Re: Regression in 4.8 - CPU speed set very low

[Larry Finger]

On 09/29/2016 10:56 AM, Srinivas Pandruvada wrote:
> On Thu, 2016-09-29 at 14:19 +0200, Rafael J. Wysocki wrote:
>
> [...]
>
> > > 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. :)
> > It looks like in 4.8-rc we made a change that caused the "high" trip
> > point to
> > be acted on.
> This high trip point we don't expose in thermal subsystem (the thermal
>  zone dump didn't show this anywhere as a trip). This is exposed by
> core-dts driver only. This is the point BIOS is supposed to act, I
> guess that's why you are seeing 50% clock modulation.
>
>
> Are you running thermald
>
> What is?
> # ps -e | grep thermald
>
>
> > Srinivas, Rui, do you recall what that can be?
> >
> > One more question (I think I asked it previously): In the failing
> > case
> > (4.8-rc1 and later), when the frequency drops down to the 400 MHz,
> > does it
> > ever go back higher or is it stuck at that level forever?
> >
> > In any case, it may help to file a bug at bugzilla.kernel.org against
> > CPU/thermal or similar and let me know the bug number.  We'll need to
> > collect some tracepoint data to debug this and some place to put them
> > into for easy reference.
> Yes, this is good idea.

To complete the record in this thread, the problem also happened with kernel 
4.7, thus it is not a regression in 4.8-rcX. The full discussion is at 
https://bugzilla.kernel.org/show_bug.cgi?id=173361.

Larry