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

From: Qian Cai
Date: Thu Jun 24 2021 - 11:18:03 EST

On 6/24/2021 6:48 AM, Ionela Voinescu wrote:
> Not if the counters are implemented properly. The kernel considers that
> both reference and delivered performance counters should stop or reset
> during idle. The kernel would not account for idle itself.
> If the reference performance counter does not stop during idle, while
> the core performance counter (delivered) does stop, the behavior above
> should be seen very often.
> Qian, do you see these small delivered performance values often or
> seldom?

Ionela, so I managed to upgrade the kernel on the system to today's linux-next which suppose to include this series. The delivered perf is now 280. However, scaling_min_freq (200 MHz) is not equal to lowest_perf (100).

scaling_driver: acpi_cppc
scaling_governor: schedutil

Is that normal because lowest_nonlinear_perf is 200?

Also, on this pretty idle system, 158 of 160 CPUs are always running in max freq (280 MHz). The other 2 are running in 243 and 213 MHz according to scaling_cur_freq. Apparently, "schedutil" does not work proper on this system. I am going to try other governors to narrow down the issue a bit.

FYI, here is the acpi_cppc registers reading:

ref:160705801 del:449594095