[ofa-general] missed cq event

[Steve Wise]

Philip Frey1 wrote:
>
> > > what is the correct way to get completions from the CQ without 
> missing
> > > any?
> > > I am currently using two separate CQs for the SQ and for the RQ.
> > > In pseudocode I do about the following to wait for a completion:
> > >
> > > ibv_get_cq_event(channel, &dst_cq, &ctx);        //blocking wait for
> > > CQ event
> > > <-- EVENT -->
> > > ibv_req_notify_cq(dst_cq, 0);                        // request event
> > > for next completion
> > > ibv_poll_cq(dest_cq, 1, wc);                        // get the WC 
> from
> > > the CQ
> > > ibv_ack_cq_events(dst_cq, 1);                        // ack the event
> > >
>
> < snip >
>
> >
> > you need to poll the cq until it is empty instead of just polling once.
> >
> >
> > get_cq_event()
> > req_notify_cq()
> > do {
> >     ne = poll_cq();
> > } while (ne != 0);
> > ack_cq_event()
>
> But what if I am just interested in the next work completion? Wouldn't 
> this mean
> that I have to build a queue in my application, that can hold 
> completions in which
> I am not yet interested? It sounds like a replication of the 
> completion queue to me.
> I was more looking for a way to do the 'single poll' on the completion 
> without copying
> anything into another queue.

You can process each polled CQE individually inside the loop, yes?  How 
is that different from getting notified of each CQE insertion and 
processing it then?