linux-kernel - Re: Regression in 4.8 - CPU speed set very low

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Date:   Thu, 29 Sep 2016 08:56:16 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Larry Finger <Larry.Finger@...inger.net>,
        Zhang Rui <rui.zhang@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Doug Smythies <dsmythies@...us.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: Regression in 4.8 - CPU speed set very low

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.

Thanks,
Srinivas