Roland Dreier wrote:
> - always do peer2peer and don't let the app choose. This forces
> the overhead of p2p mode on all apps, but preserves the API.
How bad is the overhead?
- R.
The client side must send a "Ready To Receive" message. This will be
negotiated via the MPA exchange and the resulting RTR message may be a
0B read + read response, 0B write, or a 0B send. For chelsio, the 0B
write couldn't be used, and the 0B read was the least impact on the
driver code, so we used that. For nes, they currently use a 0B write.
Also, there are some "caveats" if you turn this on:
1) private data is used to negotiate the type of RTR message and if its
needed. This is more of a global module option I think, since it will
break interoperability with iwarp. Prolly will bump the MPA version
number if this option is on too.
2) if the RTR message fails, it can generate a CQE that is unexpected.
3) if using SEND, then a recv completion is always generated.
Steve.
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