linux-kernel - Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits

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Message-ID: <20161121104800.GC10014@vireshk-i7>
Date:   Mon, 21 Nov 2016 16:18:00 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>, Ingo Molnar <mingo@...hat.com>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <Juri.Lelli@....com>,
        Robin Randhawa <robin.randhawa@....com>,
        Steve Muckle <smuckle.linux@...il.com>, tkjos@...gle.com,
        Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [PATCH] cpufreq: schedutil: add up/down frequency transition
 rate limits

On 21-11-16, 11:19, Peter Zijlstra wrote:
> Urgh...
> 
> 
> So no tunables and rate limits here at all please.
> 
> During LPC we discussed the rampup and decay issues and decided that we
> should very much first address them by playing with the PELT stuff.
> Morton was going to play with capping the decay on the util signal. This
> should greatly improve the ramp-up scenario and cure some other wobbles.
> 
> The decay can be set by changing the over-all pelt decay, if so desired.
> 
> Also, there was the idea of; once the above ideas have all been
> explored; tying the freq ram rate to the power curve.
> 
> So NAK on everything tunable here.

Okay, as I told you on IRC, we already have a tunable: rate_limit_us for the
schedutil governor which defines the minimum time before which the governor
wouldn't try to update the frequency again. Perhaps 10-20 ms is the ideal value
for that everyone is using.

So eventually that should also die and we should get inputs from PELT stuff ?

-- 
viresh