Help with LAM

Adam Lazur alazur at
Thu Jul 13 10:27:25 PDT 2000

Peter Jay Salzman (p at said:
> i found the homepage for LAM and noticed they have RPM's (yay!).  we have a
> choice of:
> lam-6.4a3-tcp.1.i386.rpm
> lam-6.4a3-sysv.1.i386.rpm
> lam-6.4a3-usysv.1.i386.rpm
> lam-6.4a3-1.src.rpm
> i'm sure we don't want the src rpm since we're happy with simply using
> supplied binaries.
> what are the differences between the tcp, sysv and usysv rpm's?   which one
> should we use?   i just started playing around with the cluster, so i'm a
> newbie.  any help would be appreciated.

[ Quoted from ]

2. What does tcp, sysv, and usysv mean?

LAM provides three client-to-client transport layers which implement the
request progression interface (RPI). The three client-to-client transports are: 

tcp	The tcp transport uses TCP sockets for all interprocess communication. 

usysv 	The usysv transport is multi-protocol. Processes on the same node
	communicate via SYSV shared memory and processes on different nodes
	communicate via TCP sockets. It uses spin-locks for shared memory
	synchronization as well as a SYSV semaphore or pthread mutex for
	synchronizing access to a per node global shared memory pool.  The
	spin-locks require that the architecture has strongly ordered writes
	and this transport is only supported on such platforms.  It should be
	relatively easy to modify this transport to work on systems with weakly
	ordered writes by adding memory barriers in appropriate places. 

sysv 	The sysv transport is the same as the usysv transport except that SYSV
	semaphores are used for message synchronization rather than spin-locks.
	On some uniprocessor systems (e.g. Linux) the blocking nature of
	semaphores can lead to better performance than when using spin-locks.
	The usysv transport should give the best performance on SMPs. 

[ End quoted material ]


[                  Adam Lazur <alazur at>                     ]
[      Paralogic Inc. - -      ]

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