cvs commit: www/en/releases/6.1R todo.sgml

[John Baldwin]

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 at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org