Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762465AbXEJVz7 (ORCPT ); Thu, 10 May 2007 17:55:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755932AbXEJVzu (ORCPT ); Thu, 10 May 2007 17:55:50 -0400 Received: from www.osadl.org ([213.239.205.134]:43351 "EHLO mail.tglx.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755657AbXEJVzt (ORCPT ); Thu, 10 May 2007 17:55:49 -0400 Subject: Re: [BUG] local_softirq_pending storm From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Anant Nitya Cc: linux-kernel@vger.kernel.org In-Reply-To: References: <200705091942.22920.kernel@prachanda.hub> <1178728280.3042.504.camel@localhost.localdomain> Content-Type: text/plain Date: Thu, 10 May 2007 23:58:46 +0200 Message-Id: <1178834326.22481.18.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2287 Lines: 44 On Thu, 2007-05-10 at 17:23 +0530, Anant Nitya wrote: > On 5/9/07, Thomas Gleixner wrote: > > On Wed, 2007-05-09 at 19:42 +0530, Anant Nitya wrote: > > > Hi, > > > Ever since I upgrade to 2.6.21/.1, system log is filled with following > > > messages if I enable CONFIG_NO_HZ=y, going through archives it seems ingo > > > sometime back posted some patch and now it is upstream, but its not helping > > > here. If I disable NOHZ by kernel command line nohz=off this problem > > > disappears. This system is P4/2.40GHz/HT with SMP/SMT on in kernel config. > > > One more thing that I noticed is this problem only arises while using X or > > > network otherwise plain command line with no network access don't trigger > > > this with nohz=on. > > > > Is this independent of the load on the system ? i.e. : What happens if > > you only use the console and run a kernel compile with -j4 ? > Yep, it seems independent of load on the system, to test I compiled > kernel with make -j8 and to throw some more load same time I also used > amavisd to clean around 2000 of spam/virus infected mails and same > time was listening to few radio stream over net in console only login > mode. Even then there was not a single NOHZ: local_softirq_pending > message in log. Once kernel got compiled and amavisd finished its job > and load drops back to around 0.5/2.0 I started X and within few secs > log starts getting filled with local_softirq_pending messages, (sorry, > I didn't applied ratelimit patch since I wanted to test is it high > load on system that causes this or something else). It seems even > network operation is not causing this. It seems either X is doing > something terribly wrong or kernel is getting hosed by X. > If some more information is needed please feel free to ask Ok, that's consistent with earlier reports. The problem surfaces when one of the SMT-"cpus" goes idle. The problem goes away when you disable hyperthreading. When you apply the ratelimit patch, does the softlockup problem persist ? tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/