Subject: [[email-masked]: NeWS process mechanism]

From: [email-masked]
Date: Fri, 3 Apr 87 02:57:27 EST

Date: Thursday, 2 April 1987 09:40:13 EST
From: [email-masked]
To: [email-masked]
Subject: NeWS process mechanism

When NeWS was first announced, there were some complaints posted about its
lightweight process mechanism.  The NeWS server allows each application
program to be represented by one or more processes within the server.
Nonpreemptive scheduling is used, which means that a process which computes
for a long time without explicitly yielding the processor will cripple the
response time of other processes.  Furthermore, Sun apparently encourages
people to write "critical sections" (i.e. atomic action sequences for
modifying shared data structures) simply by not yielding the processor until
the critical section is complete.  Both of these decisions were criticized
as having the potential to create undesirable interactions (read "bugs")
between independently written applications.  On the other hand, the
decisions helped to reduce the cost of the multiple-process mechanism.

Now that NeWS has been out for a while, perhaps enough experience has been
gained to make some judgements about whether these complaints are valid
*in the context of real applications*.  I'm soliciting reports from people
who have written NeWS applications, or who have run collections of NeWS
applications simultaneously, on whether they have run into problems of this
flavor.  Both no-problem reports and horror stories would be welcome.

Please e-mail responses to me, if possible; I'll summarize to the net if
there is interest.

				tom lane
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