Where can I find out more on how to do this, i.e. use opensm to create
mc groups at startup?
Quoting Ira Weiny <[email protected]>:
On Mon, 21 Nov 2011 09:05:22 -0800
"Hefty, Sean" <[email protected]> wrote:
> From what I understand, and I may not understand correctly, to
> perform IB Multicast, betweeen two nodes, I need to swap addresses and
> remote keys for the two nodes. In the examples I have seen this has
You only need to do this for unicast UD. Multicast doesn't require
exchanging addresses and qkeys, but see below.
> been done via RDMA CM directly between the two nodes. Does it matter
> how this information is exchanged? In my application I will have
For multicast, you need to 1. have the SA create the multicast
group and 2. join the group. To create the group, you need to
either have the SA automatically create the group (if this is
possible) or create it dynamically. To create the group
dynamically from user space, you should use the rdma_cm or ib_umad
interfaces. The rdma_cm is easier.
FWIW, OpenSM (current master branch) now has the ability to create
multicast groups at startup, so 1 is possible.
See: http://www.spinics.net/lists/linux-rdma/msg10021.html
Ira
To join the group, you need to let the SA know that the node should
receive multicast traffic, so that it can program the switches.
This is done through the rdma_cm (easy way) or using ib_umad (hard
way that gets harder if you want to support multiple applications
joining the same group from the same system).
> several nodes multicasting to several other nodes and I want to manage
> the connections from a independent application. What I would like to
> do is write this application, server, etc. so that each node would
> request connection with another node and then be provied with the
> information it needs to multicast. For example... Node 1 would
> request a connection (from the server app) Node 2 and Node 2 would
> request a connection (again, from the server app) to Node 1. The
> Server app would provide Node 2's "credentials" to Node 1 and likewise
> to Node 2. Is this even possible?
The SA basically does the work that you're describing for your
server app. Node 1 can ask the SA to create a multicast group.
Node 2 can ask to join that group. Somehow node 2 needs to know
what group node 1 created.
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Ira Weiny
Member of Technical Staff
Lawrence Livermore National Lab
925-423-8008
[email protected]
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