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SubjectRe: what's next for the linux kernel?
On Mon, 3 Oct 2005, Luke Kenneth Casson Leighton wrote:

> On Sun, Oct 02, 2005 at 05:05:42PM -0400, Rik van Riel wrote:
> > On Sun, 2 Oct 2005, Luke Kenneth Casson Leighton wrote:
> >
> > > and, what is the linux kernel?
> > >
> > > it's a daft, monolithic design that is suitable and faster on
> > > single-processor systems, and that design is going to look _really_
> > > outdated, really soon.
> >
> > Linux already has a number of scalable SMP synchronisation
> > mechanisms.
> ... and you are tied in to the decisions made by the linux kernel
> developers.
> whereas, if you allow something like a message-passing design (such as
> in the port of the linux kernel to l4), you have the option to try out
> different underlying structures - _without_ having to totally redesign
> the infrastructure.
> several people involved with the l4linux project have already done
> that: as i mentioned in the original post, there are about three or
> four different and separate l4 microkernels available for download
> (GPL) and one of them is ported to stacks of different architectures,
> and one of them is SMP capable and even includes a virtual machine
> environment.
> and they're only approx 30-40,000 lines each, btw.
> also, what about architectures that have features over-and-above SMP?
> in the original design of SMP it was assumed that if you have
> N processors that you have N-way access to memory.
> what if, therefore, someone comes up with an architecture that is
> better than or improves greatly upon SMP?

Like NUMA?

> they will need to make _significant_ inroads into the linux kernel
> code, whereas if, say, you oh i dunno provide hardware-accelerated
> parallel support for a nanokernel (such as l4) which just _happens_
> to be better than SMP then running anything which is l4 compliant gets
> the benefit.
> the reason i mention this is because arguments about saying "SMP is it,
> SMP is great, SMP is everything, we're improving our SMP design" don't
> entirely cut it, because SMP has limitations that don't scale properly
> to say 64 or 128 processors: sooner or later someone's going to come up
> with something better than SMP and all the efforts focussed on making
> SMP better in the linux kernel are going to look lame.
> l.
> p.s. yes i do know of a company that has improved on SMP.
> -

-Vadim Lobanov
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