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Subject: Re: [OMPI devel] trac #2034 : single rail openib btl shows better bandwidth than dual rail (12k< x < 128k)
From: Don Kerr (Don.Kerr_at_[hidden])
Date: 2009-10-06 11:14:07


I agree there is probably a larger issue here and yes this is somewhat
specific but where as OB1 appears to have multiple protocols depending
on the capabilities of the BTLs I would not characterize as an IB
centric problem. Maybe OB1 RDMA problem. There is a clear benefit from
modifying this specific case. Do you think its not worth making
incremental improvements while also attacking a potential bigger issue?

-DON

On 10/06/09 10:52, George Bosilca wrote:
> Don,
>
> This seems a very IB centric problem (and solution) going up in the
> PML. Moreover, I noticed that independent on the BTL we have some
> problems with the multi-rail performance. As an example on a cluster
> with 3 GB cards we get the same performance is I enable 2 or 3. Didn't
> had time to look into the details, but this might be a more general
> problem.
>
> george.
>
> On Oct 6, 2009, at 09:51 , Don Kerr wrote:
>
>>
>> I intend to make the change suggested in this ticket to the trunk.
>> The change does not impact single rail, tested with openib btl, case
>> and does improve dual rail case. Since it does involve performance
>> and I am adding a OB1 mca parameter just wanted to check if anyone
>> was interested or had an issue with it before I committed the change.
>>
>> -DON
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