[ofa-general] IB credit-based flow control

[Sean Hefty]

>So, why is it necessary for a ULP like RDS to implement its own flow
>control? It looks like IB's flow control should result in no RNR
>retries, yet without protocol-level FC, we see RNR retries.

If you're using a shared receive queue, end to end flow control is disabled.
Also, see 9.7.7.2.5 C9-162 - an HCA is allowed to send up to one packet for a
send request even if it doesn't have any credits available.

- Sean