[openib-general] IB mcast question

[Steve Wise]

I added some debug printks in mthca_multicast_attach().

Roland, does this look ok to you? It seems correct to me:

# dmesg
mthca_multicast_attach qp_num 406 gid ff124001ffff0000:00000000000a0a0a lid c003
mthca_multicast_attach line 167 - found mgm, hash a20, prev ffffffff, index a20
mthca_multicast_attach line 197 - updated mgm gid: mgm gid ff124001ffff0000:00000000000a0a0a
mthca_multicast_attach line 219 - writing mgm: mgm->qp[0] 80000406 (BE)
mthca_multicast_attach qp_num 407 gid ff124001ffff0000:00000000000a0a0a lid c003
mthca_multicast_attach line 167 - found mgm, hash a20, prev ffffffff, index a20
mthca_multicast_attach line 197 - updated mgm gid: mgm gid ff124001ffff0000:00000000000a0a0a
mthca_multicast_attach line 219 - writing mgm: mgm->qp[1] 80000407 (BE)



On Mon, 2006-08-14 at 14:30 -0700, Sean Hefty wrote:
> Steve Wise wrote:
> > ib_multicast takes care of sending the join/leave info to the SA, right?
> > It keeps track of _when_ to leave, for instance.  So since opensm -is-
> > getting the join and setting up the group, and the mcast packet is being
> > passed to the first member who joined, then I don't think ib_multicast
> > can mess up the subsequent members, can it?  
> 
> It theory, it shouldn't mess up subsequent members.  While the first join is 
> active, subsequent join / leave requests to that same group should be queued. 
> After the first join completes, subsequent joins should get a copy of the 
> MCMemberRecord that was returned by the SA.
> 
> (This is a slight simplification, with the actual operation determined by the 
> type of join operation that occurs.  But for the RDMA CM, this is what should 
> happen.)
> 
> > I'm new to IB mcast, so I'm learning, but it seems like the mthca
> > firmware maybe isn't doing the right thing here.  
> 
> This was my suspicion, but I couldn't be certain.  It would help if anyone can 
> say that they've successfully tested this sort of multicast configuration.  I.e. 
> two QPs from the same HCA in the same group.
> 
> - SeanR