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Subject: Re: [OMPI devel] OMPI OpenIB Credit Schema breaks Chelsio HW
From: Gleb Natapov (glebn_at_[hidden])
Date: 2008-03-10 12:48:59


On Mon, Mar 10, 2008 at 09:50:13AM -0500, Steve Wise wrote:
> > I personally don't like the idea to add another layer of complexity to openib
> > BTL code just to work around HW that doesn't follow spec. If work around
> > is simple that is OK, but in this case it is not so simple and will add
> > code path that is rarely tested. A simple workaround for the problem may
> > be to not configure multiple QPs if HW has a bug (and we can extend ini
> > file to contain this info).
> >
> >
>
> It doesn't sound too complex to implement the above design. In fact,
> that's the way this btl used to work, no? There are large customers
> requesting OMPI over cxgb3 and we're ready to provide the effort to get
> this done. So I request we come to an agreement on how to support this
> device efficiently (and for ompi-1.3).
Yes. The btl used to work like that before. But the current way of doing
credit management requires much less memory, so I don't think reverting
to the old way is a right thing. And having two different ways of
sending credit updates seems like additional complexity. The problem is
not just with writing code, but this code will have to be maintained for
unknown period of time (will this problem be solved in your next gen HW?).
I am OK with adding old fc in addition to current fc if the code is trivial
and easy to maintain. Do you think it is possible to add what you want
and meet these requirements?

--
			Gleb.