Newsgroups: comp.parallel.pvm
From: wjiang@thud.cs.utk.edu (weicheng jiang   )
Subject: Re: Message length limit on SUNMP?
Organization: Computer Science Dept, University of Tennessee, Knoxville
Date: 14 Sep 1994 18:34:37 GMT
Message-ID: <357fntINNohn@CS.UTK.EDU>

In article <34p768$e3c@beta.qmw.ac.uk>, j.p.woodcock@qmw.ac.uk (Jon Woodcock) writes:
|> Am I correct in thinking that there is a message length limit for the SUNMP
|> port of PVM3.3.3 not present in the SUN4 and SUN4SOL2 ports?
|> I'm running on a twin processor sun sparc20 (under unpatched Solaris 2.3).
|> The fault seems to occur when a message over ~1M is sent - there is no
|> complaint when the buffer is being packed but when it is sent the sending 
|> program locks up and eats processor time. This doesn't occur on the other 
|> Sun architectures I use.
|> 

The Readme.mp file says:

    2. The buffer size used by PVM, SHMBUFSIZE, is defined in
pvm3/src/pvmshmem.h, with a default of 1MBytes. Your message must fit
in the buffer. If your program uses large messages, this parameter MUST
be increased accordingly. Note that the default system limit on shared-
memory segment size (1 MB on Sun's) may have to be raised as well.
A large number of small messages can also fill up the buffer if they
are not received in time, and the performance degrades considerably
when this happens.

This may change in the future, but for the time being you'll have to put
up with this for a while.

Hope this helps,
  Weicheng Jiang


