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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.

--
			Gleb.