From: Paul H. Hargrove (PHHargrove_at_lbl_dot_gov)
Date: Wed Jul 27 2005 - 10:21:00 PDT
Jeff,
I am not sure this explains why a simple hello world program should
fail to restart. Even if romio runs some initialization code at
MPI_Init time, I can see how any actual async I/O would be started.
-Paul
Jeff Squyres wrote:
> 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.
>
--
Paul H. Hargrove PHHargrove_at_lbl_dot_gov
Future Technologies Group
HPC Research Department Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory Fax: +1-510-486-6900