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Subject: [OMPI devel] sendrecv_replace: long time to allocate/free memory
From: Pascal Deveze (Pascal.Deveze_at_[hidden])
Date: 2010-04-22 08:50:24


Hi all,

The sendrecv_replace in Open MPI seems to allocate/free memory with
MPI_Alloc_mem()/MPI_Free_mem()

I measured the time to allocate/free a buffer of 1MB.
MPI_Alloc_mem/MPI_Free_mem take 350us while malloc/free only take 8us.

malloc/free in ompi/mpi/c/sendrecv_replace.c was replaced by
MPI_Alloc_mem/MPI_Free_mem with this commit :

user: twoodall
date: Thu Sep 22 16:43:17 2005 +0000
summary: use MPI_Alloc_mem/MPI_Free_mem for internally allocated
buffers

Is there a real reason to use these functions or can we move back to
malloc/free ?
Is there a problem on my configuration explaining such slow performance
with MPI_Alloc_mem ?

Pascal