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

Steve Wise
2010-06-12T02:10:17Z

Jason Gunthorpe wrote:
> On Fri, Jun 11, 2010 at 08:18:43PM -0500, Steve Wise wrote:
>
>
>> Further, its not even needed for IB, just iWARP. That's an unnecessary
>> admin pain IMO.
>>
>
> IB already completely seperates from the host stack, that is why it
> isn't effected by this problem. It has both a seperate port numbering
> space (in rdma cm) and a separate addressing space (GID).
>
>

By virtue of being a different L4 transport. iWARP uses TCP as the L4
and thus has these issues.

Also, from an application perspective, IB has IP addresses that are
shared with the TCP stack and the RDMA stack. So it still appears as
integrated. At least with librdmacm applications...

> The entire problem with iWARP is that it is trying to not be
> seperate, unlike IB. So.. simple answer: use a seperate IP, or use a
> seperate port space (ie don't use the TCP protocol number).
>

Change the iWARP specification? I don't think that's a simple answer. :)

> ROCEE won't have this problem either..
>
>
>> iWARP should and can easily co-exist with the host TCP by sharing
>> the port space. But, as Roland stated already, maybe the only way
>> forward it to get end-user pressure applied at the appropriate
>> places! :)
>>
>
> *shrug* This isn't going to happen until netdev decides to design-in
> statefull offload. I doubt that is going to happen any time
> soon. I've already seen Linux max out 40GE on benchmarks, so it is
> hard to see what the driver would be.
>
> Jason
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