There is no doubt you will lose performance, but remember that shared memory is -only- used between procs on the same node. So the performance penalty for multi-node applications is considerably less.

Ultimately, the magnitude of the performance loss depends strongly on the design of the application (how much comm vs computation, etc.), how many nodes it runs across, the quality of the interconnect between those nodes, etc. etc.


On Aug 15, 2010, at 7:22 PM, 张晶 wrote:

 Hi Ralph,

I wonder if I disable the btl-sm component ,the performance of message passing will degrade.I need to test how much performance are lost. The code quality now is far from to be integrated into trunk,  I will try to clean up my code before sending these changes to you .

在 2010年8月13日 下午12:00,Ralph Castain <rhc@open-mpi.org>写道:
This sounds like excellent progress! Jeff and others know much more about MTT than I do, so I'll leave that question to them.

You have two approaches to the mmap issue. Easiest for now would be to simply disable the shared memory component - you can either turn it off at run-time with -mca btl ^sm, or you can direct that it not even be built with -enable-mca-no-build=btl-sm when configuring OMPI.

I would think your TCP comm would then allow the two procs sharing a host to communicate. Can you give that a try?

I'd be happy to begin reviewing the changes, and can help integrate them back into the OMPI trunk, when you feel ready.


On Aug 12, 2010, at 9:35 PM, 张晶 wrote:

Hi Ralph,Jeff and all

       It is a good news that I can almost run the openmpi on the vxworks ,but there are also still some bugs.The final test which has passed is:
      Rank 0 process  calls mpi_send running on the host 0,rank 1 process calls mpi_recv running on the host 1. It works well .For the absence of  the mmap in the vxworks  ,which is used in the btl sm component , it still fails running two processes in the same host.
      The difference between the vxworks and unix is the real trouble .For example pipe(),fork(),exec(),socketpair(),fcntl() ,sshd  and so no are not implemented in the vxworks .Replacing these lost with the correspond functions is the key work of the migration.After having a clear understanding of the function of rsh component ,I write a  simple daemon and client to launch the orted for the calling of the rlogin() in the user space of the vxworks complain. 
      I think there are still many test needed to be launching .Maybe I'd better to look into  MTT.

在 2010年7月8日 上午9:54,张晶 <iam.chilli@gmail.com>写道:
Thank you ,Squyres , it is really useful !

在 2010年7月7日 下午7:22,Jeff Squyres <jsquyres@cisco.com>写道:
On Jul 6, 2010, at 10:48 PM, 张晶 wrote:

> 1.If I write a rlogin component ,

Is the command line of rlogin that much different than that of rsh/ssh?  For example, can you just s/rsh/rlogin/ on the overall command line and have it just work?

If so, I suspect that tweaking the rsh plm might be far simpler than having your own component.

> can I just login in the node in the cluster and launch the process .  If it is ,what the role the odls plays ??

ODLS = ORTE Daemon Local launch Subsystem.

PLM = Process Lifecycle Management.

Meaning: the PLM is used to launch orteds (more on this below) across multiple nodes.  The ODLS is used to launch processes locally from the orted (e.g., via POSIX fork/exec).

> 2.what is orted? Should the orted exists in every node and functions as a node process launch proxy ?

Yes.  The orted = ORTE daemon.  It is almost always the first thing launched on each node and acts as a proxy for launching, killing, and monitoring the user's applications on each node.  It also does other control kinds of things, like relay stdout/stderr back up to the HNP (more below), etc.

> 3,what is hnp ? Is every job has only one hnp ,and when I use mpirun , the mpirun process is hnp ??

HNP = head node process, meaning mpirun (or actually, orterun -- mpirun is a symlink to orterun).  The HNP functions as an orted as well, so it can use the ODLS to launch processes locally, etc.

Ralph can provide more detail on all of the above, but these are the basics.

--
Jeff Squyres
jsquyres@cisco.com
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