I expect that yes, it would be useful to use RIO with Node.
What I'm hoping to find, once I've got RIO integrated into my IOCP framework, is that 'faster path' from user mode send/recv calls to/from the network stack will result in performance improvements for IOCP based servers that switch to using RIO. It likely wont be as much as if you used RIO in a tight loop polled situation, but you should still get some benefits from the pre-locked buffers and the reduced amount of work needed during send and recv calls. Going via the IOCP for completion notification will result in some kernel mode transitions but it's necessary to allow you to scale RIO to many thousands of connections.
I'll post some comparative perf tests once I've got a bit further.
What I'm hoping to find, once I've got RIO integrated into my IOCP framework, is that 'faster path' from user mode send/recv calls to/from the network stack will result in performance improvements for IOCP based servers that switch to using RIO. It likely wont be as much as if you used RIO in a tight loop polled situation, but you should still get some benefits from the pre-locked buffers and the reduced amount of work needed during send and recv calls. Going via the IOCP for completion notification will result in some kernel mode transitions but it's necessary to allow you to scale RIO to many thousands of connections.
I'll post some comparative perf tests once I've got a bit further.