Why did my power usage increase with dynticks? Why do I never reach sleep states deeper than C2?
The current ACPI sleep function requires wakeups to reach deeper sleep states. Certain drivers, such as ipw2200, limit the initial sleep state to C2 due to DMA activity. With dynticks, which tries to sleep as long as possible, this means that your processor will, most of the time, only reach C2 and thus waste power compared to a non-dynticks kernel if it is mostly idle. This will be solved by an upcoming cpuidle patch. Until this hits mainline, you should compare your power usage with and without dynticks (and maybe with different HZ values) to figure out which is currently the best for your workload.
