On Wed, Aug 08, 2007 at 06:47:41PM -0500, Sam Lang wrote: > Also, should we increase the limit of request segments allowed? It > might be inefficient for a user to create an MPI indexed dataype with > that many elements, but there are users that will probably do it > anyway. Alternatively, we could consider more efficiently encoding > each request segment in PVFS.
Bear in mind that Joe User is probably going to create these PVFS types through ROMIO. Since we take a list-io approach and turn all types into offset-length pairs (the indexed type), what could be a very compact MPI type might become a quite long PVFS type (for example, some of the types created by the HDF5 test programs contain 512 offset-length pairs once they make their way down to ADIOI_PVFS2_WriteStrided) I'd like to see a few things: - a way to ask PVFS how many segments romio can produce. that's hard-coded to 64 now, but clearly should have been less in this case and more for TCP. - a way to announce to PVFS "hey, i'm about to send you a giant request". I'm 100% ok with a rendezvous approach if those additional messages mean a single call to PVFS_sys_io - Real datatype I/O in ROMIO. Avery's code has been languishing in a branch for way too long, pending creation of a thourough ROMIO test suite. We have tested the PVFS_request_hindexed approach very well, but other PVFS request types have not been used nearly as often. ==rob -- Rob Latham Mathematics and Computer Science Division A215 0178 EA2D B059 8CDF Argonne National Lab, IL USA B29D F333 664A 4280 315B _______________________________________________ Pvfs2-developers mailing list [email protected] http://www.beowulf-underground.org/mailman/listinfo/pvfs2-developers
