From: Jeff Squyres (jsquyres_at_open-mpi.org)
Date: Wed Jul 27 2005 - 04:41:37 PDT
On Jul 26, 2005, at 5:01 PM, Paul H. Hargrove wrote:
> There is no support in current BLCR versions for either POSIX or
> Linux-native async I/O support. While this has nothing to do with
> whatever linker problems Jeff mentioned, it could be the cause of the
> problems you've been seeing.
I'm inferring from Pradeep's mail that there was an RPM that was
removed, but has now been replaced (LAM won't use libaio unless it
finds it during configure -- so it must have been there at some point
and then was later removed).
> How/when is async I/O used in LAM? Is there a simple way to disable
> it via ssi params?
It's used in ROMIO. There are currently no SSI params to remove its
use -- part of the problem is that the wrapper compilers add "-laio"
So it's not just a run-time switch to change ROMIO's behavior, it's a
compile-time decision (ROMIO makes a bunch of decisions and sets
#define's based on whether AIO is present or not) for both LAM and
ROMIO.
But this also explains why we rarely (never?) saw this problem in our
own testing -- the vast majority of our manual testing builds disable
ROMIO because it takes so long to compile. Urgh. This also explains
why my LAM build on Pradeep's system worked -- I configured and built
LAM after the libaio-devel RPM was removed, so my build did not add
-laio.
The quick and easy solution is to disable ROMIO ("--without-romio").
Not really an optimal solution, but it'll work.
--
{+} Jeff Squyres
{+} The Open MPI Project
{+} http://www.open-mpi.org/