[ofa-general] [PATCH] ib_send_bw -b can hang due to too few CQ entries

[Sean Hefty]

>Remember that this fix only affects the bi-directional test.
>Both client and sever are going to post ctx->rx_depth receives
>and ctx->tx_depth sends and then check for completions.
>It won't post more sends or receives until the completions are
>seen.

Okay - I think I understand what's happening.

The maximum number of outstanding sends is limited to tx_depth / 2.  After
posting that many sends, the code waits for completions.  Once some sends
complete, additional sends may be posted, up to the iteration count.  There's
nothing that coordinates posting the sends with completing receives on the
remote side.  (This is what I was missing.)  Eventually, all posted receives
could be complete and generate CQ entries.  The send side is basically throttled
by RNR NACKs.

Now I don't understand the purpose behind doubling the rx_depth...

- Sean