Managing Power
For devices operating on battery power, power management is critical. Anything we can do to reduce power usage will increase battery life. Even for devices running on mains power, reducing power usage lowers energy costs and decreases the need for cooling. In this chapter, I will introduce the four principles of power management:
- Don’t rush if you don’t have to.
- Don’t be ashamed of being idle.
- Turn off things you are not using.
- Sleep when there is nothing else to do.
In more technical terms, the power management system should reduce the CPU clock frequency. During idle periods, it should choose the deepest sleep state possible; it should reduce the load by powering down unused peripherals; and it should put the whole system into a suspended state while ensuring power state transitions are quick.
Linux has features that address each of these points. I will describe each one in turn with examples and advice...
