Androids: The Team That Built the Android Operating System

by Chet Haase

The kernel is a combination of the interface between the actual hardware and the rest of the system, plus everything that an OS has to do to make everything run (like boot up the system, create processes,68 manage memory, and handle communication between processes).

Hardware communication is handled by device drivers in the kernel, which are software modules that talk to the actual hardware on a device.

So Arve added the concept of wake locks to Android’s Linux kernel, to ensure that screen-off didn’t mean completely-off. Android would aggressively put applications and most of the system to sleep when the screen turned off (because battery consumption was always a huge concern), but wake locks ensured that the system could stay in a wakeful state if there was something happening that needed to continue even if the screen turned off.

A governor in an OS is the mechanism by which the speed, or frequency, of the CPU is changed to save power. For example, if your CPU is running really fast, then it is consuming more power and thus more battery.