[ofa-general] Managing work completions (libibverbs)

[Kelly Burkhart]

> -----Original Message-----
> From: Roland Dreier [mailto:rdreier at cisco.com] 
> 
> You can use epoll to get comp channel events, but you'll need 
> to collect
> the event with ibv_get_cq_event() to rearm things.  epoll 
> tells you when
> the fd becomes readable, but you'll need to actually read all the
> events queued on the fd before waiting again.  The overhead of
> ibv_get_cq_event() should not be too high compared to the overhead of
> sleeping and getting woken up again by an interrupt, and you 
> can always
> amortize ibv_ack_cq_events() by just keeping a counter of the 
> number of
> events you read and only calling ibv_ack_cq_events() occasionally.


Digging through the code to see what resource I hog if I don't ack
frequently enough:  It appears that ibv_ack_cq_events only increments
an integer in the CQ (and doesn't free or return some resource).  So I
could just count gets and ack them all immediately prior to
destructing the CQ.

Why be so picky about matching acks with gets?

-K