From owner-cvs-all@FreeBSD.ORG Thu Jan 26 14:55:29 2006 Return-Path: X-Original-To: cvs-all@FreeBSD.org Delivered-To: cvs-all@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6FCB316A420; Thu, 26 Jan 2006 14:55:29 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id B430843D45; Thu, 26 Jan 2006 14:55:28 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from [192.168.254.11] (junior.samsco.home [192.168.254.11]) (authenticated bits=0) by pooker.samsco.org (8.13.4/8.13.4) with ESMTP id k0QEtOwN038088; Thu, 26 Jan 2006 07:55:25 -0700 (MST) (envelope-from scottl@samsco.org) Message-ID: <43D8E2E5.5060309@samsco.org> Date: Thu, 26 Jan 2006 07:55:33 -0700 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.12) Gecko/20051230 X-Accept-Language: en-us, en MIME-Version: 1.0 To: John Baldwin References: <200601260957.k0Q9vCUn054132@repoman.freebsd.org> <20060126101706.GJ36965@submonkey.net> <20060126122528.E16741@fledge.watson.org> <200601260948.21491.jhb@freebsd.org> In-Reply-To: <200601260948.21491.jhb@freebsd.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-1.4 required=3.8 tests=ALL_TRUSTED autolearn=failed version=3.1.0 X-Spam-Checker-Version: SpamAssassin 3.1.0 (2005-09-13) on pooker.samsco.org Cc: Murray Stokely , cvs-doc@FreeBSD.org, cvs-all@FreeBSD.org, Robert Watson , doc-committers@FreeBSD.org, Ceri Davies Subject: Re: cvs commit: www/en/releases/6.1R todo.sgml X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Jan 2006 14:55:29 -0000 John Baldwin wrote: > On Thursday 26 January 2006 07:27, Robert Watson wrote: > >>On Thu, 26 Jan 2006, Ceri Davies wrote: >> >>>On Thu, Jan 26, 2006 at 09:57:12AM +0000, Murray Stokely wrote: >>> >>>>murray 2006-01-26 09:57:12 UTC >>>> >>>> FreeBSD doc repository >>>> >>>> Modified files: >>>> en/releases/6.1R todo.sgml >>>> Log: >>>> Add kbdmux and sysinstall smp kernel install items from the ideas page >>>> to the 6.1 Desired Features list. >>> >>>I think it's a little late to mess with sysinstall to that extent for >>>6.1. Sounds like the kind of thing that could sit in -CURRENT for months, >>>but hardly anyone would actually be using it. It seems that the main >>>problem with sysinstall is that hardly any of our developers use it. >>> >>>On to the question: how often does an SMP kernel fail to boot where a UP >>>one might work? I remember that this used to be a problem, but if it's >>>still "too often", can we have just the bits that probe for an mptable >>>(or however we determine that there is more that one processor) in the UP >>>kernel without suffering that instability? >>> >>>What I'm basically asking is how much of the SMP code is really required >>>just to detect MP hardware? >> >>SMP kernels now pretty much universally run on UP systems, thanks to work >>John did a couple of years ago. The problem has historically been a >>performance once: the overhead of all the atomic instructions to run an SMP >>kernel on a UP system is significant. We're working gradually to improve >>that, but it's still quite noticeable. There has been talk of run-time >>compiling/relinking to use different versions of mutexes (and all that), >>but no progress as far as I know. I can't speak to how much information >>the loader has/needs to decide if it should auto-load an SMP kernel. A >>simpler version of the world says that you have an SMP kernel in >>sysinstall, and based on it probing CPUs, it sets the default kernel in the >>install to GENERIC or SMP. > > > Yes, I would very much prefer that the install just use an SMP kernel. Note > that on all the non-i386 architectures we just have SMP on in GENERIC if it > is supported. > SMP kernels still do not universally work on all i386 machines. I know that Alpha and Sparc hardware was designed from the ground up to support SMP, instead of being a bolted on hack like with x86, but that doesn't change the facts of the situation. Despite your work, I don't think it will ever be safe to make SMP be the default on x86. Scott