[openib-general] smpdump and current MAD layer
halr at voltaire.com
Thu Dec 2 12:05:39 PST 2004
On Thu, 2004-12-02 at 12:49, Sean Hefty wrote:
> Question on where to perform the snoop callback on the send side:
> should it be done in the completion handling code, immediately before
> the MAD is posted to the QP, or somewhere else?
> I'd like to place the snooping code in as few places as possible, but
> still be able to snoop locally processed MADs. Ideally a MAD should be
> snooped exactly once, which requires some extra care when handling QP
> errors. Snooping in the completion handling allows the MAD layer to
> own the thread that performs the callback. Calling clients back on the
> outbound path puts the callback in an arbitrary thread context.
While there are arguments for snooping when the MAD is posted to the QP,
I think it makes more sense to snoop it when it completes. In addition
to the thread reason you cite, one could also pass the completion status
which would give more information on what really happened (which might
be useful). I don't see a need to instrument this more than once on the
send side either.
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