From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754052AbcIIRjd (ORCPT ); Fri, 9 Sep 2016 13:39:33 -0400 Received: from mail-oi0-f66.google.com ([209.85.218.66]:35787 "EHLO mail-oi0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752015AbcIIRjb (ORCPT ); Fri, 9 Sep 2016 13:39:31 -0400 From: Larry Finger Subject: Regression in 4.8 - CPU speed set very low To: LKML Message-ID: Date: Fri, 9 Sep 2016 12:39:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I have found a regression in kernel 4.8-rc2 that causes the speed of my laptop with an Intel(R) Core(TM) i7-4600M CPU @ 2.90GHz to suddenly have a maximum cpu frequency of ~400 MHz. Unfortunately, I do not know how to trigger this problem, thus a bisection is not possible. It usually happens under heavy load, such as a kernel build or the RPM build of VirtualBox, but it does not always fail with these loads. In my most recent failure, 'hwinfo --cpu' reports cpu MHz of 396.130 for #3. The bogomips value is 5787.73, and the cpu clock before the fault is 3437 MHz. Nothing is logged when this happens. If I were to get a patch that would show a backtrace when the maximum CPU frequency is changed, perhaps it would be possible to track this bug. Sorry that I can not be more specific. Larry