From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Quentin Perret <quentin.perret@arm.com>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <Morten.Rasmussen@arm.com>,
viresh kumar <viresh.kumar@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Joel Fernandes <joel@joelfernandes.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH v6 04/11] cpufreq/schedutil: use rt utilization tracking
Date: Fri, 22 Jun 2018 16:11:59 +0200 [thread overview]
Message-ID: <20180622141159.GN2494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKfTPtA+QwUL5c0kqacEYtqONem6_PedMcmq0PAb0RQbi_bRjQ@mail.gmail.com>
On Fri, Jun 22, 2018 at 03:54:24PM +0200, Vincent Guittot wrote:
> On Fri, 22 Jun 2018 at 15:26, Peter Zijlstra <peterz@infradead.org> wrote:
> > $ bc -l
> > define f (u,r,n) { return u + ((u/(1-r)) - u) * (u/(1-r))^n; }
> > f(.2,.7,0)
> > .66666666666666666666
> > f(.2,.7,2)
> > .40740740740740740739
> > f(.2,.7,4)
> > .29218106995884773661
> >
> > So at 10% idle time, we've only inflated what should be 20% to 40%, that
> > is entirely reasonable I think. The linear case gave us 66%. But feel
> > free to increase @n if you feel that helps, 4 is only one mult more than
> > 2 and gets us down to 29%.
>
> I'm a bit lost with your example.
> u = 0.2 (for cfs) and r=0.7 (let say for rt) in your example and idle is 0.1
>
> For rt task, we run 0.7 of the time at f=1 then we will select f=0.4
> for run cfs task with u=0.2 but u is the utilization at f=1 which
> means that it will take 250% of normal time to execute at f=0.4 which
> means 0.5 time instead of 0.2 at f=1 so we are going out of time. In
> order to have enough time to run r and u we must run at least f=0.666
> for cfs = 0.2/(1-0.7).
Argh.. that is n=0. So clearly I went off the rails somewhere.
next prev parent reply other threads:[~2018-06-22 14:12 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-08 12:09 [PATCH v6 00/11] track CPU utilization Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 01/11] sched/pelt: Move pelt related code in a dedicated file Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 02/11] sched/pelt: remove blank line Vincent Guittot
2018-06-21 14:33 ` Peter Zijlstra
2018-06-21 18:42 ` Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 03/11] sched/rt: add rt_rq utilization tracking Vincent Guittot
2018-06-15 11:52 ` Dietmar Eggemann
2018-06-15 12:18 ` Vincent Guittot
2018-06-15 14:55 ` Dietmar Eggemann
2018-06-21 18:50 ` Peter Zijlstra
2018-06-08 12:09 ` [PATCH v6 04/11] cpufreq/schedutil: use rt " Vincent Guittot
2018-06-18 9:00 ` Dietmar Eggemann
2018-06-18 12:58 ` Vincent Guittot
2018-06-21 18:45 ` Peter Zijlstra
2018-06-21 18:57 ` Peter Zijlstra
2018-06-22 8:10 ` Vincent Guittot
2018-06-22 11:41 ` Peter Zijlstra
2018-06-22 12:14 ` Vincent Guittot
2018-06-22 7:58 ` Juri Lelli
2018-06-22 7:58 ` Quentin Perret
2018-06-22 11:37 ` Peter Zijlstra
2018-06-22 11:44 ` Peter Zijlstra
2018-06-22 12:23 ` Vincent Guittot
2018-06-22 13:26 ` Peter Zijlstra
2018-06-22 13:52 ` Peter Zijlstra
2018-06-22 13:54 ` Vincent Guittot
2018-06-22 13:57 ` Vincent Guittot
2018-06-22 14:46 ` Peter Zijlstra
2018-06-22 14:49 ` Vincent Guittot
2018-06-22 14:11 ` Peter Zijlstra [this message]
2018-06-22 14:48 ` Peter Zijlstra
2018-06-22 14:12 ` Vincent Guittot
2018-06-22 12:54 ` Quentin Perret
2018-06-22 13:29 ` Peter Zijlstra
2018-06-22 15:22 ` Peter Zijlstra
2018-06-22 15:30 ` Quentin Perret
2018-06-22 17:24 ` Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 05/11] sched/dl: add dl_rq " Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 06/11] cpufreq/schedutil: use dl " Vincent Guittot
2018-06-08 12:39 ` Juri Lelli
2018-06-08 12:48 ` Vincent Guittot
2018-06-08 12:54 ` Juri Lelli
2018-06-08 13:36 ` Juri Lelli
2018-06-08 13:38 ` Vincent Guittot
2018-06-22 15:24 ` Peter Zijlstra
2018-06-22 17:22 ` Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 07/11] sched/irq: add irq " Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 08/11] cpufreq/schedutil: take into account interrupt Vincent Guittot
2018-06-12 8:54 ` Dietmar Eggemann
2018-06-12 9:10 ` Vincent Guittot
2018-06-12 9:16 ` Vincent Guittot
2018-06-12 9:20 ` Quentin Perret
2018-06-12 9:26 ` Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 09/11] sched: use pelt for scale_rt_capacity() Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 10/11] sched: remove rt_avg code Vincent Guittot
2018-06-08 12:09 ` [PATCH v6 11/11] proc/sched: remove unused sched_time_avg_ms Vincent Guittot
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