Revision of Optimizing battery time from Thu, 12/04/2014 - 16:56

This wiki page has tips on reducing your computer's electricity consumption. If you're using a laptop, it will help extend your battery life.

We tested these tips on a computer running Trisquel 6. Trisquel 6 is based on Ubuntu 12.04 LTS. The same information should be applicable to Debian, Trisquel 7, Ubuntu 14.04 LTS, and other Debian derivatives.

Tips & tricks

• Suspend the system when you're not using it.
• In the BIOS, disable every device that you don't plan to use. For example disabling all the following would save you around 2W:
  • Ethernet (if you only/mostly use wireless)
  • Wireless devices (your computer may have hardware switches for these):
    • Bluetooth
    • WiMAX
    • Wireless WAN (3G)
    • Wifi
  • The touchpad (on a laptop)
  • Sound card (estimated 2W savings):
    • 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".

• Disable wake-on-lan --which keeps the LAN port active (estimated 1W savings).

• Check your power usage statistics with the gnome-power-statistics command

• Set your system to reduce the screen brightness after a set amount of inactivity. This can be done in Trisquel Menu -> System Settings -> Brightness and Lock. Change the "Turn off screen when inactive for:" setting to the desired time.

• Use a solid state disk drive (SSD) - they use less electricity than regular hard disks.

Useful Packages

• Linux-libre (homepage): Upgrade your kernel to its latest version following this guide: trisquel.info/wiki/update-linux-libre-kernel.
• 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, the SD card reader, a joystick or your sound card? Disable the corresponding kernel modules by adding to /etc/modprobe.d/blacklist.conf

blacklist bluetooth
blacklist firewire_core (FireWire, or IEEE 1394)
blacklist firewire_ohci
blacklist yenta_socket
blacklist joydev
blacklist sdhci (SD card)
blacklist sdhci_pci
blacklist dm_crypt
blacklist tifm_7xx1
blacklist shpchp
blacklist btrfs

Now, 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? Get rid of them by removing /etc/init/tty3.conf ... /etc/init/tty6.conf, reboot.

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