Re: Regression in 4.8 - CPU speed set very low

[Larry Finger]

On 09/27/2016 06:46 AM, Rafael J. Wysocki wrote:
> On Tue, Sep 27, 2016 at 10:48 AM, Larry Finger
> <Larry.Finger@xxxxxxxxxxxx> wrote:
> > On 09/26/2016 10:12 PM, Doug Smythies wrote:
> > > On 2016.09.26 18:31 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 wrote:
> > > > > > 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.
> > >
> > >
> > > Run some CPU stressor and get all your CPU's going at 100% load.
> > > And watch your core temperatures while you do so.
> >
> >
> > for i in 1 2 3 4; do while : ; do : ; done & done
> >
> > triggered the fault in a few minutes.
> > > > > > It also would be good to rule out the thermal throttling (as per
> > > > > > the Srinivas' comments).
> > >
> > >
> > > It is almost certainly thermal throttling, or similar causing
> > > Clock modulation, of it seems 50%.
> >
> >
> > While the infinite loops were running, the temps were:
> >
> > finger@linux-1t8h:~/rtlwifi_new> sensors
> > coretemp-isa-0000
> > Adapter: ISA adapter
> > Physical id 0:  +83.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
> > Core 0:         +83.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
> > Core 1:         +74.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
>
> It looks like the trip point (high) temperature was exceeded causing
> thermal throttling to kick in.
>
> > After the fault occurs, I get
> >
> > finger@linux-1t8h:~/rtlwifi_new> sensors
> > coretemp-isa-0000
> > Adapter: ISA adapter
> > Physical id 0:  +44.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
> > Core 0:         +43.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
> > Core 1:         +41.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
>
> So after that it stays at 400 MHz forever, right?
>
> > > > > > 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?
> > >
> > >
> > > And what make and model of LapTop?
> >
> >
> > Toshiba Tecra A50-A with CPU Model: 6.60.3 "Intel(R) Core(TM) i7-4600M CPU @
> > 2.90GHz. That is a dual-core unit with hyperthreading.
> >
> > @Rafael: As I write this, the system has been running the infinite loop test
> > for almost 5 hours with kernel 4.7. I will leave that running while I'm
> > gone, but I am certain that it is OK.
>
> OK, and what temperatures do you see while doing this?

finger@linux-1t8h:~/linux-2.6> sensors
coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +90.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
Core 0:         +90.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)
Core 1:         +78.0ÂC  (high = +84.0ÂC, crit = +100.0ÂC)

Once again, the CPU temp is greater than the "high" value; however, the clock 
rate continues to hold near 3600 MHz.

My laptop was inadvertently put to sleep while I was gone. I forgot to leave a 
note for my wife and she quieted the noisy cpu fan. :)

Larry