[PATCH RFC] nvme-rdma: support devices with queue size < 32

[Sagi Grimberg]

>> For each I/O we post up to 2 work requests, 1 for memory registration
>> and 1 for sending an I/O request (and 1 for local invalidation if the
>> target doesn't do it for us, but that is not the case here). So if our
>> queue depth is X, we size our completion queue to be X*3, and we need
>> to make sure we signal every (X*3)/2.
>
> ??? If your SQ is X and your CQ is X*3 you need to signal at X/2.

Sorry, I confused SQ with CQ (which made it even more confusing..)

Our application queue-depth is X, we size our SQ to be X*3
(send+reg+inv), we size our RQ to be X (resp) and our CQ to be
X*4 (SQ+RQ).

So we should signal every (X*3)/2