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HOWTO CHANGE POWER MANAGEMENT

Ubuntu use "powernow" deamon to scale processor frequency. You can change the mode of frequency scalling with the "powernowd" software.

There are 4 modes supported by this powernowd:

  • Mode 0, SINE, changes the frequency as a sine wave function, raising
the frequency by "step" Hz every time the CPU usage goes over 80%, and
decreases it by "step" Hz when the CPU usage falls under 20%.

  • Mode 1, AGGRESSIVE, changes frequency by a sawtooth function. Imme‐
diately jumps to the highest frequency whenever CPU usage goes over
80%, and decreases by "step" Hz as usage drops below 20%. This is the
default behavior.

  • Mode 2, PASSIVE, is the inverse of AGGRESSIVE. Immediately jump to
lowest frequency when usage drops below 20%. Raise by "step" Hz if it
goes above 80%.

  • Mode 3, LEAPS, immediately jumps to the highest frequency if usage is
above 80%, and immediately jumps to the lowest frequency if usage is
below 20%.

You use the software like that (root session ! ):
#powernowd -m 0
--->you set mode 0

You can have more information if you type :
# man powernowd



HOWTO USE FREQUENCY SCALING GOVERNORS

A Short Overview over the available governors:
  • ondemand This driver is a dynamic cpufreq policy governor. It changes frequency based on the processor load
  • conservative Similar to ondemand but has a much slower 'slew rate', remaining at high frequency for many seconds after recent processor demand.
  • powersave Like the name says, your battery would choose this one;). It sets the Frequency always to the lowest available.
  • userspace You have to choose this one, if you want to set the frequency manually.
  • performance This governor sets your Frequency always to the highest available.

Happyness, on feisty farm we have the 4 governors, and you can choose wich one you want like that :
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
--->show governors for cpu0
#cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
---> see the governor for cpu1 (ondemand at the beginning)

#echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
#echo powersave > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
--->put powersave for cpu0 and cpu1

I recommend ondemand for normal use and powersave on the road...
You can use this script to switch between ondemand and powersave :
# gedit mcpu <-----copy script inside
#chmod 755 mcpu
#cp mcpu /usr/bin
After you can create a DesktopShortcut with "sudo mcpu" with the "console launch" option... ( sudo because you must be root to use this script )



You can find more information about power on this website or there ...


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collins_ 		Latest page update: made by collins_ , Mar 31 2007, 6:32 AM EDT (about this update About This Update collins_ Edited by collins_

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