>> What data do we want in these accessor interfaces?
>> This data is available:
>>    1) max-idle duration via LAPIC Current Count register.
>>     
>
> Is this always from LAPIC? What if you enter a deep c-state and you rely on 
> other timer sources?
>   

Lets keep the interface platform and implementation agnostic.
The max-idle duration could come from anywhere.   :-)


> Anyway anticipated max duration of sleep is useful.
>
>   
>>    2) last idle duration
>>     
>
> Probably #2 along with previous anticipated actual? Just to know if we could 
> auto-demote?
>
>   
>>    3) possibly a running average idle time
>>    4) ACPI round trip latency of the current target idle-State.
>>    5) intr rate calculation.
>>    6) target C-State.
>>     
>
> Does the target c-state really matter? Or do we need just item #4 above?
>   

Yes, #4 seems more useful than #6.

Regards,
Bill

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