I suspect this is the shared memory used to communicate between processes.
Please run your application adding the flag "--mca btl tcp,self" to the
mpirun command line (*before the application name). If the virtual memory
usage goes down then the 400MB are definitively comming from the shared
memory and there are ways to limit this amount
(http://www.open-mpi.org/faq/?category=tuning provide a full range of
options).
Otherwise ... we will have to find out where they come from differently.
Thanks,
george.
On Fri, 25 Aug 2006, Miguel Figueiredo Mascarenhas Sousa Filipe wrote:
Hi there,
I'm using openmpi-1.1 on a linux-amd64 machine and also a linux-32bit x86
chroot environment on that same machine.
(distro is gentoo, compilers: gcc-4.1.1 and gcc-3.4.6)
In both cases openmpi-1.1 shows a +/-400MB overhead in virtual memory usage
(virtual address space usage) for each MPI process.
In my case this is quite troublesome because my application in 32bit mode is
counting on using the whole 4GB address space for the problem set size and
associated data.
This means that I have a reduction in the size of the problems which it can
solve.
(my aplication isn't 64bit safe yet, so I need to run in 32bit mode, and use
effectively the 4GB address space)
Is there a way to tweak this overhead, by configuring openmpi to use smaller
buffers, or anything else ?
I do not see this with mpich2.
Best regards,
"We must accept finite disappointment, but we must never lose infinite
hope."
Martin Luther King
