From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757173AbcH2Kr4 (ORCPT ); Mon, 29 Aug 2016 06:47:56 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:41472 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757152AbcH2Kry (ORCPT ); Mon, 29 Aug 2016 06:47:54 -0400 Date: Mon, 29 Aug 2016 12:45:18 +0200 (CEST) From: Thomas Gleixner To: Mac Lin cc: Vegard Nossum , John Stultz , LKML Subject: Re: Random abnormal high CPU sys usage related to timer In-Reply-To: Message-ID: References: User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 27 Aug 2016, Mac Lin wrote: > Hi Vegard, > Thanks for the prompt response. > The commit is introduced since 4.6, but the issue can be reproduced at > 3.10 (earliest I have ever test). And testing on buildroot+4.7 with > the commit reverted, the issue still happen. > > In fact, I did a test that ran a script that keep increase a counter > for 10 seconds on the same CPU. If I ran 2 of it, the number is half > of running 1. But if I ran it while the issue happened, the counter > reported is around the same value as the 1 process case. So I doubt > that it might be an issue of reported number. > > Is there other way to ensure the CPU is "really" doing something? Tracing will tell you exactly what's going on in the system. Thanks, tglx