Revision of Optimizing battery time from Thu, 11/21/2013 - 04:38

The information here will help your computer use less electricity. If you're using a laptop, it will help extend your battery life.

We tested this informaton on a computer running Trisquel 6. Trisquel 6 is based on Ubuntu 12.04 LTS.

Tips & tricks

• Suspend the system when you're not using it
• In the BIOS, disable every device that you don't plan to use: Bluetooth, WiMAX, Wireless WAN (3G), touchpad (~2W total savings), and specially wake-on-lan which keeps the LAN port active (1W savings);
• Check your power usage statistics with the gnome-power-statistics command
• For your screen: set an automatic decrease of the luminosity after some time of inactivity;
• Deactivate the Bluetooth/Wifi when not using it (for a long time). Your computer may have hardware switches for these;
• Solid state drives require less electricity than hard disk drives;
• Disabling the sound card will save around 2W -- up to 5% battery life
  • Right-click on the speaker in the task bar and choose "Sound preferences"
  • In the "Hardware" tab, click on your sound card, then select the profile "Off"

Useful Packages

• Linux-libre (homepage): Upgrade your kernel to latest Linux-libre. There are two PPAs making this available (based on a forum discussion about both):
  • Linux-libre Package Team PPAs (PPA, test): specific for Ubuntu-based distributions;
  • a PPA maintained by jxself: targeting any Debian-based distro.
• laptop-mode-tools (homepage) : Tools for Power Savings based on battery/AC status
  Laptop mode is automatically enabled after installing this package. Check the ArchLinux extensive documentation about this.
• powertop (homepage) - tool to find out what is using power on a laptop
• rovclock - utility to control frequency rates of your Radeon card
  Check the Thinkwiki rovclock documentation about this package
• If you use a HDD, put your Abrowser profile on a ramdisk to avoid spinning the platter. Trisquel comes automatically with a ramdisk at /dev/shm. Note that the ramdisk is volatile, you might want to backup the profile before restarting/shutting down.

Blacklist kernel modules

Do you never or seldom use things like Bluetooth, sd card reader, joystick or your sound card? Disable the corresponding kernel modules by adding to /etc/modprobe.d/blacklist.conf

blacklist bluetooth
blacklist firewire_core
blacklist firewire_ohci
blacklist yenta_socket
blacklist joydev
blacklist sdhci
blacklist sdhci_pci
blacklist dm_crypt
blacklist tifm_7xx1
blacklist shpchp
blacklist btrfs

And then run sudo update-initramfs -u and restart. You can find out what modules are loaded using the lsmod command. If you want a very terse info about a module, you can sudo modinfo modulename. These modules might get automatically loaded when actually needed or if not, you can sudo modprobe modulename to insert.

Remove excess VTs

Do you use virtual terminals 3-6? I don't, so I got rid of them by removing /etc/init/tty3.conf ... /etc/init/tty6.conf then I rebooted.

Runtime PM

When you run powertop you may notice that many devices have runtime power management disabled. You can enable them all by echoing auto to their control files as super user, e.g. in a startup script. You can find a list of such files with ls /sys/bus/{pci,i2c}/devices/*/power/control

PCIe ASPM

Some newer hardware and BIOSes support PCIe active state power management. You can check dmesg|grep -i aspm to see how your system is doing. You can try forcing it by adding to grub configuration, on the kernel line pcie_aspm=force and then running update-grub and rebooting. Watch out for hangs.

References and useful links

• "Squeezing battery time" forum discussion
• http://chroot-me.in/blog/index.php/blog/26