Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161037AbXB0Iy0 (ORCPT ); Tue, 27 Feb 2007 03:54:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161062AbXB0Iy0 (ORCPT ); Tue, 27 Feb 2007 03:54:26 -0500 Received: from mail.gmx.net ([213.165.64.20]:36989 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1161037AbXB0IyY (ORCPT ); Tue, 27 Feb 2007 03:54:24 -0500 X-Provags-ID: V01U2FsdGVkX197CKBKNZt7gJ5PovfbOzfeS/SyCJCAVHambvF5j8 GBqw== Subject: Re: 2.6.21-rc1: known regressions (v2) (part 2) From: Mike Galbraith To: Ingo Molnar Cc: Michal Piotrowski , Thomas Gleixner , Adrian Bunk , Linus Torvalds , Andrew Morton , Linux Kernel Mailing List , "David P. Reed" , Ayaz Abdulla , jgarzik@pobox.com, netdev@vger.kernel.org, Albert Hopkins , Bob Tracy , Mark Brown , "Michael S. Tsirkin" In-Reply-To: <20070227083349.GB30376@elte.hu> References: <20070226220521.GB29575@stusta.de> <1172564491.3709.5.camel@chaos> <45E3ECF1.4040906@googlemail.com> <20070227083349.GB30376@elte.hu> Content-Type: text/plain; charset=iso-8859-2 Date: Tue, 27 Feb 2007 09:54:13 +0100 Message-Id: <1172566453.7009.28.camel@Homer.simpson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2 Content-Transfer-Encoding: 8bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2103 Lines: 51 On Tue, 2007-02-27 at 09:33 +0100, Ingo Molnar wrote: > * Michal Piotrowski wrote: > > > Thomas Gleixner napisa?(a): > > > Adrian, > > > > > > On Mon, 2007-02-26 at 23:05 +0100, Adrian Bunk wrote: > > >> Subject : kernel BUG at kernel/time/tick-sched.c:168 (CONFIG_NO_HZ) > > >> References : http://lkml.org/lkml/2007/2/16/346 > > >> Submitter : Michal Piotrowski > > >> Handled-By : Thomas Gleixner > > >> Status : problem is being debugged > > > > > > The BUG_ON() was replaced by a warning printk(). The BUG_ON() exposed a > > > problem with the SMT scheduler. See below. > > > > > >> Subject : BUG: soft lockup detected on CPU#0 > > >> NOHZ: local_softirq_pending 20 (SMT scheduler) > > >> References : http://lkml.org/lkml/2007/2/20/257 > > >> Submitter : Michal Piotrowski > > >> Handled-By : Thomas Gleixner > > >> Ingo Molnar > > >> Status : problem is being debugged > > > > > > Patch available, not confirmed yet. > > > > > > > I can confirm that the bug is fixed (over 20 hours of testing should > > be enough). > > thanks alot! I think this thing was a long-term performance/latency > regression in HT scheduling as well. Agreed. I was recently looking at that spot because I found that niced tasks were taking latency hits, and disabled it, which helped a bunch. I also can't understand why it would be OK to interleave a normal task with an RT task sometimes, but not others.. that's meaningless to the RT task. IMHO, SMT scheduling should be a buyer beware thing. Maximizing your core utilization comes at a price, but so does disabling it, so I think letting the user decide what he wants is the right thing to do. -Mike - 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/