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

[Arlin Davis]

Roland Dreier wrote:

>    
>Hmm.  Can you put a number on how much better RDMA write with
>immediate is on current HCA hardware?  How does using the underlying
>OpenIB verbs ability to post a list of work requests compare (ie
>posting an RDMA write followed by a send in one verbs call)?
>Maybe "post multiple" is a better direction for DAT.
>  
>
With post multiple, unlike immediate data, you don't have the ability to 
distinguish between a normal receive and a rdma write completion 
indication on the other end. This is the uniqueness of the service that 
cannot be provided by the post multiple. Yes, post multiple would be a 
nice option for DAT it is just a different service. It would also be 
required to conform to the semantics rules of the bundled operations so 
you could not do any optimization tricks under the covers with an IB 
rdma_write_immediate operation.

-arlin

> - R.
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