[openib-general] uVerbs and multiple cq_event support?

[Or Gerlitz]

Arlin> If the thinking is one per CQ then is fd's the way to 
Arlin> go since we can have 1000's of CQs?

First, in the IB user space apps (eg "IB MPI" and "IB DataBase IPC") 
i am aware to there's either --one-- or --two-- CQs attached to all 
the QPs. This design simplifies the app and saves interrupts, in other 
words if you attach different CQ to each QP, your app would probably scale 
quite bad since the CPU will be busy serving interrupts per IB connection.  

Libor> The fd should become ready for read when there's a CQ event pending 
Libor> and a read of the fd will tell you which CQ it was that had the event.

Second, for an app with > 1 CQ i can think of, eg some multi-threaded IB 
server opening a thread per connection, and each thread has its own IB 
resources, one can apply the logic as Libor suggested above.

So 1 fd per process seems enough.

Or.