RE: [PATCH 0/6] refactor RDMA live migration based on rsocket API

[Sean Hefty]

> > I'm sure rsocket has its place with much smaller transfer sizes, but
> > this is very different.
> 
> Is it possible to make rsocket be friendly with large buffers (>4GB) like the 
> VM
> use case?

If you can perform large VM migrations using streaming sockets, rsockets is 
likely usable, but it will involve data copies.  The problem is the socket API 
semantics.

There are rsocket API extensions (riowrite, riomap) to support RDMA write 
operations.  This avoids the data copy at the target, but not the sender.   
(riowrite follows the socket send semantics on buffer ownership.)

It may be possible to enhance rsockets with MSG_ZEROCOPY or io_uring extensions 
to enable zero-copy for large transfers, but that's not something I've looked 
at.  True zero copy may require combining MSG_ZEROCOPY with riowrite, but then 
that moves further away from using traditional socket calls.

- Sean