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Subject: Re: [OMPI devel] SM init failures
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-03-30 12:05:03


But don't we need the whole area to be zero filled?

On Mar 28, 2009, at 5:02 PM, George Bosilca wrote:

> It is way to expensive to write the whole file. That's why I proposed
> to only write the last byte. This will force the OS to really map the
> file on the systems less POSIX compliant.
>
> george.
>
> On Mar 28, 2009, at 13:50 , Jeff Squyres wrote:
>
> > How about just write()ing a bunch of 0's instead of using ftruncate?
> >
> > On Mar 27, 2009, at 11:09 PM, Eugene Loh wrote:
> >
> >> Paul H. Hargrove wrote:
> >>
> >> > Quoting from a different manpage for ftruncate:
> >> > [T]he POSIX standard allows two behaviours for ftruncate
> >> > when length exceeds the file length [...]: either
> >> returning an
> >> > error, or
> >> > extending the file.
> >> > So, if that is to be trusted, it is not legal by POSIX to
> >> *silently*
> >> > not extend the file.
> >>
> >> On a Solaris system, the ftruncate man page says:
> >>
> >> truncate, ftruncate - set a file to a specified length
> >>
> >> The truncate() function causes the regular file named by
> >> path to have a size equal to length bytes.
> >>
> >> If the file previously was larger than length, the extra
> >> data is discarded. If the file was previously shorter than
> >> length, its size is increased, and the extended area appears
> >> as if it were zero-filled.
> >>
> >> So, the sense is not of "truncating" (shortening) per se, but of
> >> fixing
> >> a new length, whether that length is longer or shorter.
> >>
> >> I guess we could try to track down the ftruncate behavior on the
> >> systems
> >> in question, but (IMHO) this doesn't feel like the correct
> >> explanation.
> >> _______________________________________________
> >> devel mailing list
> >> devel_at_[hidden]
> >> http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >
> >
> > --
> > Jeff Squyres
> > Cisco Systems
> >
> > _______________________________________________
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
> _______________________________________________
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-- 
Jeff Squyres
Cisco Systems