Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758493AbYFDQbP (ORCPT ); Wed, 4 Jun 2008 12:31:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753292AbYFDQa7 (ORCPT ); Wed, 4 Jun 2008 12:30:59 -0400 Received: from smtprelay01.ispgateway.de ([80.67.18.13]:48150 "EHLO smtprelay01.ispgateway.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752253AbYFDQa6 (ORCPT ); Wed, 4 Jun 2008 12:30:58 -0400 X-Greylist: delayed 742 seconds by postgrey-1.27 at vger.kernel.org; Wed, 04 Jun 2008 12:30:58 EDT From: Ingo Oeser To: Max Krasnyanskiy Subject: Re: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses) Date: Wed, 4 Jun 2008 18:18:27 +0200 User-Agent: KMail/1.9.9 Cc: Dimitri Sivanich , Peter Zijlstra , Paul Jackson , linux-kernel@vger.kernel.org, Con Kolivas , "Derek L. Fults" , devik , Dinakar Guniguntala , Emmanuel Pacaud , Frederik Deweerdt , Ingo Molnar , Matthew Dobson , Nick Piggin , rostedt@goodmis.org, Oleg Nesterov , "Paul E. McKenney" , Paul Menage , "Randy.Dunlap" , suresh.b.siddha@intel.com, Thomas Gleixner References: <20080601213019.14ea8ef8.pj@sgi.com> <4844BB41.7000605@qualcomm.com> <4845D825.6000403@qualcomm.com> In-Reply-To: <4845D825.6000403@qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200806041818.29709.ioe-lkml@rameria.de> X-Df-Sender: 849595 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1229 Lines: 34 Hi Max, On Wednesday 04 June 2008, Max Krasnyanskiy wrote: > btw Ingo, I just realized that maxcpu= option is exactly what you need. > Here is how you can use it. > Boot your system with maxcpus=1. That way the kernel will only bring up > processor 0. I'm assuming cpu0 is "good" otherwise your system is totally > busted :). Other cpus will stay off-line and will not be initialized. > Then once the system boots you can selectively bring "good" processors online > by doing > echo 1 > /sys/devices/system/cpu/cpuN/online > I just tested it on the Ubuntu Hardy standard kernel on an AMD DualCore. The /sys/devices/system/cpu/cpu1 entry doesn't show up. I can send you the dmesg/config in private, if you want. Did you test your suggestion? After our discussion, I tried to find the right spot to implement "disablecpus=" myself, but couldn't find the right position to hook it up. If your idea would work out, I would ACK it. Even in bold :-) Best Regards Ingo Oeser -- 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/