From: Eugene Leitl (eugene.leitl@lrz.uni-muenchen.de)
Date: Mon Jul 12 1999 - 21:26:26 MDT
Billy Brown writes:
> AFAIK, all Microsoft apps have been written as "asynchronous message-passing
> object soup" since sometime in the mid-90s. Also, with the right software
Hey, so they really call OS.send.message() every few 100 machine
instructions, or so, and context-switch every 1 us? Really? Mouse
handler an object, keyboard handler an object, peripheral storage
each an object, each widget an object, each Excel cell an object,
almost always sitting in a different node so they have to send
messages? We're really talking about Microsoft, Redmond, local
universe here, are we?
They can't do it simply because performance on current architectures
would suck monumentally. You would have to emulate things, and context
switches on current hardware/software architectures are just a tad too
expensive for that.
Multithreading!=asynchronous message passing on many tiny objects.
We're talking about several thousands primitive (few kBytes) objects
which send message packets which are routed by hardware directly --
while the originator code may or may not wait for the ack/result
to arrive. If this exists at all, it is academic curiousity at best
(Thinking Machines might qualify, though I really doubt they exploited
their options fully every time). You certainly can't program these
things in standard languages as C/C++ with any efficiency. And I would
just love to see a programmer who can handle concurrent nonlinear
control flow in a distributed kObject application. This can get
arbitrarily hairy.
There's a dearth of apps even for Beowulfs, and god knows how
coarse-grain these are. No sir, don't think so.
> you can run a large app over a distributed architecture like this without
> having to explicitly modularize it to fit the hardware's quirks (see
Sure you can. Put x86 opcode sofware emulation into every node,
equipartition the old-generation binary over the nodes and send
a message to the appropriate node whenever PC leaves your node's
address space slice. Redundant as hell (OS nanokernel+ x86
emulator in every node) and efficient as treacle since purely
sequential, especially considering that you can't do 4 kCPUs
PIII/550 way, and interpreting/compiling existing code into
SWAR *would* require true AI.
> http://research.microsoft.com/sn/Millennium/, and especialy
> http://research.microsoft.com/sn/Millennium/Coign.html, for example).
Better yet, the
system builds on the existing Windows operating system,
so today's software won't become obsolete and
programmers can write new software the same way they
do now, for one machine or many.
Right. And pilots will worry about pig collision avoidance issues.
Looks nice as a concept, but even if it works it is no panacea. Will
alleviate migration psychologically since suggesting you can run your
apps on the new platform even if in reality you can't.
> But that isn't especially relevant, anyway. I was talking about programming
> techniques for existing PC hardware. Obviously, radical changes in hardware
Of what possible relevance is existing PC hardware/programming
techniques to uploading? I am not sure we're talking in the same
language here.
> can require equally radical changes in programming methods.
And even worse: vice versa.
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