Improving idle behavior in tickless systems
Improving idle behavior in tickless systems
Most processors spend a great deal of their time doing nothing, waiting for devices and timer interrupts. In these cases, they can switch to idle modes that shut down parts of their internal circuitry, especially stopping certain clocks. This lowers power consumption significantly and avoids draining device batteries. There are usually a number of idle modes available; the deeper the mode is, the less power the processor needs. The tradeoff is that the cost of switching to and from deeper modes is higher; it takes more time and the content of some caches is also lost. In the Linux kernel, the cpuidle subsystem has the task of predicting which choice will be the most appropriate. Recently, Rafael Wysocki proposed a new governor for systems with tickless operation enabled that is expected to be more accurate than the existing menu governor.