linux-kernel - Re: v4.8-rc1: thinkpad x60: running at low frequency even during kernel build

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Date:   Fri, 4 Nov 2016 10:26:36 +0100
From:   Pavel Machek <pavel@....cz>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     rjw@...ysocki.net, linux-pm@...r.kernel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        rui.zhang@...el.com, linux-acpi@...r.kernel.org
Subject: Re: v4.8-rc1: thinkpad x60: running at low frequency even during
 kernel build

Hi!

> I am really confused about where the problem is. 4.8 or 4.9 ? :)

Well, v4.8 runs at too low frequency without explanation, and v4.9
overheats. Both are a problem :-). But it starts to look like v4.9 is
the one where the real problem is.

> On 04-11-16, 09:58, Pavel Machek wrote:
> > On Fri 2016-11-04 09:38:49, Pavel Machek wrote:
> > > Hi!
> > > 
> > > I'm debugging overheats on v4.9-rc1... which did not seem to happen in
> > > v4.8-rc1. I'm running basically "nice make -j 3" on kernel... cpus are
> > > fully loaded. 
> > > 
> > > %Cpu(s):  7.5 us, 18.5 sy, 72.6 ni,  0.0 id,  0.0 wa,  0.0 hi,  1.5
> > > si,  0.0 st
> > > KiB Mem:   3087096 total,  2993076 used,    94020 free,    52900
> > > buffers
> > > KiB Swap:  1681428 total,    60900 used,  1620528 free.  1183664
> > > cached Mem
> > > 
> > > Still, cpus don't stay on maximum frequency on v4.8-rc1. (I suspect
> > > that may be why machine does not overheat).
> > 
> > What is worse, they go to low frequency even with "performance"
> > governor on v4.8-rc1?!
> 
> You sure about it? How did you check it?

See the dumps below. cpuinfo_cur_freq shows 1GHz while compilation is running.

> Also why are you testing on 4.8-rc1? And not a 4.8 stable kernel? What if the
> core is already fixed upstream ?
> 
> There is one core fix in 4.8:
> 
> commit 899bb6642f2a ("cpufreq: skip invalid entries when searching the
> frequency")

Ok, I guess that's not it.

> > 1000000
> > 1000000
> 
> Is this happening because of thermal capping ? That is the only reason that I
> could think of where freq can change with performance governor.

How would I know if it is thermal capping? There's nothing in dmesg.

> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq:1000000
> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver:acpi-cpufreq
> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor:performance
> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq:1000000
> 
> And this value sort of confirms it.
> 
> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq:1000000
> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed:<unsupported>
> > grep: /sys/devices/system/cpu/cpu0/cpufreq/stats: Is a directory
> > pavel@duo:/sys/devices/system/cpu/cpu0/cpufreq$
> > 
> > Let me try v4.9-rc2... that works ok (cpus at the high frequency
> > during the kernel build). Unfortunately that sends my cpus to 99C
> > temperature range (and eventually forces emergency shutdown).
> 
> Unbelievable.
> 
> > v4.9-rc2, current policy changes without me touching it. Notice the
> > 1.47GHz below? I did not do that, it oscilates itself. Is that thermal
> > protection? 
> 
> Looks like to me.
> 
> Can we verify somehow about what's the situation should look like? Perhaps with
> some older stable kernel? And then see if 4.8.X works fine or 4.9-rc.

I can try older kernel from Debian distribution, I guess.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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