RE: [PATCH V6 1/3] cpufreq: intel_pstate: configurable algorithm to get target pstate

["Doug Smythies" <dsmythies@telus.net>]

On 2015.12.15 02:30 Philippe Longepe wrote:
> On 14/12/2015 23:13, Doug Smythies wrote:
>> On 2015.12.14 08:15 Stephane Gasparini wrote:
>>
> In the table sent by stephane, "performance" meant "original algorithm" 
> based on average pstate (aperf/mperf).

Oh.

> On Atoms, a setpoint of 60 is not too high. With higher setpoints we'll 
> not be able to reach meet some performance KPIs

Define "KPI"

> (some frames are dropped mainly for gaming use cases). However, we are 
> working on a more power conservative algorithm).

I do not think the issue / challenge is specific to Atom.

>>
>> I think that a more comparable test would be a 50% (or whatever) load
>> calibrated to a nominal CPU frequency (I use the max non-turbo CPU
>> frequency, but it can be anything.) Meaning that the once the fixed
>> packet of work is done, the CPU can go idle sooner or later, depending
>> on the CPU frequency.
> Are you using an existing tool for doing that or did you developed your 
> own tool ?

While he would not recognize it now, I mainly use a simple program that
Peter Zijlstra gave me a few years ago, consume.c. However, I added fixed
work packet mode, to satisfy a need for something more representative of
real world periodic workflows.

I'll send it to you off-list.

On 2015.12.15 05:07 Stephane Gasparini wrote:

> Well you misunderstood the power numbers I guess
> e.g. if you watch a movie for 1h30, it will last 1h30 not matter what is the 
> average power, so the lower is the average power the better it is.

O.K. I didn’t know all of those tests had to run for whatever time.
But for the performance list of tests, there is no energy information.
I'm just saying that it might matter for some, as in ffmpeg example I gave.

> Here are the detail for Application install
>
> Intel PState    Intel PState    
> Performance     CPU Load      
> ≅ 799 mW (28 s)	≅ 383 mW (34 s)
> ≅ 29 mW/s	≅ 11 mW/s

Wouldn't the correct terminology be 22.4 Joules and 13.0 Joules
to do the job?
Or 42% energy saved at a cost of 21% extra time.

Anyway, you made your point.

... Doug