From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751200AbWGWMlp (ORCPT ); Sun, 23 Jul 2006 08:41:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751201AbWGWMlp (ORCPT ); Sun, 23 Jul 2006 08:41:45 -0400 Received: from smtp.osdl.org ([65.172.181.4]:61382 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751200AbWGWMlo (ORCPT ); Sun, 23 Jul 2006 08:41:44 -0400 Date: Sun, 23 Jul 2006 05:37:55 -0700 From: Andrew Morton To: Matthias Urlichs Cc: linux-kernel@vger.kernel.org, johnstul@us.ibm.com, torvalds@osdl.org, bunk@stusta.de, lethal@linux-sh.org, hirofumi@mail.parknet.co.jp Subject: Re: REGRESSION: the new i386 timer code fails to sync CPUs Message-Id: <20060723053755.0aaf9ce0.akpm@osdl.org> In-Reply-To: <20060723120829.GA7776@kiste.smurf.noris.de> References: <20060722233638.GC27566@kiste.smurf.noris.de> <20060722173649.952f909f.akpm@osdl.org> <20060723081604.GD27566@kiste.smurf.noris.de> <20060723044637.3857d428.akpm@osdl.org> <20060723120829.GA7776@kiste.smurf.noris.de> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.19; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 23 Jul 2006 14:08:29 +0200 Matthias Urlichs wrote: > Hi, > > Andrew Morton: > > - CPU0 and CPU1 share a TSC and CPU2 and CPU3 share another TSC. > > > That mmakes sense, since they're one dual-core Xeon each. OK. > > - Earlier kernels didn't use the TSC as a time source whereas this one > > does, hence the problems which you're observing. > > > Correct; see below. > > > I assume that booting with clock=pit or clock=pmtmr fixes it? > > > Testing... yes, both. > > > It would be useful to check your 2.6.17 boot logs, see if we can work out > > what 2.6.17 was using for a clock source. > > > That's easy: > > 2.6.17 -Using pmtmr for high-res timesource > 2.6.18git +Time: tsc clocksource has been installed. > > I missed those two lines, as in the boot logs they're not really > adjacent, so they got lost in the jumble of other differences. OK, thanks. Marking the TSC as bad in this case is simple to do - let us let John work out the best way. We must have lost a TSC sanity check somewhere along the way. I wonder what it was? > Interestingly, CPU0/1 gets 6000 bogomips while CPU2/3 only reaches 5600 ..? > (That happens with both kernels.) I do wonder why, and whether this has any > bearing on the current problem. I wouldn't expect it to matter, unless the TSCs are running at different speeds or something. Also the sched-domain migration costs are grossly different between the two kernels. Maybe we changed the migration-cost-estimation code; I forget. I'll see if we can get an expert opinion on the write_tsc() failure.