Re: [linux-pm] [RFC PATCH V3 4/4] cpuidle: Single/Global registrationof idle states

From: Trinabh Gupta
Date: Thu Apr 21 2011 - 00:53:43 EST




On 04/20/2011 11:03 PM, Kevin Hilman wrote:
Trinabh Gupta<trinabh@xxxxxxxxxxxxxxxxxx> writes:

With this patch there is single copy of cpuidle_states structure
instead of per-cpu. The statistics needed on per-cpu basis
by the governor are kept per-cpu. This simplifies the cpuidle
subsystem as state registration is done by single cpu only.
Having single copy of cpuidle_states saves memory. Rare case
of asymmetric C-states can be handled within the cpuidle driverand
architectures such as POWER do not have asymmetric C-states.

I haven't actually tested this series on OMAP yet, but it currently
doesn't compile.

Hi Kevin,

Yes, I tested it only for x86 (as I had mentioned in the description
of the patch series). I just wanted to get comments on the design
and understand how it affects various architectures in question. It
looks to me as if the design should be okay and infact better for
architectures like ARM since they do not have different idle
states for different cpus and thus do not require per-cpu registration.
Global registration would work and be simpler; please correct me if I am
wrong.


The patch below (on top of your series) is required to compile on OMAP,
I think it's doing what you intended, but please confirm.

Thanks for helping with this.

-Trinabh
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