Who's playing with scaling_max_freq?

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Who's playing with scaling_max_freq?

Stefan Monnier
Max scaling_max_freq seems stuck at 1GHz even though it should be able
to go up to 1.83GHz.

    # echo 1833000 >/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq; cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
    1000000
    # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
    1833000 1333000 1000000
    #

This is on a Thinkpad T60 running Debian stable.  Any idea what might be
causing this?  Or at least, which part of the system might cause
scaling_max_freq to be (re)set to 1GHz right after I force-set it to 1.83GHz?
Would it be some daemon like systemd or rather the kernel?

This Thinkpad T60 is actually used as a desktop: it's parked in a dock
(with the lid is closed) where I have it connected to a keyboard and monitor.
Opening the lid doesn't seem to make any difference, tho.


        Stefan

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Re: Who's playing with scaling_max_freq?

Henrique de Moraes Holschuh-2
On Tue, Apr 26, 2016, at 22:23, Stefan Monnier wrote:

> Max scaling_max_freq seems stuck at 1GHz even though it should be able
> to go up to 1.83GHz.
>
>     # echo 1833000
>     >/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq; cat
>     /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
>     1000000
>     # cat
>     /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
>     1833000 1333000 1000000
>     #
>
> This is on a Thinkpad T60 running Debian stable.  Any idea what might be

Works on a Debian stable T43/p on kernels 3.18 and 4.4.  I don't recall
if I ever used Debian's 3.14 kernel in there, though.

Check dmesg (kernel log), pay close attention to everything ACPI.  Check
thermal limits.  Check termal sensors, your thinkpad has a truckload of
them.

Your thinkpad might be in need of a thermal sink reseat (and if you do
that, have "Arctic Silver 5" or something equally good and
*non-conductive, non-reactive* on hand to replace the CPU thermal
compound).

> causing this?  Or at least, which part of the system might cause
> scaling_max_freq to be (re)set to 1GHz right after I force-set it to
> 1.83GHz?
> Would it be some daemon like systemd or rather the kernel?

thermald might do it, but we don't install that thing by default in
Debian AFAIK.

--
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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Re: Who's playing with scaling_max_freq?

Stefan Monnier
[ FWIW, after changing the CPU from a T2400 to a T7600, I finally
  happened across some way to reduce the problem.  ]

>> causing this?  Or at least, which part of the system might cause
>> scaling_max_freq to be (re)set to 1GHz right after I force-set it to
>> 1.83GHz?
>> Would it be some daemon like systemd or rather the kernel?
> thermald might do it, but we don't install that thing by default in
> Debian AFAIK.

Not sure exactly what controls it, but at least I found out that there
is in the BIOS a setting for thermal management where I can choose
between "balanced" and "performance" (if memory serves) and which talks
about throttling.

And changing it did make a significant difference (I still can't
compile Emacs without triggering throttling, but it takes a lot longer
before it kicks in).


        Stefan

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