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Subject: Re: [OMPI users] Buffer size limit and memory consumption problem on heterogeneous (32 bit / 64 bit) machines
From: Nysal Jan (jnysal_at_[hidden])
Date: 2010-05-20 06:44:53


This probably got fixed in https://svn.open-mpi.org/trac/ompi/ticket/2386
Can you try 1.4.2, the fix should be in there.

Regards
--Nysal

On Thu, May 20, 2010 at 2:02 PM, Olivier Riff <oliriff_at_[hidden]>wrote:

> Hello,
>
> I assume this question has been already discussed many times, but I can not
> find on Internet a solution to my problem.
> It is about buffer size limit of MPI_Send and MPI_Recv with heterogeneous
> system (32 bit laptop / 64 bit cluster).
> My configuration is :
> open mpi 1.4, configured with: --without-openib --enable-heterogeneous
> --enable-mpi-threads
> Program is launched a laptop (32 bit Mandriva 2008) which distributes tasks
> to do to a cluster of 70 processors (64 bit RedHat Entreprise
> distribution):
> I have to send various buffer size from few bytes till 30Mo.
>
> I tested following commands:
> 1) mpirun -v -machinefile machinefile.txt MyMPIProgram
> -> crash on client side ( 64 bit RedHat Entreprise ) when sent buffer size
> > 65536.
> 2) mpirun --mca btl_tcp_eager_limit 30000000 -v -machinefile
> machinefile.txt MyMPIProgram
> -> works but has the effect of generating gigantic memory consumption on 32
> bit machine side after MPI_Recv. Memory consumption goes from 800Mo to 2,1Go
> after receiving about 20ko from each 70 clients ( a total of about 1.4 Mo
> ). This makes my program crash later because I have no more memory to
> allocate new structures. I read in a openmpi forum thread that setting
> btl_tcp_eager_limit to a huge value explains this huge memory consumption
> when a message sent does not have a preposted ready recv. Also after all
> messages have been received and there is no more traffic activity : the
> memory consumed remains at 2.1go... and I do not understand why.
>
> What is the best way to do in order to have a working program which also
> has a small memory consumption (the speed performance can be lower) ?
> I tried to play with mca paramters btl_tcp_sndbuf and mca btl_tcp_rcvbuf,
> but without success.
>
> Thanks in advance for you help.
>
> Best regards,
>
> Olivier
>
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