Hi Lukasz,
On Mon, Nov 4, 2024 at 4:15 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> On Mon, Oct 28, 2024 at 2:41 PM Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> > On 10/28/24 11:34, Geert Uytterhoeven wrote:
> > > On Fri, Oct 25, 2024 at 5:40 PM Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> > >> On 10/22/24 14:36, Geert Uytterhoeven wrote:
> > >>> On Tue, Oct 8, 2024 at 11:14 AM Geert Uytterhoeven
> > >>> <geert+renesas@xxxxxxxxx> wrote:
> > >>>> When CONFIG_ENERGY_MODEL=y, an error is printed on RZ/G2E and R-Car E3:
> > >>>>
> > >>>> cpu cpu0: EM: invalid perf. state: -22
> > >>>>
> > >>>> This happens because the Operating Points Parameters tables do not list
> > >>>> voltages, as they are all identical. Previously, it was assumed they
> > >>>> were optional, and unused, when none of the CPU nodes is tied to a
> > >>>> regulator using the "cpu-supply" property. This assumption turned out
> > >>>> to be incorrect, causing the reported error message.
> > >>>>
> > >>>> This RFC patch series fixes this by adding the missing voltages.
> > >>>>
> > >>>> Note that the Energy Model calculates energy efficiency by dividing the
> > >>>> (estimated) CPU power consumption by CPU core clock frequency. When all
> > >>>> voltages have the same value, the former is proportional to clock
> > >>>> frequency, and energy efficiency becomes a constant. Hence all
> > >>>> operating points are considered to have the same efficiency, and the
> > >>>> Energy Model always picks the one with the highest clock rate (see also
> > >>>> [1]).
> > >>>>
> > >>>> Alternatively, the Energy Model could be changed to silently ignore OPP
> > >>>> tables with missing frequencies. IMHO this is not an unusual case.
> > >>>>
> > >>>> Which approach should be taken?
> > >>>> Thanks for your comments!
> > >>>
> > >>> Any comments from the Energy Model and PM people?
> > >>
> > >> My apologies for delay.
> > >>
> > >> So you had issue with bogus Voltage values and removed them.
> > >>
> > >> There is another way to setup EM properly, via DT:
> > >> "opp-microwatt" [1].
> > >>
> > >> That micro watt value won't confuse other subsystems, like
> > >> your regulator fwk. It will only be used by the EM fwk.
> > >>
> > >> This would be an alternative to your voltage values.
> > >> Sounds better to you?
> > >
> > > For opp-microwatt, I do need to know the actual power consumption
> > > of the core, right?
> >
> > Correct. You can try to derived that in a way you did and put below.
> > Although, Dhrystone is a synthetic micro-benchmark with small
> > impact to data caches, so it will not use much power.
>
> Do you have a suggestion for a better load test? stress-ng?
>
> > > Full system power consumption while running the in-kernel
> > > Dhrystones benchmark:
> > >
> > > 800 MHz: avg 4972,55 mW, stdef 20,474 mW
> > > 1000 MHz: avg 5025,93 mW, stdef 18,644 mW
> > > 1200 MHz: avg 5059,63 mW, stdef 15,425 mW
> >
> > Right. From those power values can be try to derive the
> > 'CPU only power' values - assuming only one core was
> > running the test.
> >
> > AFAIU you don't have proper DVFS due to missing voltage scaling.
>
> Indeed.
>
> > Therefore...
> > Out of that I got these CPU power values:
> > 800MHz -> 174mW
>
> => 217.5 µW/MHz
>
> > 1000MHz -> 212mW
>
> => 212 µW/MHz
>
> > 1200MHz -> 261mW
BTW, how did you get from my avg mW values above to your CPU power mW
values? I seem to be missing something...
>
> => 217.5 µW/MHz.
>
> So 1000 MHz seems to be the most power-efficient.
>
> > > The system also has test points across a 0.005 Ohm sense resistor in
> > > the DVFS power supply line, but no on-board measurement sensor (like
> > > the MAX9611 on Salvator-X(S)), so I haven't measured anything
> > > there yet.
>
> I'll try to do some measurements at these test points.
So I measured the voltage across the sense resistor, and used that to
calculate the actual power draw:
A. Idle (1 or 2 CPU cores online doesn't seem to matter):
- 765 mW @ 800 MHz,
- 786 mW @ 1000 MHz,
- 807 mW @ 1200 MHz.
B. Maximum seen during "stress-ng -c 10" with 1 CPU core online:
- 993 mW @ 800 MHz,
- 1055 mW @ 1000 MHz,
- 1096 mW @ 1200 MHz.
C. Maximum seen during "stress-ng -c 10" with 2 CPU cores online:
- 1179 mW @ 800 MHz,
- 1303 mW @ 1000 MHz,
- 1386 mW @ 1200 MHz.
As expected, the A-C increase is about the double of the A-B increase,
due to the use of 2 CPU cores.
Thanks again!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
