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

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Message-ID: <003001d2186d$02c34820$0849d860$@net>
Date:   Mon, 26 Sep 2016 20:12:38 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Srinivas Pandruvada'" <srinivas.pandruvada@...ux.intel.com>,
        "'Larry Finger'" <Larry.Finger@...inger.net>,
        "'Rafael J. Wysocki'" <rafael@...nel.org>
Cc:     "'Rafael J. Wysocki'" <rjw@...ysocki.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 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.

> 
>>> 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%.

>>> 
>>> 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?