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Subject: Re: [OMPI devel] RFC: Linuxes shipping libibverbs
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2008-05-21 11:34:34


And there's a typo in my first paragraph. The flag currently defaults to
1 (print the warning). It should be switched to 0 to turn off the
warning. Sorry for any confusion I might have caused -- I blame the lack
of caffeine in the morning.

Brian

On Wed, 21 May 2008, Pavel Shamis (Pasha) wrote:

> I'm agree with Brian. We may add to the warning message detailed
> description how to disable it.
>
> Pasha
>
> Brian W. Barrett wrote:
>> I think having a parameter to turn off the warning is a great idea. So
>> great in fact, that it already exists in the trunk and v1.2 :)! Setting
>> the default value for the btl_base_warn_component_unused flag from 0 to 1
>> will have the desired effect.
>>
>> I'm not sure I agree with setting the default to 0, however. The warning
>> has proven extremely useful for diagnosing that IB (or less often GM or
>> MX) isn't properly configured on a compute node due to some random error.
>> It's trivially easy for any packaging group to have the line
>>
>> btl_base_warn_component_unused = 0
>>
>> added to $prefix/etc/openmpi-mca-params.conf during the install phase of
>> the package build (indeed, our simple build scripts at LANL used to do
>> this on a regular bases due to our need to tweek the OOB to keep IPoIB
>> happier at scale).
>>
>> I think keeping the Debian guys happy is a good thing. Giving them an
>> easy way to turn off silly warnings is a good thing. Removing a known
>> useful warning to help them doesn't seem like a good thing.
>>
>>
>> Brian
>>
>>
>> On Wed, 21 May 2008, Jeff Squyres wrote:
>>
>>
>>> What: Change default in openib BTL to not complain if no OpenFabrics
>>> devices are found
>>>
>>> Why: Many linuxes are shipping libibverbs these days, but most users
>>> still don't have OpenFabrics hardware
>>>
>>> Where: btl_openib_component.c
>>>
>>> When: For v1.3
>>>
>>> Timeout: Teleconf, 27 May 2008
>>>
>>> Short version
>>> =============
>>>
>>> Many major linuxes are shipping libibverbs by default these days.
>>> OMPI will therefore build the openib BTL by default, but then
>>> complains at run time when there's no OpenFabrics hardware.
>>>
>>> We should change the default in v1.3 to not complain if there is no
>>> OpenFabrics devices found (perhaps have an MCA param to enable the
>>> warning if desired).
>>>
>>> Longer version
>>> ==============
>>>
>>> I just got a request from the Debian Open MPI package maintainers to
>>> include the following in the default openmpi-mca-params.conf for the
>>> OMPI v1.2 package:
>>>
>>> # Disable the use of InfiniBand
>>> # btl = ^openib
>>>
>>> Having this in the openmpi-mca-params.conf gives Debian an easy
>>> documentation path for users to shut up these warnings when they build
>>> on machines with libibverbs present but no OpenFabrics hardware.
>>>
>>> I think that this is fine for the v1.2 series (and will file a CMR for
>>> it). But for v1.3, I think we should change the default.
>>>
>>> The vast majority of users will not have OpenFabrics devices, and we
>>> should therefore not complain if we can't find any at run-time. We
>>> can/should still complain if we find OpenFabrics devices but no active
>>> ports (i.e., don't change this behavior).
>>>
>>> But for optimizing the common case: I think we should (by default) not
>>> print a warning if no OpenFabrics devices are found. We can also
>>> [easily] have an MCA parameter that *will* display a warning if no
>>> OpenFabrics devices are found.
>>>
>>>
>>>
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>>
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