[mpich-discuss] where is two-phase I/O implemented

[Rob Latham]

On Wed, May 01, 2013 at 11:41:52AM +0200, Matthieu Dorier wrote:
> Btw how does Mpich knows which ADIO backend to use, in general? (and
> more specifically how does ADIOI_GEN_ReadStridedColl knows that it
> has to use ADIOI_BGL_ReadContig?) Does it have something to do with
> the fact that for instance with PVFS2 when the kernel module is not
> used, the filename should be prefixed by pvfs2:// ? If I want to
> develop a new ADIO backend, how can I make it such that filenames
> prefixed with myfilesystem:// will use this backend? (Maybe there's
> a documentation for that somewhere?)

To add a bit upon what Dries answered

Yes, if you prefix the file name, ROMIO will parse that and select the
right set of function pointers.

ROMIO will also try to guess the file system type (usually with a
'statfs' call.)  See the functions in adio/common/ad_fstype.c.

It's a bit of a mess because on some platforms one calls statfs,
others one calls fstatfs, etc.  If you squint around the preprocessor
directives I hope it eventually makes sense.  Don't hesitate to ask me
questions -- it's probably the messiest part of ROMIO ...

==rob

> Thanks,
> 
> Matthieu
> 
> ----- Mail original -----
> > De: "Pavan Balaji" <balaji at mcs.anl.gov>
> > À: discuss at mpich.org
> > Cc: "Matthieu Dorier" <matthieu.dorier at irisa.fr>
> > Envoyé: Mardi 30 Avril 2013 18:01:11
> > Objet: Re: [mpich-discuss] where is two-phase I/O implemented
> > 
> > 
> > Please don't call it mpich3; it's just "mpich" :-).
> > 
> >  -- Pavan
> > 
> > On 04/30/2013 10:32 AM US Central Time, Matthieu Dorier wrote:
> > > Hi,
> > > 
> > > A question more for the mpich3 developers:
> > > 
> > > If I were to implement an ADIO interface to a file system in
> > > mpich3,
> > > would I have to implement optimizations like two-phase I/O myself
> > > or are
> > > these optimizations implemented outside ADIO, independently of the
> > > file
> > > system?
> > > 
> > > Thanks,
> > > 
> > > Matthieu Dorier
> > > PhD student at ENS Cachan Brittany and IRISA
> > > http://people.irisa.fr/Matthieu.Dorier
> > > 
> > > 
> > > _______________________________________________
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> > > 
> > 
> > --
> > Pavan Balaji
> > http://www.mcs.anl.gov/~balaji
> > 
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-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA