[ofa-general] Re: Re: [PATCH RFC] sharing userspace IB objects

[Hal Rosenstock]

On Sun, 2007-07-01 at 15:05, Gleb Natapov wrote:
> On Sun, Jul 01, 2007 at 07:27:24PM +0300, Dror Goldenberg wrote:
> > > SSQ is needed for scalability, no need to explain this (by 
> > > the way RD is needed for the same reason too. What's Mellanox 
> > > plan to support it?
> > 
> > RD is not supported in hardware today. Implementing RD is extremely 
> > complicated. To solve the scalability issues on MPI like applications
> > we believe that SRC and SSQ are the right solutions. It is much simpler
> > for implementation by both software and hardware. By MPI-like I refer
> > to applications that have some level of trust between two processes of
> > the
> > same application. RD also has some performance issues as it only 
> > supports one message in the air. Those performance issues are solved
> > by design in SRC/SSQ.
> > 
> Didn't know about RD limitation. Is this shortcomings of IB spec or
> general limitation of reliable datagram? RD looks much nice to me then SRC/SSQ.

I think Dror is referring to number of messages in flight per EEC and
number of messages in flight per QP being limited to 1 per IBA spec.
Number of messages enqueued per EEC/QP is implementation dependent.

-- Hal

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