[openib-general] Re: [Rdma-developers] Meeting (07/22)summary:OpenRDMA community development discussion

['Christoph Hellwig']

> Can you provide more details on exactly why you think this is a horrible
> idea?  I agree it will be complex, but it _could_ be scoped such that the
> complexity is reduced.  For instance, the "offload" function could fail
> (with EBUSY or something) if there is _any_ data pending on the socket.
> Thus removing any requirement to pass down pending unacked outgoing data, or
> pending data that has been received but not yet "read" by the application.
> The idea here is that the applications at the top "know" they are going into
> RDMA mode and have effectively quiesced the connection before attempting to
> move the connection into RDMA mode.  We could, in fact, _require_ the
> connect be quiesced to keep things simpler.  I'm quickly sinking into gory
> details, but I want to know if you have other reasons (other than the
> complextity) for why this is a bad idea.

I think your writeup here is more than explanation enough.  The offload
can only work for few special cases, and even for those it's rather
complicated, especially if you take things as ipsec or complex tunneling
that get more and more common into account.  What do you archive by
implementing the offload except trying to make it look more integrated
to the user than it actually is?  Just offload rmda protocols to the
RDMA hardware and keep the IP stack out of that complexity.