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Subject: Re: [OMPI devel] RFC: Linuxes shipping libibverbs
From: Pavel Shamis (Pasha) (pasha_at_[hidden])
Date: 2008-05-22 05:26:42


> 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.
>
Ok, we will have own warning mechanism. But we still open question, Will
we show (by default) error message in case
when libibverbs exists but it is no hca in the hca_list ?
I think we should show the error. The problem of libibverbs default
install is relevant only for
binary distribution, that install all ompi dependences with ompi
package. In this case
distribution will have openib mca parameter that will allow to disable
by default the warning message
during ompi package install (or build).
I guess that most people still install ompi from sources. And in this
case it sound reasonable for me
to print this "no hca" warning it openib btl was build.

Pasha

>
> 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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>
>
>