If I call MPI_Win_allocate for e.g. 8 bytes, does it allocate shared memory every time, and thus potentially allocate with page alignment, which could cause a lot of empty VM space? Perhaps I do not understand POSIX shared memory well enough, but it strikes me that it might be a worthwhile optimization to have a memory pool for small-size MPI_Win_allocate(_shared) calls. Thanks, Jeff -- Jeff Hammond [email protected] http://jeffhammond.github.io/