreq_driver_is_slow Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 03/10] sched: scheduler-driven cpu frequency selection Steve Muckle
2015-12-11 11:04 ` Juri Lelli
2015-12-15 2:02 ` Steve Muckle
2015-12-15 10:31 ` Juri Lelli
2015-12-16 1:22 ` Steve Muckle
2015-12-16 3:48 ` Leo Yan
2015-12-17 1:24 ` Steve Muckle
2015-12-17 7:17 ` Leo Yan
2015-12-18 19:15 ` Steve Muckle
2015-12-19 5:54 ` Leo Yan
2016-01-25 12:06 ` Ricky Liang
2016-01-27 1:14 ` Steve Muckle
2016-02-01 17:10 ` Ricky Liang
2016-02-11 4:44 ` Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 04/10] sched/fair: add triggers for OPP change requests Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 05/10] sched/{core,fair}: trigger OPP change request on fork() Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 06/10] sched/fair: cpufreq_sched triggers for load balancing Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 07/10] sched/fair: jump to max OPP when crossing UP threshold Steve Muckle
2015-12-11 11:12 ` Juri Lelli
2015-12-15 2:42 ` Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 08/10] sched: remove call of sched_avg_update from sched_rt_avg_update Steve Muckle
2015-12-09 6:19 ` [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt_capacity Steve Muckle
2015-12-09 8:50 ` Vincent Guittot
2015-12-10 13:27 ` Luca Abeni
2015-12-10 16:11 ` Vincent Guittot
2015-12-11 7:48 ` Luca Abeni
2015-12-14 14:02 ` Vincent Guittot
2015-12-14 14:38 ` Luca Abeni
2015-12-14 15:17 ` Peter Zijlstra
2015-12-14 15:56 ` Vincent Guittot
2015-12-14 16:07 ` Juri Lelli
2015-12-14 21:19 ` Luca Abeni
2015-12-14 16:51 ` Peter Zijlstra
2015-12-14 21:31 ` Luca Abeni
2015-12-15 12:38 ` Peter Zijlstra
2015-12-15 13:30 ` Luca Abeni
2015-12-15 13:42 ` Peter Zijlstra
2015-12-15 21:24 ` Luca Abeni
2015-12-16 9:28 ` Juri Lelli
2015-12-15 4:43 ` Vincent Guittot
2015-12-15 12:41 ` Peter Zijlstra [this message]
2015-12-15 12:56 ` Vincent Guittot
2015-12-14 21:12 ` Luca Abeni
2015-12-15 4:59 ` Vincent Guittot
2015-12-15 8:50 ` Luca Abeni
2015-12-15 12:20 ` Peter Zijlstra
2015-12-15 12:46 ` Vincent Guittot
2015-12-15 13:18 ` Luca Abeni
2015-12-15 12:23 ` Peter Zijlstra
2015-12-15 13:21 ` Luca Abeni
2015-12-15 12:43 ` Vincent Guittot
2015-12-15 13:39 ` Luca Abeni
2015-12-15 12:58 ` Vincent Guittot
2015-12-15 13:41 ` Luca Abeni
2015-12-09 6:19 ` [RFCv6 PATCH 10/10] sched: rt scheduler sets capacity requirement Steve Muckle
2015-12-11 11:22 ` Juri Lelli
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