[tesla-dev] Observing CPU C-state info with ...?

[Bill Holler]

Eric Saxe wrote:
> Alexander Kolbasov wrote:
>> Bill Holler <Bill.Holler at sun.com> wrote:
>>
>>
>>     Bill> It will be useful to have c-state information observable 
>> (including latency
>>     Bill> and power savings) during development and testing.  Should 
>> c-state
>>     Bill> information be in a kstat such as the cpu_info kstat?
>>
>> Isn't c-state information extremely transient? I am wondering what value
>> can you get if it is placed in kstats. IMO something like total time in
>> various states might be more useful (if it is possible to obtain).
>>   
> PowerTop conveys the total time in various c-states (over a given 
> sampling interval). I'm not sure how useful the "total time since the 
> system  booted" would be, since that would probably include periods of 
> time where the system was busy.
>
> -Eric
>
My thoughts were that most cpus spend more time in an idle c-state than
executing in a p-state.

Sounds like PowerTop has much of the c-state info.  Latency and power-
savings per c-state is probably not useful to users, and we can get at this
groping around with mdb.

Bill