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Subject: Re: [OMPI users] Myrinet optimization with OMP1.3 and macosX
From: Ricardo Fernández-Perea (rfernandezperea_at_[hidden])
Date: 2009-05-07 05:09:04

I just did, at least the ping pong, the results are slightly worst and
 presents the same drop at 64KSee attachment.

a comment: to run with the btl mx i need to use --mca btl mx,sm,self -mca
mtl ^mx or i get a mx_open_endpoint failure due to myrinet busy (I have
already increase the number of endpoints to 16 )

On Wed, May 6, 2009 at 7:31 PM, Scott Atchley <atchley_at_[hidden]> wrote:

> On May 4, 2009, at 10:54 AM, Ricardo Fernández-Perea wrote:
> I finally have opportunity to run the imb-3.2 benchmark over myrinet I am
>> running in a cluster of 16 node Xservers connected with myrinet 15 of them
>> are 8core ones and the last one is a 4 cores one. Having a limit of 124
>> process
>> I have run the test with the bynode option so from the 2 to the 16 process
>> test is always running 1 process by node.
>> the following test pingpong, pingping, sendrecv, exchange presents a
>> strong drop in performance with the 64k packet size.
>> any idea where I should look for the cause.
>> Ricardo
> Hi Ricardo,
> I believe that the pingpong results show the drop that you are
> experiencing. There is a drop at 64 KB and 128 KB and it returns to the same
> level at 128 KB.
> What you are seeing in the pingpong results is the change over from eager
> to rendezvous within MX. Up to 32 KB, we use an eager protocol (send the
> data even if there is not a posted receive). After 32 KB, we switch to a
> rendezvous protocol.
> I do not believe that this limit can be changed. Have you tried the same
> application when using the MX BTL?
> Scott
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