Messages in this thread | | | Date | Wed, 7 Oct 2009 16:56:48 +0530 | From | Vaidyanathan Srinivasan <> | Subject | Re: [v7 PATCH 0/7]: cpuidle/x86/POWER: Cleanup idle power management code in x86, cleanup drivers/cpuidle/cpuidle.c and introduce cpuidle to POWER. |
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* Peter Zijlstra <a.p.zijlstra@chello.nl> [2009-10-06 20:04:39]:
> On Tue, 2009-10-06 at 22:05 +0530, Arun R Bharadwaj wrote: > > > Also, the per-cpu nature of registration/unregistration of cpuidle > > has been maintained as ACPI needs this. > > Right, so can't we ditch that and have acpi default to the lowest common > C-state and warn when various cpus report different C-states?
Hi Peter,
As Arjan mentioned previously, the per-cpu registration has to stay for x86 for now due to legacy ACPI compatibility. Breaking that may break lot of existing users and we do not have a clean fallback method.
As far as powerpc is concerned, we can work with a single global registration. However we would like to have the same interface across different archs.
With the new re-factoring (v7), Arun has killed most of the list traversal and linking between various cpu's cpuidle_driver structures. Now we have a per-cpu stack of registered devices and we lookup the structs using online cpumasks. The cpuidle_driver structure has list of idle routing pointers (struct cpuidle_state) and rest of it is statistics that needs to be maintained at a per-cpu level anyway. All that is duplicated here is the array of idle routines (struct cpuidle_state) on each cpu.
The objective of the refactoring is to have a single common idle routine management framework (remove pm_idle) and we have it done through cpuidle registration framework. We can incrementally remove the per-cpu registration later easily by splitting the cpuidle_driver structure.
--Vaidy
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