From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S272228AbTG3TlO (ORCPT ); Wed, 30 Jul 2003 15:41:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S272234AbTG3TlO (ORCPT ); Wed, 30 Jul 2003 15:41:14 -0400 Received: from twilight.cs.hut.fi ([130.233.40.5]:54858 "EHLO twilight.cs.hut.fi") by vger.kernel.org with ESMTP id S272228AbTG3TlI (ORCPT ); Wed, 30 Jul 2003 15:41:08 -0400 Date: Wed, 30 Jul 2003 22:40:52 +0300 From: Ville Herva To: Mikael Pettersson Cc: ak@suse.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] NMI watchdog documentation Message-ID: <20030730194052.GS83336@niksula.cs.hut.fi> Mail-Followup-To: Ville Herva , Mikael Pettersson , ak@suse.de, linux-kernel@vger.kernel.org References: <200307301920.h6UJKXwC020610@harpo.it.uu.se> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200307301920.h6UJKXwC020610@harpo.it.uu.se> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 30, 2003 at 09:20:33PM +0200, you [Mikael Pettersson] wrote: > On Tue, 29 Jul 2003 20:53:19 +0300, Ville Herva wrote: > >On Tue, Jul 29, 2003 at 06:06:30PM +0200, you [Andi Kleen] wrote: > >> > Andi, you have the numbers mixed up. mode 1 is I/O-APIC, mode 2 is local APIC, > >> > and x86-64 defaults nmi_watchdog to I/O-APIC mode. > >> > Now, is it the I/O-APIC or local APIC watchdog that doesn't work in x86-64? > >> > >> Right, 1 and 2 need to be exchanged. Anyways local apic mode does not seem > >> to work, the kernel always reportss "NMI stuck" at bootup. > >> IO APIC mode for is default. > ... > >+For x86-64, the needed APIC is always compiled in, and the NMI watchdog is > >+always enabled with perfctr mode. Currently, mode=1 does not work on x86-64. > > Didn't Andi just say it's the other way around? nmi_watchdog=1 (I/O-APIC) > by default since nmi_watchdog=2 (local APIC) doesn't work. Ok, you got me confused (thankfully I didn't submit anything for inclusion yet. :) Initially, Andi said: http://marc.theaimsgroup.com/?l=linux-kernel&m=105941508314399&w=2 > x86-64 is the same, except APIC is always compiled in and the nmi watchdog > is always enabled with perfctr mode. mode=2 seems to also not work > correctly currently. > > However one caveat (even for i386): when you use perfctr mode 1 you lose > the first performance register which you may need for other things. To which I replied: http://marc.theaimsgroup.com/?l=linux-kernel&m=105942026020567&w=2 > So, is something like the following ok by you > > +For x86-64, the needed APIC is always compiled in, and the NMI watchdog is > +always enabled with perfctr mode. Currently, mode=2 does not work on x86-64. > + > +Using NMI watchdog (in mode=1) needs the first performance register, so you > +can't use it for other purposes (such as high precision performance > +profiling.) But you pointed out it was the other way around: http://marc.theaimsgroup.com/?l=linux-kernel&m=105947532631384&w=2 > Andi, you have the numbers mixed up. mode 1 is I/O-APIC, mode 2 is local > APIC, and x86-64 defaults nmi_watchdog to I/O-APIC mode. Now, is it the > I/O-APIC or local APIC watchdog that doesn't work in x86-64? And Andi agreed: http://marc.theaimsgroup.com/?l=linux-kernel&m=105949540722325&w=2 > Right, 1 and 2 need to be exchanged. Anyways local apic mode does not seem > to work, the kernel always reportss "NMI stuck" at bootup. IO APIC mode > for is default. So I proposed (blindly exchanging the numbers): http://marc.theaimsgroup.com/?l=linux-kernel&m=105950174531125&w=2 > +For x86-64, the needed APIC is always compiled in, and the NMI watchdog is > +always enabled with perfctr mode. Currently, mode=1 does not work on x86-64. > + > +Using NMI watchdog (in mode=2) needs the first performance register, so you > +can't use it for other purposes (such as high precision performance > +profiling.) So... Should it be something like: +For x86-64, the needed APIC is always compiled in, and the NMI watchdog is +always enabled with perctr mode. Currently, mode=2 (local APIC) does not +work on x86-64. IO APIC mode (mode=1) is the default. Using NMI watchdog +(mode=1) needs the first performance register, so you can't use it for +other purposes (such as high precision performance profiling.) (Is the last sentence only valid for x86-64?) -- v -- v@iki.fi