Re: CQEs in unreliable connection

[Dotan Barak <dotanba-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Anuj.

On 28/11/2013 14:24, Anuj Kalia wrote:
> Hi.
>
> I had 2 questions related to RDMA operations (reads and writes) over
> unreliable connections:
>
> 1. Are WQEs issued over an unreliable connection supposed to generate
> CQEs? The Infiniband spec says that such WQEs may not generate an
> 'ACK'. I'm confused if ACK refers to CQE.
ACK is an acknowledgment that was sent over the wire that the message 
was received by the remote side.
CQE is a mechanism to indicate that a Work Request isn't outstanding 
anymore.

In RC QP, a CQE with successful status of a Send Request means that an 
ACK was received by the sender.
However, In UC QP, a CQE with successful status of a Send Request means 
that the message was sent;
it isn't indicate that the message was received by the remote side ...
(You will get a successful CQE even if the remote side didn't receive 
this message)

>
> 2. If the status of the work completion (fetched using ibv_poll_cq())
> is IBV_WC_SUCCESS, does it mean that the operation was successful at
> the remote host (even though we used an unreliable connection)?
I answered your answer above ...

If you want some more information, you are welcome to read it in:
http://www.rdmamojo.com/2013/06/01/which-queue-pair-type-to-use/


Thanks
Dotan
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