Saving power with Linux on Intel hardware

Linux power usage progress

In the last two months, Linux has made an enormous step forward in terms of power consumption and battery life. Linux kernel community developers such as Thomas Gleixner and Ingo Molnar and various Intel developers joined hands in developing a set of patches to push Linux to the next level with the Tickless Idle feature and a series of follow on developments that cash in the potential of the tickless core infrastructure.

It is hard to show "one size fits all" numbers, since each laptop or server model has different components and BIOS settings; in order to show some actual data on the progress we have to pick an example machine and measure that.

In our measurements, we used a T61 laptop (with a 15" inch screen and Intel graphics adapter). The laptop AC adapter was plugged into the power meter device; the power measured is thus the "real" power, including the power that gets consumed by the power supply of the laptop.

To avoid skewing the measurement with power consumed with charging the battery (even if you are on AC power, the battery gets charged a little every once in a while), the battery was physically removed from the laptop. In addition, the measurements were all done when the laptop fan was off.

For all measurements, the screen brightness was set to the "minimum" brightness level that other operating systems also use when on battery. This is not the lowest level possible; however at lower levels the usability and readability of the screen is significantly less.

(Note: we're not trying to endorse one model over another; we're using the T61 since this was the first laptop with the new 965 chipset that became available on the market)

Tickless is unfortunately not merged into the x86-64 architecture in kernel.org kernels, but you can get the patch for this here. This patch hopefully will go into the 2.6.23 kernel.