[MPICH2-dev] RE: alignment hints for calculating the file domain.

[Yu, Weikuan]

Further update on this, attached is the working code I have in the Lustre ADIO driver.

The condition checking on "fd->file_system == ADIO_LUSTRE" can be removed for generic usage, assuming fs-specific ADIO saves a file's striping parameters in fd->info.

--
Weikuan Yu <+> 1-865-574-7990
http://ft.ornl.gov/~wyu/



-----Original Message-----
From: owner-mpich2-dev at mcs.anl.gov on behalf of Yu, Weikuan
Sent: Tue 7/10/2007 11:00 AM
To: Robert Latham
Cc: wangdi; mpich2-dev at mcs.anl.gov
Subject: RE: [MPICH2-dev] RE: alignment hints for calculating the file domain.
 
 

> -----Original Message-----
> From: Robert Latham [mailto:robl at mcs.anl.gov] 
> 
> On Tue, Jul 10, 2007 at 08:55:18AM -0400, Yu, Weikuan wrote:
> > Wangdi has observed a lot of lock contentions when the file domain 
> > partitions in collective IO are not aligned on Lustre 
> stripe boundary 
> > (say 1MB). As a remedy of that, we are proposing a minor 
> change on the 
> > implementation of ADIOI_GEN_Calc_file_domains() for it to 
> respect an 
> > advisory alignment. The attached patch illustrates what we are 
> > proposing.
> 
> Ok, so you turn fd_size from an output parameter to an in/out 
> parameter.  I don't think that's introducing noticeably more 
> complexity to the interface.  

Right, that's the intention. We want to avoid a new function which adds
very little to the existing one.

> 
> Before you call calc_file_domains, how will you set fd_size?  
> Through a hint the user can override? 

We can do that with a separate ADIO driver. For Lustre, we can find out
the stripe_size from the file attributes. Users can also suggest an hint
on stripe_size of new files. 

--Weikuan

> 
> > P.S.: We will use mpich-discuss at mcs.anl.gov for further 
> discussions if 
> > mpich2-dev is not for this purpose.
> 
> I think this list will be fine.
> 
> ==rob
> 
> --
> Rob Latham
> Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
> Argonne National Lab, IL USA                 B29D F333 664A 4280 315B
> 



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