In part 1 of this series we learned how to measure how much power our systems are using, both hardware and software, and some tricks for reducing power usage without degrading performance. Today we're going to dive into the world of power management on laptops: ACPI, APM, hard disk spindowns, and spinups.
A friend had an interesting problem for me to solve; he wanted to know how to turn off his laptop’s monitor without shutting down the system or waiting for it to go off. He wanted to leave it working during the night on the desk in his room, without the light from the LCD bothering him while he slept.
Since publishing our Ubuntu power tests, where we had monitored the power consumption of the past six Ubuntu releases going back two years on a laptop, we've had repeated requests for a power comparison between Windows and different Linux distributions. Well, in this article are the first set of results from that testing. We've compared the power consumption of Microsoft Windows XP, Windows Vista, Fedora 7, and Ubuntu 7.10.
Ubuntu 7.10 "Gutsy Gibbon" is due out in just a few days and shipping with it is the Linux 2.6.22 kernel. One of the interesting additions to the Linux kernel since the 2.6.20-based Ubuntu 7.04 "Feisty Fawn" release has been the tickless kernel feature. If you hadn't read out tickless kernel article from earlier this year, the tickless kernel feature (CONFIG_NO_HZ) is designed to improve the power efficiency especially on servers and portable devices.