[dat-discussions] [openib-general] [RFC] DAT2.0immediatedataproposal

[Caitlin Bestler]

Larsen, Roy K wrote:

>> 
>> Even on iWARP transports small send data can be in-lined, avoiding
>> the need for buffers to be registered. A special API where the
>> length of the "send buffer" is known in advance makes this even
>> easier. 
> 
> Ah, I wasn't aware iWARP could carry inline data.  I take it
> that's not possible on an iWARP RDMA write PDU however.
> 

On the wire the data is always "in-line", only an RDMA Read
Request references data that is not part of the message.
The iWARP protocols do not specify much about the local
interface. That role has been taken by the RDMAC verbs
and RNIC-PI so far. 

The standard functionality defined in the RDMAC verbs do not
mandate support for Inline Send work request. Neither do the
IBTA verbs. The option shows up in APIs, and in firmware,
because it is a valuable optimization that improves latency
in the Device/host exchange independent of the wire protocol.

In the vast majority of cases, the user verbs can implement 
inline sends very easily whenever the data is shorter than
the SGL would have been.

So in the sense that you can view the SQ itself as a "registered
buffer" then it is true. But there is no need for a *separate*
registered buffer.