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Subject: Re: [OMPI users] OpenIB problems
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2007-11-27 16:54:01


BTW, Andrew is correct about the unit for btl_openib_ib_timeout and
that the value is simply passed down to the verbs library when making
an IB connection. Open MPI does nothing else with that value; it's an
IBTA-defined value.

The help message was wrong on the 1.2 branch for a while; I think it's
been corrected in more recent versions of OMPI (i.e., >1.2 -- I don't
recall which version specifically).

On Nov 27, 2007, at 3:19 PM, Andrew Friedley wrote:

>
>
> Brock Palen wrote:
>>>> What would be a place to look? Should this just be default then
>>>> for
>>>> OMPI? ompi_info shows the default as 10 seconds? Is that right
>>>> 'seconds' ?
>>> The other IB guys can probably answer better than I can -- I'm not
>>> an
>>> expert in this part of IB (or really any part I guess :). Not sure
>>> why
>>> a larger value isn't the default. No, its not seconds -- check the
>>> description of the MCA parameter:
>>>
>>> 4.096 microseconds * (2^btl_openib_ib_timeout)
>>
>> You sure?
>> ompi_info --param btl openib
>>
>> MCA btl: parameter "btl_openib_ib_timeout" (current value: "10")
>> InfiniBand transmit timeout, in seconds
>> (must be >= 1)
>
> Yeah:
>
> MCA btl: parameter "btl_openib_ib_timeout" (current value: "10")
> InfiniBand transmit timeout, plugged into formula:
> 4.096 microseconds * (2^btl_openib_ib_timeout)(must be
>> = 0 and <= 31)
>
> Reading earlier in the thread you said OMPI v1.2.0, I got this from a
> trunk checkout thats around 3 weeks old. A quick check shows this
> description was changed between 1.2.0 and 1.2.1. However the use of
> this parameter hasn't changed -- it's simply passed along to IB verbs
> when creating a queue pair (aka a connection).
>
> Andrew
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-- 
Jeff Squyres
Cisco Systems