Thanks Rob. Good to know that it's the messiest part, I managed to find everything I need so I'm confident with the rest of ROMIO :) Matthieu ----- Mail original -----

De: "Rob Latham" <[email protected]> À: [email protected] Envoyé: Lundi 6 Mai 2013 17:38:11 Objet: Re: [mpich-discuss] where is two-phase I/O implemented

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" <[email protected]> À: [email protected] Cc: "Matthieu Dorier" <[email protected]> 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 _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss