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Subject: Re: [OMPI devel] btl_openib_rnr_retry MCA param
From: Gleb Natapov (glebn_at_[hidden])
Date: 2008-02-13 00:59:48

On Tue, Feb 12, 2008 at 05:41:13PM -0500, Jeff Squyres wrote:
> I see that in the OOB CPC for the openib BTL, when setting up the send
> side of the QP, we set the rnr_retry value depending on whether the
> remote receive queue is a per-peer or SRQ:
> - SRQ: btl_openib_rnr_retry MCA param value
> - PP: 0
> The rationale given in a comment is that setting the RNR to 0 is a
> good way to find bugs in our flow control.
> Do we really want this in production builds? Or do we want 0 for
> developer builds and the same btl_openib_rnr_retry value for PP queues?
The comment is mine and IMO it should stay that way for production
builds. SW flow control either work or it doesn't and if it doesn't I
prefer to know about it immediately. Setting PP to some value greater
then 0 just delays the manifestation of the problem and in the case of
iWarp such possibility doesn't even exists.