2009/310 Disk IO PM Enhancement

[Terry (Sarito) Whatley]

Edward Pilatowicz wrote:
> On Tue, May 19, 2009 at 07:09:04PM -0700, Pawel Wojcik wrote:
>   
>> On 05/19/09 06:23 PM, Edward Pilatowicz wrote:
>>     
>>> On Tue, May 19, 2009 at 10:37:45AM -0700, Terry Whatley wrote:
>>>
>>>       
>>>>      4.3.4 disk power attribute driver properties
>>>>
>>>> 	sd(7D) will export a set of driver properties to indicate a disk's
>>>> 	power attributes. See Table-2.
>>>>
>>>> 	Table-1 Disk Power Attribute Properties (array properties are indexed
>>>> 		by power state in order of ascending power levels)
>>>> 	------------------------------------------------------------------------
>>>> 	Prop Name            Prop Type    | Prop Description
>>>> 	------------------------------------------------------------------------
>>>> 	"pm-resource-type"      String    | "resource-spindle-disk" for the
>>>>                                           | spindle disks
>>>> 	------------------------------------------------------------------------
>>>> 	"pm-perf" Integer array           | array of average R/W
>>>>                                           | performance percentages
>>>> 	------------------------------------------------------------------------
>>>> 	"pm-pwr-saving"  Integer array    | array of average power saving in
>>>>                                           | units of 0.1watt
>>>> 	------------------------------------------------------------------------
>>>> 	"pm-latency"     Integer array    | array of time to first data in units
>>>>                                           | of 100ms
>>>> 	------------------------------------------------------------------------
>>>>
>>>>
>>>>         
>>> exporting performance statistics via device properties seems weird to
>>> me.  is there a precedent for this?  why isn't this information being
>>> exported via kstats?  do we really want to train users to start using
>>> prtconf -v to get performance data?
>>>
>>> ed
>>>
>>>       
>> I think these are not performance statistics. I believe that these are
>> static arrays that are specific for a device type (most likely Sun disks
>> only), that correlate specific power level with performance and power
>> savings. These properties, I believe, are to be used by a storage power
>> manager to decide at what power level disk should run at given time.
>> Jane Chu may correct me here...
>> -Pawel
>>
>>     

That is correct.
>
> if that's the case then having them as device properties seems ok, but
> documentation for these properties should make it clear that these are
> not actual system performance numbers.
>
> ed
>   
As consolidation private interfaces, these will not be documented, aside 
from this case.

-sarito