Newsgroups: comp.parallel.pvm
From: crispin@csd.uwo.ca (Crispin Cowan)
Subject: Re: PVM on Windows PCs?
Organization: Department of Computer Science, University of Western Ontario, London, Ontario, Canada
Date: 26 Aug 1994 19:40:05 GMT
Message-ID: <33lgel$3no@falcon.ccs.uwo.ca>

In article <33kjvm$pjc@cantaloupe.srv.cs.cmu.edu>,
Peter A Dinda <pdinda@cs.cmu.edu> wrote:
>In article <33jadr$gbo@falcon.ccs.uwo.ca>,
>Crispin Cowan <crispin@csd.uwo.ca> wrote:
>>	-it will suck (lack of true multitasking)
>I'm not sure how you define "suck."  Depending on how it was
It will fail to get maximal usage from the CPU, fail to give timely
response to the console user, or both, because of the lack of
pre-emptive sheduling.

>scheduling.  At the lowest level, pseudo-virtual machines are 
>preemptively scheduled.  These include DOS VMs that can run DPMI
News to me.  So you can get pre-emptively scheduled tasks under Windows
by calling them "virtual machines"?  What does "virtual machine" mean
in this context, how many can we have, and can we get pvm_spawn to
create a new one at will?

>>	-it will be unsafe (lack of inter-process protection)
>"lack" is the wrong word.  "weak" is more accurate.
What's the difference?

>>	-it will be a lot of work (to cobble together compatible
>>	 interfaces for signals, rsh, etc.)
>This has been done for other platforms:  Paragon, T3D, etc.
That's because the Paragon and T3D environments are what PVM is trying
to emulate in the first place.  Thus the "emulation" required to map
PVM system calls into Paragon or T3D calls amounts to changing the
order of the arguments and the name of the call.  BFD.

>>	-it will have portability problems (if compromises are made to
>>	 help with the previous points, such as mandating calls to
>>	 yield--ick)
>Again, this is true for PVM running on workstations.  It's certainly
>not the case for PVM running on a Paragon, T3D or under OS/2.  
As I said above, the issues are trivial for the Paragon and the T3D.
OS/2 actually resembles an operating system, and so while the issues
are non-trivial, they are managable.  To wit, OS/2 has:
	-pre-emptive multitasking
	-built in networking

Crispin
-----
Crispin Cowan, CS PhD student, searching for a research position
University of Western Ontario
Phyz-mail:  Middlesex College, MC28-C, London, Ontario, N6A 5B7
E-mail:     crispin@csd.uwo.ca          Voice:  519-661-3342
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