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Hmm, I do amortize the cost of ibv_ack_cq_event() over multiple
ibv_get_cq_event()
calls; however when the shutdown is in progress I don't have the last
event that was "gotten" so I have to call ibv_get_cq_event()
one last time to get an event to acknowledge against. I suppose it's
probably better to keep the last event processed if it hasn't been
acknowledged and use it to issue the final acknowledge when shutting
down. Then I wouldn't have to make that ibv_get_cq_event()
call.<br>
<br>
One last question, when I create the completing event queue I set it to
non-blocking but I find that during shutdown I have to do that again
before making the final call to ibv_get_cq_event() otherwise it blocks.
Which I suppose is why it returns EAGAIN when there are no pending
events, but I don't understand why I have to set it to non-blocking
again.<br>
<br>
Anyway, much thanks for all your help.<br>
<br>
Nitin<br>
<br>
Sean Hefty wrote:
<blockquote
cite="mid:9A7396C9CD4746EA9474428B1BB6F0EA@amr.corp.intel.com"
type="cite">
<blockquote type="cite">
<pre wrap="">I guess my question is, what's the best way to destroy IB resources? (Perhaps
even, what's the best way to init them in the first place).
</pre>
</blockquote>
<pre wrap=""><!---->
If you're destroying the CQ, there's no need to call ibv_get_cq_event() or
ibv_poll_cq(), unless you need completion information (for example, from flushed
receives).
However, every successful call to ibv_get_cq_event() needs a corresponding call
to ibv_ack_cq_event(). You can call ack(1) for each cq event, or count the
number of times that get returns success and call ack(get_cnt) once before
calling destroy. Note that the count refers to the number of cq events, and not
the number of completions returned through ibv_poll_cq.
For your drain_cq() function, you should be safe doing something like this:
while (ibv_poll_cq(...) > 0)
/* optional processing of any left over completions */;
ibv_ack_cq_event(...this_cqs_total_event_cnt); /* or ack after get */
ibv_destroy_cq(...);
</pre>
<blockquote type="cite">
<pre wrap="">ibv_dealloc_pd(), ibv_destroy_cq() and ibv_destroy_comp_channel() all return
error EBUSY
</pre>
</blockquote>
<pre wrap=""><!---->
This sounds like a QP isn't being destroyed. I'm not sure that anything else
fails CQ destruction with EBUSY.
Btw, if you're using the rdma_cm interface, then it's simpler to use the
rdma_create_qp/rdma_destroy_qp calls, which allows the rdma_cm to perform the QP
state transitions for you.
- Sean
</pre>
<pre wrap="">
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</pre>
</blockquote>
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