[ofa-general] Re: [PATCH RFC] RDMA/CMA: Allocate PS_TCP ports from the host TCP port space.

[Steve Wise]

Sean Hefty wrote:
>> If we get rid of the rdma_cm specific port spaces, do we then reduce 
>> the  valid possible spaces to just TCP and UDP?  Or what?  In the 
>> sockets paradigm, the socket is explicitly bound to a protocol space 
>> when its created (based on the protocol id).  Do you think we need to 
>> change the rdma_cm_id to have such a concept?  IE when you create the 
>> cm_id, you say your intended QP type or port space?  The current API 
>> lends itself to somone incorrectly choosing a port space, by the way.
> 
> Currently, the RDMA port space implies the QP type (RC or UD).  We're 
> not tied to any specific protocol when we create the rdma_cm_id, since 
> we don't know what type of RDMA device we'll end up using.  So, I don't 
> think we want users to specify a protocol.
> 
>> But should we really change the API that drastically?  Or just keep 
>> the port spaces and make PS_TCP share the host's port space.
> 
> I don't want to break the user space API, if it can be helped.  SDP is 
> kind of a problem, in that the rdma_cm needs to distinguish between SDP 
> as a user, versus someone using RDMA_PS_TCP.  SDP maps between the RDMA 
> port space and real TCP port space.  I need to get some details on how 
> SDP uses the rdma_cm, like whether it uses wild card port numbers.
> 
>> Maybe the rdma-cm port spaces should really be IB, IWARP, or BOTH.  IB 
>> has its own port space, and IWARP or BOTH gets the TCP port space.
> 
> I thought about doing something like this, but I'm not sure there would 
> be much use of just IB or just iWarp, when the user can specify both.  I 
> even considered pushing the problem into the iWarp CM, but that seems 
> like a more complex implementation with no benefit unless there are 
> users of just an IB port space.
> 
> At this point, my thoughts are to take your original patch, remove the 
> rdma_cm port space structures and functions, and figure out how to 
> handle SDP.
> 

Lemme know how I can help.  I certainly can test any patches on my 8 
node iwarp cluster.


Steve.