Re: [PATCH v2] RDMA/CMA: fix iWARP adapter TCP port space usage

Steve Wise
2010-07-07T16:26:14Z

Bernard Metzler wrote:
> Steve,
>
> merging the port space of different transports is very particular
> and it would be good if we could avoid it w/o losing on transport
> independence.

But the IB and IW port space is _already_ merged by the RDMA_CM. That's
my point. So a solution that breaks this impacts transport-independent
applications that use the rdma cm...

> Could we prove a strong need for that short-cut?
> If its really needed, one global RDMA_CM instance should be able
> to achive that requirement. But wouldn't that go together with a waste
> of unused transports resources (i.e., IB binds would create
> and bind also TCP sockets..?).
>

My comment has nothing to do with TCP ports but rather RDMA ports as
abstracted by the RDMA_CM. The RDMA_PS_TCP port space is shared among
all the RDMA transports. So if you rdma_bind() to port space
RDMA_PS_TCP, addr INADDR_ANY, port 9999, then it will bind the cm_id to
all IB and IW providers for that address/port (note the providers don't
really get called until rdma_listen()). Thus if you propose moving the
bind operation down into the device providers, then the IB providers
will also have to add this logic. Or some solution must be defined to
keep the IB and IW port spaces common. Otherwise the RDMA_CM cannot
support transport independent applications...

I don't think there is anything wrong with doing this, but realize this
change will impact all rdma providers as well as the core.

Steve.