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Subject: Re: [OMPI users] Gigabit ethernet (PCI Express) and openmpi v1.2.4
From: Allan Menezes (amenezes007_at_[hidden])
Date: 2007-12-18 00:44:54


Hi,
  I found the problem. It's a bug with openmpi v 1.2.4 i think. As below
tests confirm(AND an big THANKS to George!) I compiled openmpi v
1.3a1r16973 and tried the same tests with the same mca-params.conf file
and got for three pci express gigabit ethernet cards a total bandwidth
of 2583Mbps which is close to 892+892+888=2672Mbps for a linear
increase in b/w everything else the same except for a recompilation of
NPmpi and Nptcp of netpipe. NPmpi uses mpicc to compile NPmpi whereas
NPtcp is compiled with gcc!
I am now going to do some benchmarking with hpl of my basement cluster
with openmpi v 1.3a1r16973 for increase in performnce and stability. V
1.2.4 is stable and completes all 18 hpl tests without errors!
With openmpi v1.24 and NPmpi compiled wit's mpicc and using the shared
memory commands below in --(a) I get for ./NPmpi -u 100000000 negative
numbers for performance above approx 200Mbytes.
Some sort of overflow in v1.2.4.
Thank you,
Regards,
Allan Menezes

Hi George, The following test peaks at 8392Mpbs: mpirun --prefix
/opt/opnmpi124b --host a1,a1 -mca btl tcp,sm,self -np 2 ./NPmpi on a1
and on a2

mpirun --prefix /opt/opnmpi124b --host a2,a2 -mca btl tcp,sm,self -np 2 ./NPmpi
gives 8565Mbps
--(a)
on a1:
mpirun --prefix /opt/opnmpi124b --host a1,a1 -np 2 ./NPmpi

gives 8424Mbps on a2:

mpirun --prefix /opt/opnmpi124b --host a2,a2 -np 2 ./NPmpi

gives 8372Mbps So theres enough memory and processor b/w to give 2.7Gbps
for 3 pci express eth cards especially from --(a) between a1 and a2?
Thank you for your help. Any assistance would be greatly apprectiated!
Regards, Allan Menezes You should run a shared memory test, to see
what's the max memory bandwidth you can get. Thanks, george. On Dec 17,
2007, at 7:14 AM, Gleb Natapov wrote:

>> On Sun, Dec 16, 2007 at 06:49:30PM -0500, Allan Menezes wrote:
>
>
>>>> Hi,
>>>> How many PCI-Express Gigabit ethernet cards does OpenMPI version
>>>> 1.2.4
>>>> support with a corresponding linear increase in bandwith measured
>>>> with
>>>> netpipe NPmpi and openmpi mpirun?
>>>> With two PCI express cards I get a B/W of 1.75Gbps for 892Mbps each
>>>> ans
>>>> for three pci express cards ( one built into the motherboard) i get
>>>> 1.95Gbps. They all are around 890Mbs indiviually measured with
>>>> netpipe
>>>> and NPtcp and NPmpi and openmpi. For two it seems there is a linear
>>>> increase in b/w but not for three pci express gigabit eth cards.
>>>> I have tune the cards using netpipe and $HOME/.openmpi/mca-
>>>> params.conf
>>>> file for latency and percentage b/w .
>>>> Please advise.
>>
>>
>> What is in your $HOME/.openmpi/mca-params.conf? May be are hitting
>> your
>> chipset limit here. What is your HW configuration? Can you try to run
>> NPtcp on each interface simultaneously and see what BW do you get.
>>
>> --
>> Gleb.
>