[MPI3-IO] I/O working group Notes

[Rob Latham]

On Wed, Mar 13, 2013 at 02:46:34PM -0500, Quincey Koziol wrote:
> > Can something be done with generalized request?
> 	Someone always brings this up.  :-)  We should get up to speed on the GRQ routines and know what they can do...

They cannot do much.  I am, reluctantly, the worlds expert on
generalized requests, having written a paper about it 5(!!!) years
ago.

http://dx.doi.org/10.1007/978-3-540-75416-9_33

pdf: http://www.mcs.anl.gov/~robl/papers/latham_grequest-enhance.pdf

Standard Generalized requests have a "all progress must happen outside
of MPI" progress model.  Perhaps in this modern surfeit of cores era,
it is no longer a big deal to spawn a thread ?

The paper I linked proposes generalized request extensions designed to
play better with posix, pvfs, and NTFS async i/o routines.  These
routines can make progress in the background, but do need someone to
call a completion function (aio_suspend, PVFS_sys_wait, or
WaitForMultipleObjectEx).

==rob

-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA