Date: Thu, 26 Jan 2006 09:48:19 -0500 From: John Baldwin <jhb@freebsd.org> To: Robert Watson <rwatson@freebsd.org> Cc: Murray Stokely <murray@freebsd.org>, Ceri Davies <ceri@submonkey.net>, doc-committers@freebsd.org, cvs-all@freebsd.org, cvs-doc@freebsd.org Subject: Re: cvs commit: www/en/releases/6.1R todo.sgml Message-ID: <200601260948.21491.jhb@freebsd.org> In-Reply-To: <20060126122528.E16741@fledge.watson.org> References: <200601260957.k0Q9vCUn054132@repoman.freebsd.org> <20060126101706.GJ36965@submonkey.net> <20060126122528.E16741@fledge.watson.org>
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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. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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