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Old 05-11-2012, 12:32 AM   #1
rng
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CPU Frequency Scaling


How useful and important is cpu frequency scaling? I read somewhere that some larger distros have this already set up. How do I find out if it is activated in my installation and how much difference it is making? What will be the best/easiest application to monitor and adjust it. Thanks for your help.
 
Old 05-11-2012, 12:58 AM   #2
em31amit
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files in /sys/devices/system/cpu/cpu0/cpufreq/ provide information and a means of controlling the frequency scaling subsystem. Seed values are given in Khz. You need to be root to access the /sys filesystem.

Your max speed is at /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq.
Code:
    # cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq 
    700000
Your min speed is at /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq.
Code:
    # cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq 
    500000
 
Old 05-11-2012, 02:28 AM   #3
rng
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The response to these commands on my system is:
Code:
No such file or directory
So this is not set up on my installation. But is it worth adjusting it? Are there any drawbacks?
 
Old 05-11-2012, 04:40 AM   #4
em31amit
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what linux distribution are you using??? i hope this will work in rhel5+
 
Old 05-11-2012, 04:53 AM   #5
cascade9
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With older CPUs, frequency scaling will not work. Almost all distros will setup frequency scaling if its supported (so far as I know they all will, but there might be a few that dont).

*edit- of course arch (and other distros with similar driving ideas) wouldnt have it setup 'out of the box'.

What CPU are you running?

Last edited by cascade9; 05-11-2012 at 09:00 AM.
 
Old 05-11-2012, 08:30 AM   #6
rng
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My CPU is fairly recent:
Quote:
i686 Intel(R) Core(TM) i3 CPU 540 @ 3.07GHz GenuineIntel
I am using arch linux and I know cpu frequency scaling is not set up here. I want to know if it is worth all the trouble to set it up.

Last edited by rng; 05-11-2012 at 08:39 AM.
 
Old 05-11-2012, 08:55 AM   #7
cascade9
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I'd use it if your CPU supports it.

Frequency scalling helps with power use, tempratures and may give your CPU a longer lifespan.
 
Old 05-11-2012, 10:09 AM   #8
rng
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Quote:
I'd use it if your CPU supports it.
Which is the best application to monitor and configure cpu frequency scaling?
 
Old 05-15-2012, 10:14 PM   #9
speck
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Try the following as root or sudo (I think that CPU will have four entries):
Code:
modprobe acpi-cpufreq
modprobe cpufreq_conservative
echo conservative > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo conservative > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo conservative > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor
echo conservative > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor
To make sure it's working, they should all be listed as "conservative":
Code:
cat /sys/devices/system/cpu/cpu?/cpufreq/scaling_governor
 
  


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