Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755807AbYFBXE3 (ORCPT ); Mon, 2 Jun 2008 19:04:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753546AbYFBXEM (ORCPT ); Mon, 2 Jun 2008 19:04:12 -0400 Received: from wolverine02.qualcomm.com ([199.106.114.251]:10231 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755438AbYFBXEF (ORCPT ); Mon, 2 Jun 2008 19:04:05 -0400 X-IronPort-AV: E=McAfee;i="5200,2160,5308"; a="3449275" Message-ID: <48447C75.8040203@qualcomm.com> Date: Mon, 02 Jun 2008 16:04:21 -0700 From: Max Krasnyansky User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Peter Zijlstra CC: Ingo Oeser , Paul Jackson , linux-kernel@vger.kernel.org, Con Kolivas , "Derek L. Fults" , devik , Dimitri Sivanich , 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 Subject: Re: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses) References: <20080601213019.14ea8ef8.pj@sgi.com> <200806030035.58387.ioe-lkml@rameria.de> <1212446707.6269.26.camel@lappy.programming.kicks-ass.net> In-Reply-To: <1212446707.6269.26.camel@lappy.programming.kicks-ass.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1841 Lines: 44 Peter Zijlstra wrote: > On Tue, 2008-06-03 at 00:35 +0200, Ingo Oeser wrote: >> Hi Paul, >> >> in short: NAK! >> >> On Monday 02 June 2008, Paul Jackson wrote: >>> (Aside to the RealTime folks -- is there a 'realtime' >>> email list which I should include in this discussion?) >>> >>> The kernel has a "isolcpus=" kernel boot time parameter. This >>> parameter isolates CPUs from scheduler load balancing, minimizing the >>> impact of scheduler latencies on realtime tasks running on those CPUs. >> I used it to mask out a defect CPU on a 8-CPU node of a >> HPC-cluster at a customer site, until the $BIG_VENDOR >> sent a replacement. And to prove $BIG_VENDOR, that we actually >> have a problem on THAT CPU. >> >> So I would really like to keep this fault isolation capability. >> I made my customer happy with that. >> >> I wish Linux had more such "mask out bad hardware" features >> to faciliate fault isolation and boot and runtime. > > Yeah - except that its not meant to be used as such - it will still > brings the cpu up, and it is still usable for the OS. > > So sorry, your abuse doesn't make for a case to keep this abomination. Ingo, I just wanted to elaborate on what Peter is saying. That CPU will still have to be _booted_ properly. It may be used for hard- and soft- interrupt processing, workqueues (internal kernel queuing mechanism) and kernel timers. In your particular case you're much much much better off with doing echo 0 > /sys/devices/system/cpuN/online either during initrd stage or as a first init script. That way bad cpu will be _completely_ disabled. Max -- 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/