***SPAM*** Re: [ofa-general] Getting Started with RDMA

[Or Gerlitz]

Adrien Guillon wrote:
> How difficult is it in reality to use this library?  I assume that 
> this would give better performance than RDMA CM?  I also presume that 
> I can do RDMA operations with that, since Infiniband provides them in 
> the standard.
Among other knocks, if you choose to use libibcm then your addressing 
model should be built upon IB GIDs and you would have to emulate IB L2 
route lookup (IB SA queries) since there's no libibsa existing - wheres 
if you use librdmacm you can use IP addresses  in your addressing scheme 
and can issue a real IB route lookup. Needless to say that your code 
would work on all supported RDMA transports (currently IB and iWARP).

Both libibcm and librdmacm emulate/add nothing in the access to the data 
path, that is with both you create and use an (say) RC QP created by 
libibverbs and later work with the low level device specific (eg 
NetEffect, Mellanox, IBM, Chelsio, Qlogic, etc) user space library 
(through libibverbs proxy-ing the data calls) - so in that respect no 
performance difference is introduced by either of them.

Or.