Observations on power management

"Don't offer the choice of disabling compositing when on battery. It reduces functionality for no power benefit."

This one only becomes true with 2.6.28 or so, when all the vblank fixes in the drm drivers (intel and ati mainly) are in. Before it, it seems that composite/3D desktop triggers an amount of wakeups per second that equals the refresh rate, regardless of idleness. It's been fixed in drm trunk for over a year, but only with 2.6.28 the backlog started to really flow into Linus' kernel (I think. At least GEM went in.).

"Seeking takes more power than simply reading a linear set of blocks off a drive. It also kills performance - even a high spec drive will be unlikely to be able to perform more than 150 seeks a second."

I hope everyone developing eg. anything related to X, Compiz, KDE or GNOME startup reads this... otherwise we'll be stuck with the current boot+login time problems for the next 5-10 years until every root filesystem drive has been replaced with an SSD drive.