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cpuidle - Do nothing, efficiently...

Adam Belay (abelay@novell.com)

Until now, most of the focus in Linux CPU power management has been on active CPU power management. cpufreq, which changes the processor frequency and/or voltage and manages the CPU performance levels and power consumption based on CPU load. Another dimension of CPU power management is CPU idling power. In general, there is now more focus shifting towards idle power (Energy star) and new platforms/processors are supporting multiple idle-states with different power and wakeup latency characteristics. Today most of the mobile processors support multiple idle states with varying amount of power consumed in those idle states and each state has an entry-exit latency associated. This emphasis on idle power necessitates the need for a generic Linux kernel framework to manage idle CPUs.

This paper covers 'cpuidle' - an effort toward a generic idle framework in the Linux kernel. The goal is to have a clean interface for any platform to make use of different CPU idle levels and also to provide abstraction between idle-drivers and idle-governors allowing for independent development. The target audience includes those who have a general interest in idle processor power management and its impact on battery life, developers who would like to create new and better governors, and developers interested in utilizing the cpuidle infrastructure on new platforms.

Paper is in collaboration with Shaohua Li at Intel and Venkatesh Pallipadi at Intel.