On Fri, Jun 01 2018, Doug Oucharek wrote: > Would it makes sense to land LNet and LNDs on their own first? Get > the networking house in order first before layering on the file > system? I'd like to turn that question on it's head: Do we need LNet and LNDs? What value do they provide? (this is a genuine question, not being sarcastic). It is a while since I tried to understand LNet, and then it was a fairly superficial look, but I think it is an abstraction layer that provides packet-based send/receive with some numa-awareness and routing functionality. It sits over sockets (TCP) and IB and provides a uniform interface. That is almost a description of the xprt layer in sunrpc. sunrpc doesn't have routing, but it does have some numa awareness (for the server side at least) and it definitely provides packet-based send/receive over various transports - tcp, udp, local (unix domain), and IB. So: can we use sunrpc/xprt in place of LNet? How much would we need to enhance sunrpc/xprt for this to work? What hooks would be needed to implement the routing as a separate layer. If LNet is, in some way, much better than sunrpc, then can we share that superior functionality with our NFS friends by adding it to sunrpc? Maybe the answer to this is "no", but I think LNet would be hard to sell without a clear statement of why that was the answer. One reason that I would like to see lustre stay in drivers/staging (so I do not support Greg's patch) is that this sort of transition of Lustre to using an improved sunrpc/xprt would be much easier if both were in the same tree. Certainly it would be easier for a larger community to be participating in the work. Thanks, NeilBrown
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