From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757233Ab3LERbI (ORCPT ); Thu, 5 Dec 2013 12:31:08 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:38968 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756809Ab3LERbG (ORCPT ); Thu, 5 Dec 2013 12:31:06 -0500 Date: Thu, 5 Dec 2013 09:31:02 -0800 From: "Paul E. McKenney" To: Dave Jones , Linux Kernel Subject: Re: lots of brief rcu stalls. Message-ID: <20131205173102.GS15492@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20131204232838.GA25592@redhat.com> <20131205001614.GI15492@linux.vnet.ibm.com> <20131205012206.GA31349@redhat.com> <20131205164912.GA1585@linux.vnet.ibm.com> <20131205171550.GA30002@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131205171550.GA30002@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13120517-9332-0000-0000-0000026443FD Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 05, 2013 at 12:15:50PM -0500, Dave Jones wrote: > On Thu, Dec 05, 2013 at 08:49:12AM -0800, Paul E. McKenney wrote: > > > But what workload are you running that causes this? The only way I > > can think of to make this happen requires that you have at least one > > CPU spending more than 21 seconds running continuously in kernel mode. > > Is that what you are doing, or have you come up with some other creative > > way for this to happen? In the latter case, I would really like to know > > about it in case it exposes yet another flaw in my RCU design. ;-) > > just the regular trinity runs, so it could be anything. > (Running a few instances of it, with a couple dozen child processes each to drive up the loadavg) Well, trinity has caused kernel-mode execution periods in excess of 21 seconds in the past, so I will assume that this is the cause until further notice. > if only I had a trace or something that I could start to guess at what was happening :) Maybe creating such a trace would expose additional bugs. ;-) Thanx, Paul