Dear all,
Q: In order to tune the math library ATLAS http://math-atlas.sourceforge.net/ , I need to set the all CPU cores with the same frequency. http://math-atlas.sourceforge.net/at...all/node5.html
Unfortunately I was not able to do that, because
What is not done
CPU throttling (ACPI T-States)
While this can be useful for systems which tend to overheat, it is not an option to save power. Most hardware itself (CPUs) has a good overheat detection and are doing throttling on their own when a certain temperature is reached.
The main reason behind why the operation system (kernel/userspace) is not doing it is that throttling doesn't give you any power savings. The CPU just skips some clock ticks without actually reducing the frequency. It just makes the system slow which in turn means that tasks require more time to finish up keeping the whole system busy. Don't do that on your own!
Can I ... ? install another cpu driver "acpi-cpufreq" by myself, which offers the "userspace" governor , or any other trick as the workaround? :\
PS, here is an old thread https://forums.opensuse.org/showthre...cpu-throttling. The C.F.U. - CPU Frequency Utility cannot solve the problem.
Thanks in advance!
gundamlh
Q: In order to tune the math library ATLAS http://math-atlas.sourceforge.net/ , I need to set the all CPU cores with the same frequency. http://math-atlas.sourceforge.net/at...all/node5.html
Unfortunately I was not able to do that, because
Quote:
What is not done
CPU throttling (ACPI T-States)
While this can be useful for systems which tend to overheat, it is not an option to save power. Most hardware itself (CPUs) has a good overheat detection and are doing throttling on their own when a certain temperature is reached.
The main reason behind why the operation system (kernel/userspace) is not doing it is that throttling doesn't give you any power savings. The CPU just skips some clock ticks without actually reducing the frequency. It just makes the system slow which in turn means that tasks require more time to finish up keeping the whole system busy. Don't do that on your own!
- 2. I'm using openSUSE 13.1 and it uses driver intel_pstate which provides only two CPU scaling governors, "powersave" and "performance" rather than "userspace"
Code:
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to http://bugs.opensuse.org, please.
analyzing CPU 0:
driver: intel_pstate
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 0.97 ms.
hardware limits: 1.20 GHz - 3.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 1.20 GHz and 3.60 GHz.
The governor "performance" may decide which speed to use
within this range.
analyzing CPU 1:
driver: intel_pstate
CPUs which run at the same hardware frequency: 1
CPUs which need to have their frequency coordinated by software: 1
maximum transition latency: 0.97 ms.
hardware limits: 1.20 GHz - 3.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 1.20 GHz and 3.60 GHz.
The governor "performance" may decide which speed to use
within this range.
analyzing CPU 2:
driver: intel_pstate
CPUs which run at the same hardware frequency: 2
CPUs which need to have their frequency coordinated by software: 2
maximum transition latency: 0.97 ms.
hardware limits: 1.20 GHz - 3.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 1.20 GHz and 3.60 GHz.
The governor "performance" may decide which speed to use
within this range.
analyzing CPU 3:
driver: intel_pstate
CPUs which run at the same hardware frequency: 3
CPUs which need to have their frequency coordinated by software: 3
maximum transition latency: 0.97 ms.
hardware limits: 1.20 GHz - 3.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 1.20 GHz and 3.60 GHz.
The governor "performance" may decide which speed to use
within this range.PS, here is an old thread https://forums.opensuse.org/showthre...cpu-throttling. The C.F.U. - CPU Frequency Utility cannot solve the problem.
Thanks in advance!
gundamlh