Roland Dreier wrote:
Michael> So, here we have a long discussion on attempting to
Michael> perpetuate a concept that is not universal across
Michael> transports and was deemed to have minimal value that most
Michael> wanted to see removed from the architecture.
But this discussion is being driven by an application developer who
does see value in immediate data.
Arlin, can you quantify the benefit you see from RDMA write with
immediate vs. RDMA write followed by a send?
We need speed and simplicity.
A very latency sensitive application that requires immediate
notification of RDMA write completion on the remote node without ANY
latency penalties associated with combining operations, HCA priority
rules across QPs, wire congestion, etc. An application that has no
requirement for messaging outside of remote rdma write completion
notifications. The application would not have to register and manage
additional message buffers on either side, we can just size the queues
accordingly and post zero byte messages. We need something that would be
equivelent to setting there polling on the last byte of inbound data.
But, since data ordering within an operation is not guaranteed that is
not an option. So, rdma with immediate data is the most optimal and
simplistic method for indication of RDMA-write completion that we have
available today. In fact, I would like to see it increased in size to
make it even more useful.
-arlin
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