[ofa-general] Getting Started with RDMA

[Dotan Barak]

Adrien Guillon wrote:
> On Tue, Jul 8, 2008 at 7:02 AM, Or Gerlitz <ogerlitz at voltaire.com 
> <mailto:ogerlitz at voltaire.com>> wrote:
>
>     Please note that you have to have a netdevice up and running for
>     the IP subnet addresses you would be using with the rdma-cm. In
>     the IB case, this means IPoIB and in the iWARP case, it means a
>     network device set by the iWARP HW provider, in the current
>     implementations, it means Gb Ethernet devices.
>
>     Or.
>
>
>
> If I run IPoIB, do the RDMA operations involve the kernel?  How high 
> is the cost of abstraction to use RMDA with IPoIB on infiniband?
No,  IPoIB doesn't use RDMA operations:
The classical IPoIB is being implemented using UD QP (which doesn't 
support RDMA)
The connected mode of IPoIB is being implemented using RC QP (which 
supports RDMA operations)
but RDMA is not being used in this mode as well.

Dotan