Re: Regression in 4.8 - CPU speed set very low

From	Larry Finger <Larry.Finger@lwfinger.net>
Newsgroups	linux.kernel
Subject	Re: Regression in 4.8 - CPU speed set very low
Date	2016-09-27 02:50 +0200
Message-ID	<slOKR-2t3-13@gated-at.bofh.it> (permalink)
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On 09/26/2016 07:21 PM, Rafael J. Wysocki wrote:
> On Tue, Sep 27, 2016 at 1:53 AM, Larry Finger <Larry.Finger@lwfinger.net> wrote:
>> On 09/26/2016 05:16 PM, Rafael J. Wysocki wrote:
>>>
>>> On Tue, Sep 27, 2016 at 12:09 AM, Larry Finger
>>
>> <Larry.Finger@lwfinger.net> wrote:
>>>
>>>
>>> Maybe it's better to try diagnose the problem instead of spending more
>>> time on bisection.
>>
>>
>> In my original post, I asked for such help, but nothing until today. I had
>> no idea what to check, but now I have a better idea.
>>
>>> I'd like to know whether or not 4.7 was definitely good, though.
>>
>>
>> I never saw this problem with 4.7, but given the difficulty in triggering
>> the problem, my tests may not have been definitive.
>>>
>>>
>>>> If it is one of them, it may be a while before I dare call this one
>>>> "good".
>>>> In one respect, that is good as I will be traveling tomorrow and
>>>> Wednesday.
>>>
>>>
>>> What does "cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver" say?
>>
>>
>> intel_pstate
>
> You probably don't need to worry about all of the cpufreq changes in
> 4.8-rc, then.  Only a few of them affect intel_pstate and I don't see
> how any of them may lead to the observed symptoms.
>
> First off, if you have a reproducer, please run it on 4.7 and see if
> you can trigger the issue in there.

I'm running 4.8-rc7 at the moment hoping to trigger the problem and get the data 
requested by Srinivas. Once I get that, I will try 4.7 again.
>
> Second, it would be good to have a look at the output from the
> cpu_frequency and pstate_sample tracepoints around when the issue
> triggers.  The pstate_sample one would be more interesting.
>
> But for both we need a reproducer anyway.

I do not have a reliable reproducer. The condition has always happened when 
running a high-compute job such as a 'make -j8' on the kernel, or building the 
RPM for openSUSE's implementation of VirtualBox. The latter is what I'm using 
for most of my testing.

> It also would be good to rule out the thermal throttling (as per the
> Srinivas' comments).
>
> For now, please tell me what's in
> /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq

800000

Larry

Thread

Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-24 04:50 +0200
  Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-09-26 13:40 +0200
    Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-26 18:20 +0200
      Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-09-26 23:10 +0200
        Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-26 23:30 +0200
          Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rafael@kernel.org> - 2016-09-26 23:40 +0200
            Re: Regression in 4.8 - CPU speed set very low Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> - 2016-09-26 23:50 +0200
              Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-27 00:20 +0200
            Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-27 00:20 +0200
              Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rafael@kernel.org> - 2016-09-27 00:20 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-27 02:00 +0200
                Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rafael@kernel.org> - 2016-09-27 02:30 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-27 02:50 +0200
                Re: Regression in 4.8 - CPU speed set very low Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> - 2016-09-27 03:40 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-27 05:00 +0200
                RE: Regression in 4.8 - CPU speed set very low "Doug Smythies" <dsmythies@telus.net> - 2016-09-27 05:20 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-27 10:50 +0200
                Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rafael@kernel.org> - 2016-09-27 13:50 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-29 04:30 +0200
                Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-09-29 14:20 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-29 17:10 +0200
                Re: Regression in 4.8 - CPU speed set very low Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> - 2016-09-29 18:00 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-29 18:30 +0200
                Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-09-29 22:50 +0200
                Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-10-01 00:00 +0200
          Re: Regression in 4.8 - CPU speed set very low lsorense@csclub.uwaterloo.ca (Lennart Sorensen) - 2016-09-27 17:00 +0200
            Re: Regression in 4.8 - CPU speed set very low Larry Finger <Larry.Finger@lwfinger.net> - 2016-09-29 04:30 +0200
              Re: Regression in 4.8 - CPU speed set very low lsorense@csclub.uwaterloo.ca (Lennart Sorensen) - 2016-09-29 16:20 +0200
        Re: Regression in 4.8 - CPU speed set very low Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> - 2016-09-26 23:30 +0200
          Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rafael@kernel.org> - 2016-09-26 23:40 +0200
            Re: Regression in 4.8 - CPU speed set very low Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> - 2016-09-26 23:50 +0200
              Re: Regression in 4.8 - CPU speed set very low "Rafael J. Wysocki" <rafael@kernel.org> - 2016-09-26 23:50 +0200

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