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Subject: Re: [OMPI devel] RFC: Linuxes shipping libibverbs
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-05-21 22:46:19


Brian and I chatted a bit about this off-list, and I think we're in
agreement now:

- do not change the default value or meaning of
btl_base_want_component_unsed.

- major point of confusion: the openib BTL is actually fairly unique
in that it can (and does) tell the difference between "there are no
devices present" and "there are devices, but something went wrong".
Other BTL's have network interfaces that can't tell the difference and
can *only* call the no_nics function, regardless of whether there are
no relevant network interfaces or some error occurred during
initialization.

- so a reasonable solution would be an openib-BTL-specific mechanism
that doesn't call the no_nics function (to display that
btl_base_want_component_unused) if there are no verbs-capable devices
found because of the fact that mainline Linuxes are starting to ship
libibverbs. Specific mechanism TBD; likely to be an openib MCA param.

On May 21, 2008, at 9:56 PM, Jeff Squyres wrote:

> On May 21, 2008, at 5:02 PM, Brian W. Barrett wrote:
>
>> If this is true (for some reason I thought it wasn't), then I think
>> we'd
>> actually be ok with your proposal, but you're right, you'd need
>> something
>> new in the IB btl. I'm not concerned about the dual rail issue -- if
>> you're smart enough to configure dual rail IB, you're smart enough to
>> figure out OMPI mca params. I'm not sure the same is true for a
>> simple
>> delivered from the white box vendor IB setup that barely works on a
>> good
>> day (and unfortunately, there seems to be evidence that these exist).
>
>
> I'm not sure I understand what you're saying -- you agree, but what
> "new" do you think we need in the openib BTL? The MCA params saying
> which ports you expect to be ACTIVE?
>
> --
> Jeff Squyres
> Cisco Systems
>
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-- 
Jeff Squyres
Cisco Systems