RE: cpufreq: intel_pstate: HWP mode issue

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

On 2020.07.08 07:54 srinivas pandruvada wrote:
> On Wed, 2020-07-08 at 07:41 -0700, Doug Smythies wrote:
> > On 2020.06.30 11:41 Doug Smythies wrote:

...

> > > If the short sleep is somehow simultaneous with some sort of 5.0
> > > millisecond (200 Hertz)
> > > periodic event (either in HWP itself, or via the driver, I am
> > > unable to determine which,
> > > but think it is inside the black box that is HWP),
> >
> > I have been attempting to characterise the "black box" that is HWP.
> > In terms of system response verses EPP, I only observe the HWP loop
> > time as the
> > response variable.
> >
> > 0 <= EPP <= 1 : My test can not measure loop time.
> > 2 <= EPP <= 39 : HWP servo loop time 2 milliseconds
> > 40 <= EPP <= 55 : HWP servo loop time 3 milliseconds
> > 56 <= EPP <= 79 : HWP servo loop time 4 milliseconds
> > 80 <= EPP <= 133 : HWP servo loop time 5 milliseconds
> > 134 <= EPP <= 143 : HWP servo loop time 6 milliseconds
> > 144 <= EPP <= 154 : HWP servo loop time 7 milliseconds
> > 155 <= EPP <= 175 : HWP servo loop time 8 milliseconds
> > 176 <= EPP <= 255 : HWP servo loop time 9 milliseconds
> >
> > If there are other system response differences within
> > those groups, I haven't been able to detect them,
> > but would be grateful for any further insight.
> >
> > Otherwise, in future, I do not see a need to test anything
> > other than 9 values of EPP, one from each group.
> >
> Thanks Doug,
> I think they are enough. But there is no guarantee that every CPU model
> will have same results as the power curve will be different.

Yes, of course the response curve is different between CPU models.

However, the basic loops times seem to be the same.
Although I admit to having limited data from other CPU models.

... Doug