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Subject: Re: [OMPI users] OpenIB problems
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2007-11-28 11:28:10


Roland thought that the default value of 10 might be a bit too low and
that tuning it to be higher, particularly in apps that pound on a
single port, would probably be acceptable.

Tuning up to 20 is probably a bit overkill.

On Nov 27, 2007, at 3:54 PM, Jeff Squyres wrote:

> 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
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> --
> Jeff Squyres
> Cisco Systems
>
>

-- 
Jeff Squyres
Cisco Systems