On 02/21/2016 12:52 AM, Chen, Yu C wrote:

quoted

-----Original Message-----
From: Arto Jantunen [mailto:viiru@iki.fi]
Sent: Sunday, February 21, 2016 4:45 PM
To: Chen, Yu C
Cc: Doug Smythies; 'Rafael J. Wysocki'; 'Viresh Kumar'; linux-
pm@vger.kernel.org; 'Srinivas Pandruvada'
Subject: Re: PROBLEM: Cpufreq constantly keeps frequency at maximum on
4.5-rc4

"Chen, Yu C" [off-list ref] writes:

quoted

quoted

-----Original Message-----
From: linux-pm-owner@vger.kernel.org [mailto:linux-pm-
owner@vger.kernel.org] On Behalf Of Arto Jantunen
Sent: Sunday, February 21, 2016 1:11 AM
To: Doug Smythies
Cc: 'Rafael J. Wysocki'; 'Viresh Kumar'; linux-pm@vger.kernel.org;
'Srinivas Pandruvada'
Subject: Re: PROBLEM: Cpufreq constantly keeps frequency at maximum
on
4.5-rc4

"Doug Smythies" [off-list ref] writes:

quoted

On 2106.02.20 00:50 Arto Jantunen wrote:

quoted

I can force the frequency down manually with cpufreq-set, so the
problem doesn't seem to be with the actual frequency changing.

  cpufreq-set modifies the value of scaling_max_freq, it looks like
your system always demands for the max freq, can you provide:
grep . /sys/devices/system/cpu/intel_pstate/*perf_pct
under powersave and performance?

Powersave:
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:22

Performance:
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:100

Also, adding intel_pstate=no_hwp to the command line does not change the
result. Changing that to intel_pstate=disable does fix the problem, so the
bug seems to be somewhere in intel_pstate instead of cpufreq core.

You have Skylake, which is not compatible with legacy ACPI P states with 
_PSS tables, so not running without intel_pstate is not much use. It may 
be running at at low P-state by disabling.

Is Debian use default mode as performance? I think Ubuntu uses 
performance mode as default.
What is the output of
cat cpu*/cpufreq/scaling_governor

Thanks,
Srinivas

1.It would be nice if a git bisect is used to find the commit causing this problem.

2.
# cd /sys/kernel/debug/tracing/
# echo 1 > events/power/pstate_sample/enable
# echo 1 > events/power/cpu_frequency/enable
# cat trace