[PATCH v3 0/9] Introduce per-device completion queue pools

[Bart Van Assche]

On Thu, 2017-11-09 at 19:22 +0200, Sagi Grimberg wrote:
> But I'm afraid don't understand how the fact that ULPs will run on
> different ports matter? how would the fact that we had two different
> pools on different ports make a difference?

If each RDMA port is only used by a single ULP then the ULP driver can provide
a better value for the CQ size than IB_CQE_BATCH. If CQ pools would be created
by ULPs then it would be easy for ULPs to pass their choice of CQ size to the
RDMA core.

In case multiple ULPs share an RDMA port then which CQ is chosen for the ULP
will depend on the order in which the ULP drivers are loaded. This may lead to
hard to debug performance issues, e.g. due to different lock contention
behavior. That's another reason why per-ULP CQ pools look more interesting to
me than one CQ pool per HCA.

Bart.