Re: Regression in 4.8 - CPU speed set very low

From: Rafael J. Wysocki
Date: Mon Sep 26 2016 - 20:21:48 EST

On Tue, Sep 27, 2016 at 1:53 AM, Larry Finger <Larry.Finger@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> 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.

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.

It also would be good to rule out the thermal throttling (as per the
Srinivas' comments).

For now, please tell me what's in