From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933931AbcI2PJ2 (ORCPT ); Thu, 29 Sep 2016 11:09:28 -0400 Received: from mail-oi0-f51.google.com ([209.85.218.51]:35932 "EHLO mail-oi0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932897AbcI2PJ1 (ORCPT ); Thu, 29 Sep 2016 11:09:27 -0400 Subject: Re: Regression in 4.8 - CPU speed set very low To: "Rafael J. Wysocki" , Srinivas Pandruvada , Zhang Rui References: <5271ed6f-5798-e930-d7fd-17fe6bb7ea96@lwfinger.net> <16590757.26uEfRfeet@vostro.rjw.lan> Cc: "Rafael J. Wysocki" , Doug Smythies , LKML , Linux PM list From: Larry Finger Message-ID: <940c2e2f-24c8-b2aa-9c9c-e24f0eae1b77@lwfinger.net> Date: Thu, 29 Sep 2016 10:09:24 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <16590757.26uEfRfeet@vostro.rjw.lan> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/29/2016 07:19 AM, Rafael J. Wysocki wrote: > On Wednesday, September 28, 2016 09:22:59 PM Larry Finger wrote: >> On 09/27/2016 06:46 AM, Rafael J. Wysocki wrote: >>> On Tue, Sep 27, 2016 at 10:48 AM, Larry Finger >>> wrote: >>>> 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: +83.0°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) >>> >>> It looks like the trip point (high) temperature was exceeded causing >>> thermal throttling to kick in. >>> >>>> After the fault occurs, I get >>>> >>>> finger@linux-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) >>> >>> So after that it stays at 400 MHz forever, right? >>> >>>>>>>> >>>>>>>> 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. >>> >>> OK, and what temperatures do you see while doing this? >> >> finger@linux-1t8h:~/linux-2.6> sensors >> coretemp-isa-0000 >> Adapter: ISA adapter >> Physical id 0: +90.0°C (high = +84.0°C, crit = +100.0°C) >> Core 0: +90.0°C (high = +84.0°C, crit = +100.0°C) >> Core 1: +78.0°C (high = +84.0°C, crit = +100.0°C) >> >> Once again, the CPU temp is greater than the "high" value; however, the clock >> rate continues to hold near 3600 MHz. >> >> 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. > > 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. Sorry if I missed that earlier question. The CPU is stuck at that lower frequency until I reboot. Bug report at https://bugzilla.kernel.org/show_bug.cgi?id=173361. I tried to cover the main points of the discussion. Please add the ones that I missed. Larry