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Subject: Re: [OMPI devel] [PATCH] openib: clean-up connect to allow for new cm's
From: Gleb Natapov (glebn_at_[hidden])
Date: 2007-12-12 08:28:53

On Tue, Dec 11, 2007 at 08:16:07PM -0500, Jeff Squyres wrote:
> Isn't there a better way somehow? Perhaps we should have "select"
> call *all* the functions and accept back a priority. The one with the
> highest priority then wins. This is quite similar to much of the
> other selection logic in OMPI.
> Sidenote: Keep in mind that there are some changes coming to select
> CPCs on a per-endpoint basis (I can't look up the trac ticket right
> now...). This makes things a little complicated -- do we need
> btl_openib_cpc_include and btl_openib_cpc_exclude MCA params to
> include/exclude CPCs (because you might need more than one CPC in a
> single job)? That wouldn't be hard to do.
> But then what to do about if someone sets to use some XRC QPs and
> selects to use OOB or RDMA CM? How do we catch this and print an
> error? It doesn't seem right to put the "if num_xrc_qps>0" check in
> every CPC. What happens if you try to make an XRC QP when not using
> xoob? Where is the error detected and what kind of error message do
> we print?
In my opinion "X" notation for QP specification should be removed. I
didn't want this to prevent XRC merging so I haven't raced this point.
It is enough to have two types of QPs "P" - SW credit management "S" -
HW credit management. I think connection management should work like
this: Each BTL knows what type of CPC it can use and it should share
this info during modex stage. During connection establishment modex info
is used to figure out the list of CPCs that both endpoints support and one
with highest prio is selected.