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Subject: Re: [OMPI devel] SM init failures
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-03-30 13:50:24


It's half done, actually. But it was still going to be an option, not
necessarily the only way to do it:

     http://www.open-mpi.org/hg/hgwebdir.cgi/jsquyres/shm-sysv/

On Mar 30, 2009, at 1:40 PM, Tim Mattox wrote:

> I've been lurking on this conversation, and I am again left with the
> impression
> that the underlying shared memory configuration based on sharing a
> file
> is flawed. Why not use a System V shared memory segment without a
> backing file as I described in ticket #1320?
>
> On Mon, Mar 30, 2009 at 1:34 PM, George Bosilca
> <bosilca_at_[hidden]> wrote:
> > Then it looks like the safest solution is the use either ftruncate
> or the
> > lseek method and then touch the first byte of all memory pages.
> > Unfortunately, I see two problems with this. First, there is a clear
> > performance hit on the startup time. And second, we will have to
> find a
> > pretty smart way to do this or we will completely break the memory
> affinity
> > stuff.
> >
> > george.
> >
> > On Mar 30, 2009, at 13:24 , Iain Bason wrote:
> >
> >>
> >> On Mar 30, 2009, at 12:05 PM, Jeff Squyres wrote:
> >>
> >>> But don't we need the whole area to be zero filled?
> >>
> >> It will be zero-filled on demand using the lseek/touch method.
> However,
> >> the OS may not reserve space for the skipped pages or disk
> blocks. Thus one
> >> could still get out of memory or file system full errors at
> arbitrary
> >> points. Presumably one could also get segfaults from an mmap'ed
> segment
> >> whose pages couldn't be allocated when the demand came.
> >>
> >> Iain
> >>
> >> _______________________________________________
> >> devel mailing list
> >> devel_at_[hidden]
> >> http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >
> > _______________________________________________
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >
>
>
>
> --
> Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/
> tmattox_at_[hidden] || timattox_at_[hidden]
> I'm a bright... http://www.the-brights.net/
>
> _______________________________________________
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> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel

-- 
Jeff Squyres
Cisco Systems