Modifying CPU Power State (C-state)

(Doc ID 1559908.1)

Last updated on MAY 10, 2017

Applies to:

Linux OS - Version Oracle Linux 5.0 to Oracle Linux 6.4 [Release OL5 to OL6U4]
Information in this document applies to any platform.


CPU power states, also known as C-states - define the degree to which the processor core is allowed to "sleep". C0 indicates a normal operation. All other C-states (C1-Cn) are states where the processor clock is inactive (cannot execute instructions).  In these inactive states, different parts of the processor are powered down. Although Deeper C-states allow the processor to consume less power, they also have longer exit latencies (the time to transition back to C0) which can be disruptive to certain operating system functions and application timers.  Therefore it is sometimes recommended to limit or disable the CPU power state altogether in order to avoid these latencies.


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