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Linux Power Management Whys and Wherefores

Recently, Matthew Garrett, a developer who works with a number of open source projects, including Debian and Ubuntu, wrote a guide for good power management practices. Though he states the guide is mainly for those working with desktop environment implementation and power management interfaces and utilities, he points out a few hardware/software relationships that might interest the casual end-user.

He discusses some of the rather counter-intuitively named Linux kernel CPU governors ("powersave" and "performance") and the correlation (and dangers) of using tools designed for power management to control system temperatures. Garrett's summaries (in particular) are straightforward, and are probably of at least some interest to casual users who overclock or find hardware and operating system interaction on a conceptual level intriguing.

Garrett's observations on graphics hardware are enlightening. He states that regardless of whether a compositor (such as Compiz, or KDE4's Kwin compositor) is in use, a desktop is, most commonly, static. This is why, he says, both traditional desktops or desktops with any number of 3D effects enabled will assume roughly the same amount of power. In effect, if you've been disabling your compositor when switching to battery power on your notebook, it probably hasn't been doing a whole lot for battery life.

Garrett states that there isn't an operating system out there that's quite mastered the blanket optimization of power management. The tools exist to tweak to perfection, but the balance can be difficult to achieve -- and is ever changing, even on the same machine.

• hardware
• linux
• kernel
• power management
• powersave
• performance

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