On Jul 16, 2008, at 7:31 PM, Underwood, Keith D wrote:
>>> [erezh] Correct; this is the scenario I was describing with the RDMA
> write.
>
> It would be interesting to see exactly what the error mode here is.
> Retransmitting corrupted data should be ok, since a correctly
> delivered
> message means that the retransmit must be dropped. I suppose that if
> the NIC speaks virtual addresses and the free actually results in a
> trap
> to the kernel that unmaps the pages, then the NIC could retransmit and
> find that there isn't a valid page table entry...
'zactly. And then the local completion entry would be a failure -- so
the sender would [erroneously] think that the message had failed to be
delivered.
> Solution #5: Change the advice to users - "...the arrival of the
> reply
> informs the sender that the send has completed and the send buffer can
> be overwritten. If the buffer will ever be freed, the application
> should call MPI_Wait or MPI_Cancel instead of MPI_Request_free."
That seems like a good compromise.
--
Jeff Squyres
Cisco Systems
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