linux-kernel - Re: [RFC] cpufreq: governor: Set MIN_LATENCY

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Message-ID: <CAKohpomt+7YtD5s+XJ5-boCu_atCB0kHhuifWOGVwy7DqnBLPA@mail.gmail.com>
Date:	Tue, 26 Feb 2013 16:20:07 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Thomas Renninger <trenn@...e.de>
Cc:	rjw@...k.pl, cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	robin.randhawa@....com, Steve.Bannister@....com,
	Liviu.Dudau@....com, charles.garcia-tobin@....com
Subject: Re: [RFC] cpufreq: governor: Set MIN_LATENCY_MULTIPLIER to 20

On 26 February 2013 16:14, Thomas Renninger <trenn@...e.de> wrote:
> Redefining MIN_LATENCY_MULTIPLIER shouldn't hurt that much, but this looks
> like a workaround.
> It only modifies the minimal sampling rate that userspace can set.

Yes.

> You would still need to set something from userspace to get the perfect
> sampling rate for this platform.

Yes. We still need to fix sampling rate from userspace.

> I wonder where the cpufreq driver does get the 1ms latency from?
> Is this value valid?
> The driver should return the correct latency, then there is no need for
> workarounds like this.

I am talking about ARM Vexpress TC2 (Test Chip) big LITTLE SoC here. Its
not a production type SoC and freq change is a bit slow here. Its really around
1 ms :)

But the real systems may not have this big of latency.

Anyway, how do you come to 100 value in your initial patch. What motivated you
to fix it there?

--
viresh
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