[openib-general] Re: CMA stuff

[Sean Hefty]

Michael S. Tsirkin wrote:
>>The QP is in the INIT state after rdma_create_qp() is called.  Receives may 
>>be posted at that time.
> 
> I'm talking about the passive side.

Active or passive side doesn't matter.  rdma_create_qp() returns the QP in the 
INIT state.  On the passive side, this would be called only after an 
RDMA_CM_EVENT_CONNECT_REQUEST had been received.

>>What are you wanting it to do with it?  It's possible that what you're 
>>looking for is done by the IB CM.
> 
> Pass it to QP in an ah?

The IB CM initializes QP attributes based on values in the CM exchange messages. 
  The CMA invokes the IB CM calls to initialize QP attributes rather than 
setting them itself.

> My idea was to have 2 counters: one counting connections
> that are being established, gong up to tcp_max_syn_backlog,
> and another one after the connection is established, up to local
> socket backlog.

My understanding is that with sockets, backlog is the number of queued 
connections not yet accepted by the user.  With the CMA, connection requests are 
explicitly accepted by the user before the connection is established. 
Connection requests are reported to the user directly through a callback, rather 
than being queued until the user comes to claim them.

- Sean