Re: Regression in 4.8 - CPU speed set very low

[Larry Finger]

On 09/26/2016 08:30 PM, Srinivas Pandruvada wrote:
> On Mon, 2016-09-26 at 19:48 -0500, Larry Finger wrote:
> > On 09/26/2016 07:21 PM, Rafael J. Wysocki wrote:
> > > On Tue, Sep 27, 2016 at 1:53 AM, Larry Finger <Larry.Finger@lwfinge
> > > r.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@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.
> > 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
> Your effective freq is lower than 800MHz. One of the possible reason is
> thermal throttling.
>
> What distro you are using?

openSUSE Leap 42.1.

Larry