Re: Linux/Pro -- clusters

Donald Becker
2001-12-04T02:04:35Z

On Mon, 3 Dec 2001, Davide Libenzi wrote:

> On Mon, 3 Dec 2001, Donald Becker wrote:
> > of the change. We won't know for years if redesigning the kernel for
> > large scale SMP system is useful
> > - does it actually work,
> > - will big SMP machines be common, or even exist?
> > - will big SMP machines have the characteristics we predict
> > let alone worth the costs such as
> > - UP performance hit
> > - complexity increase slows other improvements
> > - difficult performance tuning
...
> No, I do not believe in 128 single CPU SMP machines but, if I've to watch
> inside my pretty dirty crystal ball, I see multi-core CPUs as a technology
> response to SMP request.
> Yes, because after the 1st theorem of "work" there's the 1st lemma of
> technology that states that "technology will always follow the
> market request".

You haven't addressed the points above.
We haven't established that the market will request substantial numbers
of 128-way SMPs. Even if they do request single-address-space
multiprocessors, it's very likely that the result will be some form of cc-numa
where the structure will strongly influence the OS to treat the machine
as something besides a SMP.

To bring this branch back on point: we should distinguish between
design for an arbitrary and unpredictable goal (e.g. 128 way SMP)
vs. putting some design into things that we are supposed to already
understand
a SCSI device layer that isn't three half-finished clean-ups
a VFS layer that doesn't require the kernel to know a priori all of
the filesystem types that might be loaded

Donald Becker becker@scyld.com
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Second Generation Beowulf Clusters
Annapolis MD 21403 410-990-9993