Messages in this thread | | | Subject | Re: Regression in 4.8 - CPU speed set very low | From | Larry Finger <> | Date | Mon, 26 Sep 2016 19:48:23 -0500 |
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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
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