From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 7 Sep 2001 01:20:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 7 Sep 2001 01:20:28 -0400 Received: from maynard.mail.mindspring.net ([207.69.200.243]:36386 "EHLO maynard.mail.mindspring.net") by vger.kernel.org with ESMTP id ; Fri, 7 Sep 2001 01:20:17 -0400 Subject: Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches From: Robert Love To: Daniel Phillips Cc: Christoph Lameter , linux-kernel@vger.kernel.org In-Reply-To: <20010907051231Z16200-26183+114@humbolt.nl.linux.org> In-Reply-To: <999837964.865.3.camel@phantasy> <20010907051231Z16200-26183+114@humbolt.nl.linux.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Mailer: Evolution/0.13.99+cvs.2001.09.05.07.08 (Preview Release) Date: 07 Sep 2001 01:20:40 -0400 Message-Id: <999840042.1164.14.camel@phantasy> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2001-09-07 at 01:19, Daniel Phillips wrote: > On September 7, 2001 06:45 am, Robert Love wrote: > > On Fri, 2001-09-07 at 00:36, Christoph Lameter wrote: > > > Given the minimal nature of the patch I would suggest that it become part > > > of 2.4.10 or 11 > > > > Are you kidding? We will be lucky to see this in during 2.5. > > Its a pretty big change. It makes the Linux kernel preemptible. > > CONFIG_PREEMPT and... ? > > This is a fairly big move, one I don't think any of the major Unices have > > done. > > The other Unices are at least evenly split, or mostly preemptible. > Typically, a more complex strategy is used where spinlocks can sleep > after a few spins. This patch is very conservative in that regard, > it basically just uses the structure we already have, SMP spinlocks. I did not know other Unices were (in general) preemptible. Solaris is? The only one I thought was preemptible was Irix. Anyhow, you are right about the simplistic approach we take. There are a few alternatives: mixing mutexes and shorter locks, priority-bearing semaphores, changing the way the preemption count works, etc. > > The only reason the patch is not _huge_ is because the Linux > > kernel is already setup for concurrency of this nature -- it does SMP. > > > > I suggest you read > > http://www.linuxdevices.com/articles/AT4185744181.html > > http://www.linuxdevices.com/articles/AT5152980814.html > > http://kpreempt.sourceforge.net > > > > and my previous threads on this issue, for more informaiton. > > Hmm, how did you read those and come to such a different conclusion? What different conclusion? What are you even arguing with me about? Do you think I am against a preemptible kernel? I _posted_ the damn patch, of course I am not. I probably agree with whatever you are thinking. -- Robert M. Love rml at ufl.edu rml at tech9.net