Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance
From: Qian Cai <hidden>
Date: 2021-06-24 15:18:03
Also in:
linux-acpi, lkml
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: /sys/devices/system/cpu/cpu0/acpi_cppc/feedback_ctrs ref:160705801 del:449594095 /sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf 300 /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq 1000 /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf 200 /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_perf 100 /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq 2800 /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_perf 280 /sys/devices/system/cpu/cpu0/acpi_cppc/reference_perf 100 /sys/devices/system/cpu/cpu0/acpi_cppc/wraparound_time 18446744073709551615