[Beowulf] Prevention of cpu frequency changes in cluster nodes (Was : cpupower, acpid & cpufreq)

[Skylar Thompson]

On 06/09/2013 11:35 AM, Mikhail Kuzminsky wrote:
> I installed OpenSuSE 12.3/x86-64 now. I may now say about the reasons
> why I am afraid of loading of cpufreq modules.
> 
> 1) I found in /var/log/messages pairs of strings about governor like
> 
> [kernel] "cpuidle: using governor ladder"
> [kernel] "cpuidle: using governor menu"
> 
> and strange for me
> [kernel] ENERGY_PERF_BIAS: Set to 'normal', was 'performance'
> [kernel] ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8)
> 
> 2) The presence on installed system of /sys/devices/system/cpu/cpufreq
>                               /sys/devices/system/cpu/cpu0/cpuidle
>      directories. cpuidle directories contains state0, state1 etc
> directories w/non-empty files.
> 
> 3) But to prevent  cpu frequency changes I suppressed all like
> possibilities in BIOS.
> 4) And I don't have (as I wrote in my previous Beowulf message)
> /sys/devices/system/cpu/cpu0/cpufreq files.
> 
> Just the presence of this file is used by my /etc/init.d/cpufreq script
> as test of needs to load cpufreq kernel modules.
> 
> 5) lsmod says that there is no cpufreq modules loaded.
> Any comments ? Am I everywhere here right and should I ignore my afraids
> about kernel messages and presence of some
> /sys/devices/system/cpu/...... files ?

Can you use the performance governor instead? That should lock the clock
rate to the maximum supported by the hardware. Something like this at
boot would do the trick:

for CPU in $(awk -F: '$1 ~ /^processor/ {print $2}' /proc/cpuinfo);do
    sudo /usr/bin/cpufreq-set -c ${CPU} -g performance
done

Depending on the system, you might be able to do this via a BIOS setting
too, by removing support for OS-set CPU clock rate.

Skylar