Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759067AbYFDKBP (ORCPT ); Wed, 4 Jun 2008 06:01:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753209AbYFDKA7 (ORCPT ); Wed, 4 Jun 2008 06:00:59 -0400 Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121]:50472 "EHLO cdptpa-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753193AbYFDKA6 (ORCPT ); Wed, 4 Jun 2008 06:00:58 -0400 Message-ID: <48466745.5050802@cfl.rr.com> Date: Wed, 04 Jun 2008 05:58:29 -0400 From: Mark Hounschell User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Nick Piggin CC: Peter Zijlstra , 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 , Max Krasnyansky , 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> <200806031603.40731.nickpiggin@yahoo.com.au> In-Reply-To: <200806031603.40731.nickpiggin@yahoo.com.au> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2289 Lines: 59 Nick Piggin wrote: > On Tuesday 03 June 2008 08:45, 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. > > How come it is an abonination? It is an easy way to do what it does, > and it's actually not a bad thing for some uses not to have to use > cpusets. > > Given that it's all __init code anyway, is there a real reason _to_ > remove it? IMHO, What is an abonination, is that cpusets are equired for this type of isolation to begin with, even on a 2 processor machine. I would like the option to stay and be extended like Max originally proposed. If cpusets/hotplug are configured isolation would be obtained using them. If not then isolcpus could be used to get the same isolation. From a user land point of view, I just want an easy way to fully isolate a particular cpu. Even a new syscall or extension to sched_setaffinity would make me happy. Cpusets and hotplug don't. Again this is just MHO. Regards Mark -- 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/