[openib-general] Re: [PATCH] minor fix, formatting for MAD receive handling

[Sean Hefty]

>On Wed, 2004-09-29 at 18:47, Sean Hefty wrote:
>> What I'd really like to be able to do is pull the ib_mad_private
>> receive buffer off the QP list before polling the CQ,
>> to avoid having to copy the work completion structure.
>> This would allow us to use pre-formatted
>> ib_mad_recv_wc structures as well.
>
>This requires separate CQs for send and receive so the receive
>completions are separated out. I believe that change is part of your
>still pending patch which I have not forgotten and will get to.

This is not part of the pending patch, but would be fairly easy to add to
that patch.

>You would also need to know which QPN the receive completion is for.
>I forget whether that is part of the pending patch too.

This is part of that patch.  That patch provides each QP with its own CQ, so
that the CQ context indicates the QP.

>There are also the error cases to consider.

Not all error handling is in the patch.  What isn't handled yet is reposting
or completing sends when a QP goes into the error state.

>> Along those same lines, the send path can be optimized to avoid
>> copying the work request structure for 256 byte MADs.
>
>I will look at the error cases for this too.

Avoiding the copy isn't possible in all cases, but could be in some common
ones.  A copy would need to be made to handle the case for QP overrun.  And
if we want to repost all sends after an error occurs, then we may need a
copy in all cases.  We will also need to start thinking about how RMPP will
fit into the picture as well.  A MAD that results in posting multiple work
requests makes error recovery slightly more difficult.