Date: Sat, 5 Jul 2008 21:49:08 +0200
From: =?iso-8859-1?Q?Bj=F6rn?= Steinbrink <B.Steinbrink@gmx.de>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Pavel Machek <pavel@suse.cz>, auke-jan.h.kok@intel.com,
       linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
       len.brown@intel.com, cpufreq@lists.linux.org.uk,
       davej@codemonkey.org.uk
Subject: Re: bug? acpi p-state + ondemand keeps dropping max freq
Message-ID: <20080705194908.GA13149@atjola.homenet>
References: <20080606140846.GA9580@ucw.cz> <20080607213918.GC1746@elf.ucw.cz> <20080607145435.4afc9812@infradead.org> <20080616104159.GA28659@elf.ucw.cz> <20080616074337.46d6f411@infradead.org>
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On 2008.06.16 07:43:37 -0700, Arjan van de Ven wrote:
> On Mon, 16 Jun 2008 12:42:00 +0200
> Pavel Machek <pavel@suse.cz> wrote:
> 
> > On Sat 2008-06-07 14:54:35, Arjan van de Ven wrote:
> > > On Sat, 7 Jun 2008 23:39:18 +0200
> > > Pavel Machek <pavel@suse.cz> wrote:
> > > 
> > > > > # echo 1866000 > scaling_max_freq ; cat scaling_max_freq
> > > > > 800000
> > > > > # echo 1866000 > scaling_max_freq ; cat scaling_max_freq
> > > > > 800000
> > > > > 
> > > > > 
> > > > > This renders my Dothan to utterly poor speeds. (standard T43)
> > > > > 
> > > > > performance cpufreq governor makes no difference - I still can't
> > > > > change the frequency upper/lower values.
> > > > 
> > > > Hmm, I have similar problem in Novell bugzilla, on very different
> > > > hw:
> > > > 
> > > > https://bugzilla.novell.com/show_bug.cgi?id=396311
> > 
> > > are either of you running gnome-power-manager or kpowersaved ?
> > > sometimes these programs (and more likely, the patches added by a
> > > distro maintainer who doesn't fully realize how power works) tend to
> > > muck with kernel settings around CPU frequency that they have
> > > absolutely no business touching...
> > 
> > In novel bugzilla case ignore_ppc=1 helped, so it seems to be BIOS
> > problem, not userland's...
> 
> well as long as the user doesn't use this for production use... the
> BIOS often reduces frequencies available to deal with thermal
> situations, so it's not a good idea to ignore that.

Yep, seems to be a thermal thing. I managed to find some time to play
around with it a bit, and running a cpu hog for a short period of time,
while watching temperature and scaling_max_freq showed this:

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             49 C
cpufreq# cat scaling_max_freq
1866000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             51 C
cpufreq# cat scaling_max_freq
1866000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             52 C
cpufreq# cat scaling_max_freq
1866000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             53 C
cpufreq# cat scaling_max_freq
1866000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             54 C
cpufreq# cat scaling_max_freq
800000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             53 C
cpufreq# cat scaling_max_freq
800000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             51 C
cpufreq# cat scaling_max_freq
800000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             51 C
cpufreq# cat scaling_max_freq
800000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             50 C
cpufreq# cat scaling_max_freq
800000

cpufreq# cat /proc/acpi/thermal_zone/THM0/temperature
temperature:             49 C
cpufreq# cat scaling_max_freq
1866000


So upon reaching 54?C some throttling kicks in and only when going back
to less then 50?C, that limit is lifted again. Too bad that with Linux,
this T43 already runs at about 47?C when idle, so as soon as there's any
load on the cpu, it will scale up for a few seconds and then get
throttled :-(

There's no userspace powersave foo involved here, just the plain
ondemand scaling governor, same happens with the performance governor.

Bj?rn
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