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Subject: Re: [OMPI devel] size of shared-memory backing file + maffinity
From: Lenny Verkhovsky (lenny.verkhovsky_at_[hidden])
Date: 2009-01-13 02:55:41

Actually the size is suppose to be the same,
It just suppose to bind process to it's closer memory node, instead of
leaving it to OS.

mpool_sm_module.c:82: opal_maffinity_base_bind(&mseg, 1,

Best regards

On Mon, Jan 12, 2009 at 10:02 PM, Eugene Loh <Eugene.Loh_at_[hidden]> wrote:
> I'm trying to understand how much shared memory is allocated when maffinity
> is on.
> The sm BTL sets up a file that is mmapped into each local process's address
> space so that the processes on a node can communicate via shared memory.
> Actually, when maffinity indicates that there are multiple "memory nodes" on
> the node, then a separate file is set up and mmapped for each "memory node".
> There is an MCA parameter named "[mpool_sm_per_]peer_size", which by default
> is 32 Mbytes. The idea is that there are n processes on the node, then the
> size of the file to be mmapped in is n*32M.
> But, if there are multiple "memory nodes", will there be that much more
> shared memory? That is, is the total amount of shared memory that's mmapped
> into all the processes:
> mem_nodes * num_local_procs * peer_size
> Or, should the file for a memory node be created with size proportional to
> the number of processes that correspond to that memory node?
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