Get the most of the battery

From EasyPeasy Wiki

These changes allow the CPU to sleep for longer when idle, saving power. For more information see the website for the "powertop" tool, http://www.lesswatts.org/projects/powertop/

Contents 1 force-hpet 2 CPU Frequency scaling 3 Laptop-mode 4 15 sec dirty_writeback_centisecs 5 15 sec ext3 commit interval

[edit] force-hpet

Note that this does not appear to be necessary if you use the Ubuntu Eee distribution.

• Open up a terminal and write:

  sudo gedit /boot/grub/menu.lst

• Find the line that looks something like this:

  # defoptions=quiet splash

• And add "force-hpet" at the end so it looks something like this:

  defoptions=quiet splash force-hpet

• Save the file. When you're back in the terminal write:

  sudo update-grub

• This takes effect next time you restart the laptop

[edit] CPU Frequency scaling

(Note that this seems not to be necessary when using ubuntu-eee 8.04)

• Edit /etc/modules

 sudo gedit /etc/modules

• Add the line

p4_clockmod

• Make sure powernowd is installed (I think it's by default) otherwise install it using

 sudo apt-get install powernowd

[edit] Laptop-mode

Alternatively enable laptop-mode

• Enable laptop mode by editing /etc/default/acpi-support

  ENABLE_LAPTOP_MODE=true

• Edit /etc/laptop-mode/laptop-mode.conf

  ENABLE_LAPTOP_MODE_ON_BATTERY=1

• Disable all HD features as eeepc uses a SSD

  CONTROL_HD_XXX=0

• Tune the cpu scaling options, too aggressive settings will make performance too slow. This setting works ok:

  BATT_CPU_GOVERNOR=performance

You can check the current cpu frequency with

 cat /proc/acpi/processor/CPU1/throttling

Whit these settings, the cpu stays mostly at 50%, and increases imediatly by demand, like when opening webpages in firefox.

[edit] 15 sec dirty_writeback_centisecs

This reduces how often linux writes data to HDD. The value is in 100'ths of a second. Thus 1500 is 15 seconds. See http://www.westnet.com/~gsmith/content/linux-pdflush.htm

• Open up a terminal and write:

  sudo gedit /etc/sysctl.conf

• Add the line:

  vm.dirty_writeback_centisecs=1500

• This takes effect next time you restart the laptop

[edit] 15 sec ext3 commit interval

This is useful if you use the EXT3 filesystem. EXT3 is a journaling filesystem, which means it will write its journal to the disk by default every 5 seconds.

See man mount. commit=nrsec - Sync all data and metadata every nrsec seconds. The default value is 5 seconds. Zero means default.

• Open /etc/fstab

  sudo gedit /etc/fstab

• Find root filesystem. It is something like:

  UUID=e50b7067-d585-49e0-af2b-167649dda172 / ext3 defaults,errors=remount-ro 0 

• Add the commit option "commit=15"

  UUID=e50b7067-d585-49e0-af2b-167649dda172 / ext3 defaults,errors=remount-ro,commit=15 0