From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933179AbWFXBQa (ORCPT ); Fri, 23 Jun 2006 21:16:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933182AbWFXBQ3 (ORCPT ); Fri, 23 Jun 2006 21:16:29 -0400 Received: from mail29.syd.optusnet.com.au ([211.29.132.171]:6607 "EHLO mail29.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S933179AbWFXBQ3 (ORCPT ); Fri, 23 Jun 2006 21:16:29 -0400 From: Con Kolivas To: linux-kernel@vger.kernel.org Subject: Re: [PATCHSET] Announce: High-res timers, tickless/dyntick =?iso-8859-1?q?and=09dynamic_HZ?= -V4 Date: Sat, 24 Jun 2006 11:15:31 +1000 User-Agent: KMail/1.9.3 Cc: Robert Hancock , tglx@timesys.com, Ingo Molnar , Andrew Morton , Michal Piotrowski References: <449C8C7E.1040500@shaw.ca> <200606241109.56414.kernel@kolivas.org> In-Reply-To: <200606241109.56414.kernel@kolivas.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200606241115.32042.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 24 June 2006 11:09, Con Kolivas wrote: > On Saturday 24 June 2006 10:51, Robert Hancock wrote: > > Thomas Gleixner wrote: > > > On Thu, 2006-06-22 at 21:31 -0600, Robert Hancock wrote: > > >> Thomas Gleixner wrote: > > >>> An updated patchset is available from: > > >>> > > >>> http://www.tglx.de/projects/hrtimers/2.6.17/patch-2.6.17-hrt-dyntick4 > > >>>.p atch > > >> > > >> On my Compaq Presario X1050 laptop running Fedora Core 5 I get: > > >> > > >> Disabling NO_HZ and high resolution timers due to timer broadcasting > > >> > > >> Not sure exactly what this is indicating or what's triggered this, but > > >> I'm assuming the patch isn't doing much on this machine? > > > > > > The system is configured for SMP, but this is an UP machine and the > > > APIC is disabled in the BIOS. Linux uses then the PIT and an IPI > > > mechanism to broadcast timer events. We need to do the event > > > reprogramming per CPU, so we switch off in that situation. > > > > > > Solution: Either use an UP kernel, or enable Local APIC in the BIOS (is > > > not possible in most BIOSes), or add "lapic" to the kernel command > > > line. > > > > > > Also for an UP kernel adding "lapic" to the commandline is good, as the > > > APIC is faster accessible than the PIT. > > > > Tried that, still no dice: > > > > Kernel command line: ro root=/dev/VolGroup00/LogVol00 lapic > > Local APIC disabled by BIOS -- reenabling. > > Found and enabled local APIC! > > > > ... > > > > Disabling NO_HZ and high resolution timers due to timer broadcasting > > > > This isn't a viable solution for all machines anyway - some laptops > > disable the local APIC and the BIOS expects it to remain that way, and > > blows up if it gets turned on. > > One thing I did discover with my dynticks was that APIC on UP i386 was nigh > on broken for the most part. Virtually all BIOSs disable it and even if you > force enable it you may have to play with enable_timer_pin to get it to > work (sometimes 1, sometimes 0) and there was no pattern to when it would > be required since the BIOS manufacturer cared not. This is why for UP I > disabled APIC when dynticks was enabled, and would test for one online cpu > on SMP and do the same. This obviously isn't a solution when cpu hotplug is > enabled and only one cpu is online. That was enable_timer_pin_1 and disable_timer_pin_1 sorry. -- -ck