Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance

[Vincent Guittot]

On Thu, 24 Jun 2021 at 04:54, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>
> On 23-06-21, 08:57, Qian Cai wrote:
> > Viresh, I am afraid I don't feel comfortable yet. I have a few new tests in
> > development, and will provide an update once ready.
>
> Oh sure, np.
>
> > Also, I noticed the delivered perf is even smaller than lowest_perf (100).
>
> > # cat /sys/devices/system/cpu/cpu8/acpi_cppc/feedback_ctrs
> >  ref:103377547901 del:54540736873
> > # cat /sys/devices/system/cpu/cpu8/acpi_cppc/feedback_ctrs
> >  ref:103379170101 del:54541599117
> >
> > 100 * (54541599117 - 54540736873) / (103379170101 - 103377547901) = 53

I'm not sure that I understand your point. The formula above says that
cpu8 run @ 53% of nominal performance

> >
> > My understanding is that the delivered perf should fail into the range between
> > lowest_perf and highest_perf. Is that assumption correct? This happens on
> > 5.4-based kernel, so I am in process running your series on that system to see
> > if there is any differences. In any case, if it is a bug it is pre-existing,
> > but I'd like to understand a bit better in that front first.
>
> Vincent:
>
> Can that happen because of CPU idle ?
>
> --
> viresh