Re: Lets get this right (WAS RE:MOSIX and kernel mods)
Larry McVoy (lm@bitmover.com)
Sat, 06 Mar 1999 23:42:42 -0800
To: Richard Gooch <rgooch@atnf.csiro.au>
: If you hand me a network with computers and network orders of
: magnitude faster, do you think I'm going to keep doing the same thing?
: No way! I'm going to want render times under 30 milliseconds and
: datasets of a few hundred MBytes. I'm still going to care that
: grabbing a remote lock is going to be 4+ orders of magnitude more
: expensive than grabbing a local lock. So I'm still going to do SMP for
: the local nodes and MPI for the remote nodes, because I need to think
: about the two cases in a different way. I use locks because they're
: fast and there are benefits to using them and they're neater; but when
: locks would be slow, I do things a different way, and there the locks
: just get in the way: MPI is neater.
I'm really giving myself a bad rep here, because I have to keep agreeing
with Richard :-) But hey, when he's right, he's right, what can I do :-)
Anyway, to make his point even stronger, the message passing interfaces
like PVM and MPI can also be optimized for the local case, in fact, SGI
does that - they have MPI libraries that know when the "remote" node is
actually local and then just use shared memory for that message.
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