It is possible that in a given poll_cq
call you end up getting on 1 completion, the other completion is
delayed due to some reason.
If a CQE is allowed to be delayed, how does polling
again guarantee that the consumer can retrieve it?
What happens if a signal occurs, there is only one CQE,
but it is delayed? ib_poll_cq would return 0 in that
case, and the consumer would never call again, thinking
the CQ is empty. There's no way the consumer can know
for sure when a CQ is drained.
If the delayed CQE happens only when there is more
than one CQE, how can polling multiple WCs ever work
reliably?
Maybe I don't understand what is meant by delayed.
If I'm not mistaken, Devesh meant that if between ib_poll_cq (where you
polled the last 2 wcs) until the while statement another CQE was
generated then you lost a bit of efficiency. Correct?
Would it be better to poll for 1 in every
poll call Or
otherwise have this
while ( rc <= ARRAY_SIZE(wcs) && rc);
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