[openib-general] Verbs QP create with RQ=0?

[Roland Dreier]

 > We have an application that doesn't require a receive CQ or QP resources
 > since it will never post receive messages. We are attempting to limit
 > our resources and reduce our receive resources to zero but it appears
 > that the create qp assumes a receive CQ is always provided. According to
 > the specification this appears to be correct, but it is not clear what
 > the minimum requirements are for the receive CQ and QP resources. What
 > are your recommendations for creating a QP with no recv QP/CQ resources?
 > Is it possible to create receive queue of 0?

As was already suggested, you should be able to use the same CQ for
receives and for sends.  If you never post any receives on the QP, you
don't have to allocate any extra space on your send CQ.  And it should
work to have 0 receive work queue entries.  Have you tried it?

I think there actually is a bug in mthca that prevents creating a QP
with both the send queue and receive queue of size 0 (which would be
useful as an RDMA target), but I don't think that's what you're
running into.  That's on my list of things to chase down, but it
hasn't been a real issue for anyone (as far as I know) so the priority
is not high for me.

 - R.