Re: Regression in 4.8 - CPU speed set very low

[Larry Finger]

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)

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)

> > > > 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.

Larry