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Saving power on a laptop running Kubuntu 7.10 (Gutsy Gibbon)

Submitted by specialj on Sat, 10/20/2007 - 01:25.

Upon upgrading my laptop I decided to take advantage to the availability of the powertop application to try and reduce the power consumption of the laptop. I was able to reduce idle power consumption from about 20 watts down to about 14 watts which is a pretty significant improvement. I’ve documented the various changes I made to achieve those results.

Reducing wakeups from the video driver

My laptop uses the radeon driver which was causing the largest number of wakeups on my laptop. I followed instructions to drastically reduce this number by turning off DRI in the file /etc/X11/xorg.conf.

  1. sudo nano /etc/X11/xorg.conf
  2. Locate: Section "Device"
  3. Add the line: Option "NoDRI" to the section
  4. Restart the X server (Ctrl+Alt+Backspace)

Removing unused modules

I have never used pcmcia and I rarely use any usb device so I decided to disable the modules needed for these subsystems entirely (knowing that I could always turn them on when needed).

  1. sudo nano /etc/modprobe.d/custom
  2. Add the line: blacklist usbcore
  3. Add the line: blacklist pcmcia-core
  4. Reboot the computer for these to take effect

Configuring power saving packages

Packages for automated power savings seem to be numerous and contradictory. Kubuntu has the package laptop-mode-tools required as a dependency but it is not enabled. First I removed other more obsolete packages:

  • sudo apt-get remove powernowd
  • sudo apt-get remove laptop-mode

Then I enabled laptop-mode through acpid:

  • sudo nano /etc/default/acpi-support
  • set: ENABLE_LAPTOP_MODE=true

Then I set laptop-mode to control cpu frequency parameters:

  • sudo nano /etc/laptop-mode/laptop-mode.conf
  • set: CONTROL_CPU_FREQUENCY=1
  • also had to set various MAXFREQ and MINFREQ variables to match my cpu frequency scaling levels (which was available at cat /sys/devices/system/cpu/cpu0/cpufreq/scalingavailablefrequencies) as well as all the GOVERNOR settings to ondemand.

Configuring wireless driver

My wireless device uses the ipw2200 module and luckily there seems to be support for this module in laptop-mode-tools.

  • sudo nano /etc/laptop-mode-tools/conf.d/wireless-ipw-power.conf
  • set: CONTROL_IPW_POWER=1

Verify noatime option set on filesystems

  • sudo nano /etc/fstab
  • Make sure that all file systems have the noatime option set

Conclusions

There are still probably some areas to improve but this was a good start. It is disappointing that more of these options are not enabled by default. If they were Ubuntu would probably have a much more impressive showing in battery tests. My understanding is that since some options can be problematic on certain computer models they are often disabled by default. Unfortunately I have not found a really good tool for novices to use that has sensible defaults and the ability to change specific settings should they be problematic. This is definitely an area that needs some work.

Further readings

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