From: Peter Zijlstra <peterz@infradead.org>
To: Juri Lelli <Juri.Lelli@arm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
Rafael Wysocki <rjw@rjwysocki.net>,
Ingo Molnar <mingo@redhat.com>,
linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
Robin Randhawa <robin.randhawa@arm.com>,
Steve Muckle <smuckle.linux@gmail.com>,
tkjos@google.com, Morten Rasmussen <morten.rasmussen@arm.com>
Subject: Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits
Date: Mon, 21 Nov 2016 15:43:43 +0100 [thread overview]
Message-ID: <20161121144343.GH3092@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20161121143727.GO24383@e106622-lin>
On Mon, Nov 21, 2016 at 02:37:27PM +0000, Juri Lelli wrote:
> On 21/11/16 15:17, Peter Zijlstra wrote:
> > Not sure I follow. So by limiting decay to the task value, the moment we
> > add it back to the accumulated signal (wakeup), the accumulated signal
> > jumps up quickly and ramp-up is achieved.
> >
>
> This is true, but it seems that this potentially spiky behaviour
> (which in general depends on tasks composition and periodicity) might
> affect power savings (as in you don't generally want to switch between
> high and low freqs too often). So that's why I was just thinking that
> some sort of smoothing applied to the signal schedutil uses might help.
Hurm.. so during LPC it was said that fast ramp-up was desired. Note
that we'll not ramp down this fast, the accumulated signal will decay
slowly as per blocked-load PELT rules. So only ramp-up is spiky, but
that is what was desired AFAIU.
next prev parent reply other threads:[~2016-11-21 14:43 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-17 5:18 [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits Viresh Kumar
2016-11-21 10:08 ` Viresh Kumar
2016-11-21 10:19 ` Peter Zijlstra
2016-11-21 10:48 ` Viresh Kumar
2016-11-21 11:12 ` Peter Zijlstra
2016-11-21 11:30 ` Viresh Kumar
2016-11-21 11:48 ` Peter Zijlstra
2016-11-21 12:14 ` Juri Lelli
2016-11-21 12:26 ` Peter Zijlstra
2016-11-21 13:53 ` Juri Lelli
2016-11-21 14:17 ` Peter Zijlstra
2016-11-21 14:37 ` Juri Lelli
2016-11-21 14:43 ` Peter Zijlstra [this message]
2016-11-21 14:59 ` Juri Lelli
2016-11-22 9:27 ` Vincent Guittot
2016-11-22 11:03 ` Patrick Bellasi
2016-11-21 14:59 ` Patrick Bellasi
2016-11-21 15:26 ` Peter Zijlstra
2016-11-21 15:34 ` Peter Zijlstra
2016-11-21 16:24 ` Patrick Bellasi
2016-11-21 16:46 ` Peter Zijlstra
2016-11-21 20:53 ` Rafael J. Wysocki
2016-12-29 3:24 ` Wanpeng Li
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