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SubjectRe: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance
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On 6/25/2021 10:37 AM, Ionela Voinescu wrote:
> Quick questions for you:
>
> 1. When you say you tried a 5.4 kernel, did you try it with these
> patches backported? They also have some dependencies with the recent
> changes in the arch topology driver and cpufreq so they would not be
> straight forward to backport.
>
> If the 5.4 kernel you tried did not have these patches, it might be best
> to try next/master that has these patches, but with
> CONFIG_ACPI_CPPC_CPUFREQ_FIE=n, just to eliminate the possibility that
> an incorrect frequency scale factor here would affect utilization that
> would then affect the schedutil frequency selection. I would not expect
> this behavior even if the scale factor was wrong, but it would be good
> to rule out.
>
> 2. Is your platform booting with all CPUs? Are any hotplug operations
> done in your scenario?

Ionela, I found that set ACPI_PROCESSOR=y instead of ACPI_PROCESSOR=m will fix the previous mentioned issues here (any explanations of that?) even though the scaling down is not perfect. Now, we have the following on this idle system:

# cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_cur_freq | sort | uniq -c
79 1000000
1 1160000
73 1400000
1 2000000
4 2010000
1 2800000
1 860000

Even if I rerun a few times, there could still have a few CPUs running lower than lowest_perf (1GHz). Also, even though I set all CPUs to use "userspace" governor and set freq to the lowest. A few CPUs keep changing at will.

# cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_cur_freq | sort | uniq -c
156 1000000
3 2000000
1 760000

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