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Subject: Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency
 invariance
To:     Ionela Voinescu <ionela.voinescu@arm.com>,
        Vincent Guittot <vincent.guittot@linaro.org>
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From:   Qian Cai <quic_qiancai@quicinc.com>
Message-ID: <81ea7ae0-54fd-85ba-b3de-a34520cb7f29@quicinc.com>
Date:   Thu, 24 Jun 2021 16:44:36 -0400
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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?

FYI, the latest data point it that on the new kernel, the delivered performance does match the cpufreq_cur_freq. IOW, feedback_ctrs works fine. Also, "powersave" governor could bring down the scaling_cur_freq to scaling_min_freq. Right now, looks like the puzzles on this particular system as mentioned in the previous post are,

1) lowest_freq/lowest_perf != scaling_min_freq
2) CPPC + schedutil is not able to scale down CPUs.