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Hohoho

Member

Registered: 2007-06-23

Posts: 222

cpufreq-set doesn't change governor for both CPUs

I have Intel Core2 Duo T8100 (2.1GHz), Dell Inspiron 1520 laptop. I'm not even sure if this worked before, but now doing:

cpufreq-set -g performance

only switches the first CPU to the "performance" governor.
If I specifically tell it to switch the governor for each CPU it works fine.
I believe the problem to be because of this:

$ cpufreq-info 
cpufrequtils 005: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 0
  hardware limits: 800 MHz - 2.10 GHz
  available frequency steps: 2.10 GHz, 2.10 GHz, 1.60 GHz, 1.20 GHz, 800 MHz
  available cpufreq governors: userspace, conservative, powersave, ondemand, performance
  current policy: frequency should be within 800 MHz and 2.10 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.
analyzing CPU 1:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 1
  hardware limits: 800 MHz - 2.10 GHz
  available frequency steps: 2.10 GHz, 2.10 GHz, 1.60 GHz, 1.20 GHz, 800 MHz
  available cpufreq governors: userspace, conservative, powersave, ondemand, performance
  current policy: frequency should be within 800 MHz and 2.10 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.

"CPUs which need to switch frequency at the same time" doesnt say that both have to switch.
The only place that I found that could have any impact on this are these files in /sys:
/sys/devices/system/cpu/cpu0/cpufreq/affected_cpus
/sys/devices/system/cpu/cpu1/cpufreq/affected_cpus
Both return only the value of one processor, 0 and 1 accordingly, but not both.
I tried doing as root:

# echo "0 1" > /sys/devices/system/cpu/cpu0/cpufreq/affected_cpus 
bash: /sys/devices/system/cpu/cpu0/cpufreq/affected_cpus: Permission denied

also tried echo 1, echo 0, nothing is allowed.
And I found no sysctl key that regulates this, so at this point I'm at a loss what to do.
Except for this, everything else about cpufreq works perfectly fine.

I'm using latest packages from stable (using 2.6.29 kernel, was the same with 2.6.28).

Last edited by Hohoho (2009-04-11 16:50:51)

Fackamato

Member

Registered: 2006-03-31

Posts: 579

Re: cpufreq-set doesn't change governor for both CPUs

Same issue here - I have to add two cpufreq monitors on my gnome panel and change both manually when I want to switch from ondemand to performance, for example. Can't' change both at the same time...

.:B:.

Forum Fellow

Registered: 2006-11-26

Posts: 5,819

Website

Re: cpufreq-set doesn't change governor for both CPUs

You need to run the command once per core.

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R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: cpufreq-set doesn't change governor for both CPUs

If I recall correctly that is a feature of more modern Intel CPUs, specially the ones targeted to mobile devices. Each core is/should be able to work independently, this means different frequencies or even one or more can be turned off while other cores are still active.
Although that feature is nice it is a bit cumbersome to have to change the governor twice for each cpu ..... but nothing a nice simple script can't solve though

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R00KIE
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Hohoho

Member

Registered: 2007-06-23

Posts: 222

Re: cpufreq-set doesn't change governor for both CPUs

Thanks for the info, I suspected that it must be made that way on purpose since no substantial complaining could be found through Google.
My only caveat is the Gnome applet not being able to handle both CPUs at once.