Newsgroups: comp.parallel.pvm,comp.edu
From: chris@cs.uwa.oz.au (chris mcdonald)
Subject: PVM in undergraduate teaching environments
Keywords: minimizing pvmd's
Organization: The University of Western Australia, Department of Computer Science
Date: 27 May 95 07:25:50 GMT
Message-ID: <chris.801559550@bison>

We would like to use PVM next semester (July) in our undergraduate
concurrency course of about 60+ students.
The students have access to a handful of workstations on the same IP subnet;
each host is host.equivalent and we have the ability to "register" these
students as users of our PVM environment.

Each student will be running about 20 (20 sec) pvm processes somewhere
on the VM, with each host having about 20-30 simultaneous logins.
Although we have not undertaken any experiments yet, the thought of
each student having (and leaving) a pvmd running on each host has us concerned.

We are considering the idea of a single (setuid-ed root) pvmd running on
each host that has a concept/understanding of users/uids.
We have seen that 18 bits are available in the task id's and are considering
employing 8 of these to carry user info (actually an index into a table of
pre-registered users).
Clearly, each pvmd would need (or need to support) separate queues for task
and message info, and each message would implicitly be carrying the user-id
in its sending task-id.

We feel we have an understanding of what changes this would require -
    a routine (on daemon startup) to read a valid user-list from disk,
    a routine (on client startup) to validate the current user,
    a setuid pvmd to spawn new tasks for registered users,
    modified library calls aware of the knowledge in task-ids,
    a modified pvm console to only list one's own tasks, ...

Has anyone seen or implemented a similar approach, or know of practical
strong reasons why the single pvmd approach is a bad idea in this setting
[the big bottleneck has us concerned too]?
Any info on alternative approaches?

Any help or comments welcomed. Thanks,

_______________________________________________________________________________
                       Chris McDonald     EMAIL:  chris@cs.uwa.edu.au
       Department of Computer Science       WWW:  http://www.cs.uwa.edu.au/
  The University of Western Australia     PHONE:  ((+61) 09) 380 2533
     Crawley, Western Australia, 6907       FAX:  ((+61) 09) 380 1089

