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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 27 Sep 2016 03:48:51 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Doug Smythies <dsmythies@...us.net>,
        'Srinivas Pandruvada' <srinivas.pandruvada@...ux.intel.com>,
        "'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 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@...ux-1t8h:~/rtlwifi_new> sensors
coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +83.0°C  (high = +84.0°C, crit = +100.0°C)
Core 0:         +83.0°C  (high = +84.0°C, crit = +100.0°C)
Core 1:         +74.0°C  (high = +84.0°C, crit = +100.0°C)

After the fault occurs, I get

finger@...ux-1t8h:~/rtlwifi_new> sensors
coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +44.0°C  (high = +84.0°C, crit = +100.0°C)
Core 0:         +43.0°C  (high = +84.0°C, crit = +100.0°C)
Core 1:         +41.0°C  (high = +84.0°C, crit = +100.0°C)

>
>>>>
>>>> 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