[rds-devel] [ofa-general] [RFC] dropping RDS over TCP support

[Richard Frank]

Or Gerlitz wrote:
> On Tue, Sep 2, 2008 at 11:04 PM, Andy Grover <andy.grover at oracle.com 
> <mailto:andy.grover at oracle.com>> wrote:
>
>     We've been discussing dropping RDS's support for using TCP as a
>     transport, and just focusing on RDS as a IB and iWARP-focused
>     protocol.
>
>
> do we have any results that compare Oracle IPC using rds/bcopy/tcp vs udp?
>
Nothing current - would be great to see rds-stress data for RDS/TCP over 
10GE compared to RDS/IB over 10GIB and RDS/IWARP over 10G.

The purpose of the TCP transport was to support simple ethernet NICs 
with bcopy.
Our thinking at the time was that TCP (even if the path lengths are 
longer than UDP) would
be more efficient under heavy load - than running UDP from user mode.

>     This would simplify the RDS codebase, allow easier inclusion of
>     more IB-centric features, and also give RDS an easier path towards
>     mainline Linux kernel inclusion. Also, the imminent RDS iWARP
>     support will address non-IB use cases.
>
>
> So just to make sure, do IB and iWARP  share the same transport code 
> today? if yes, does removing TCP means the transport abstraction would 
> not be needed any more, or you still want to maintain it for the 
> loopback case? Generally speaking, the loopback transport also uses 
> IB, correct? and if it doesn't I am quite sure it can.
>
> I tend to agree with Jon that removing TCP might help with mainline 
> inclusion or might create damage...
>
Why does having the TCP module affect the issue of main line inclusion - 
what is / are the issues ?

> Roland, maybe you have more definitive intuitions re the netdev people 
> potential feedback on rds as a new socket type applicable to RDMA 
> cards such as IB and iWARP using a verbs/rdmacm native transport AND 
> to non RDMA cards with TCP transport, vs the case of RDS being "just" 
> a ULP under drivers/infiniband/ulps that defines a new socket type, etc.
>
>
> Or
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