[$] Improving idle behavior in tickless systems

Most processors spend a great deal of their time doing nothing, waitingfor devices and timer interrupts. In these cases, they can switch to idlemodes that shut down parts of their internal circuitry, especially stoppingcertain clocks. This lowers power consumption significantlyand avoids draining device batteries. There are usuallya number of idle modes available; the deeper the mode is, the less power theprocessor needs. The tradeoff is that the cost of switching to and fromdeeper modes ishigher; it takes more time and the content of some caches is also lost. In theLinux kernel, the cpuidle subsystem has the task of predicting which choicewill be the most appropriate. Recently, Rafael Wysocki proposeda new governor for systems with tickless operation enabled that isexpected to be more accurate than the existing menu governor.