Problem with MLM - conflict with 'portmap'?

1998-08-11 07:48:09
Subject: Problem with MLM - conflict with 'portmap'?
From: Steven Casagrande <steve_casagrande AT BE.IBM DOT COM>
To: nv-l AT lists.tivoli DOT com
Date: Tue, 11 Aug 1998 11:48:09 +0000

We are using the Netview MLM on our system, and whenever we start up
midmand, it destroys NFS performance on the system.  We've traced it
to one possibility: a possible conflict between 'portmap' and
'midmand'.  Using 'lsof', we found portmap and midmand both using
UDP:*.*  (whatever port *that*  is...), and when this happens, the
biods (NFS client daemons) don't use any CPU, and NFS performance is
terrible (several seconds for a 'df', for example).  Killing midmand
clears up the problem.

I suspect that the UDP:*.*  port is being fought over by midmand and
portmap (which acts as a broker for rpc services, including NFS).
Then, when packets get grabbed by midmand, the portmap never sees
them, and we're in a timeout condition for the NFS application.  The
bad performance seems random (sometimes it's OK), which might indicate
that the midmand was off doing something else, and the portman had a
chance to get at the socket.

Has anyone else seen this problem?  Any ideas for a work-around?

FYI: AIX, mlm, RS/6k-380/192MB RAM/584MB Swap,
very lightly loaded (just us chickens!).

Many thanks,

Steve Casagrande
IBM Belgium
Steve_Casagrande AT be.ibm DOT com

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