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Subject: Re: [OMPI users] memalign usage in OpenMPI and it's consequencesfor TotalVIew
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-10-01 13:58:24


Did that make it over to the v1.3 branch?

On Oct 1, 2009, at 1:39 PM, Samuel K. Gutierrez wrote:

> Hi,
>
> I think Jeff has already addressed this problem.
>
> https://svn.open-mpi.org/trac/ompi/changeset/21744
>
> --
> Samuel K. Gutierrez
> Los Alamos National Laboratory
>
> On Oct 1, 2009, at 11:25 AM, Peter Thompson wrote:
>
> > We had a question from a user who had turned on memory debugging in
> > TotalView and experience a memory event error Invalid memory
> > alignment request. Having a 1.3.3 build of OpenMPI handy, I tested
> > it and sure enough, saw the error. I traced it down to, surprise, a
> > call to memalign. I find there are a few places where memalign is
> > called, but the one I think I was dealing with was from malloc.c in
> > ompi/mca//io/romio/romio/adio/common in the following lines:
> >
> >
> > #ifdef ROMIO_XFS
> > new = (void *) memalign(XFS_MEMALIGN, size);
> > #else
> > new = (void *) malloc(size);
> > #endif
> >
> > I searched, but couldn't find a value for XFS_MEMALIGN, so maybe it
> > was from opal_pt_malloc2_component.c instead, where the call is
> >
> > p = memalign(1, 1024 * 1024);
> >
> > There are only 10 to 12 references to memalign in the code that I
> > can see, so it shouldn't be too hard to find. What I can tell you
> > is that the value that TotalView saw for alignment, the first arg,
> > was 1, and the second, the size, was 0x100000, which is probably
> > right for 1024 squared.
> >
> > The man page for memalign says that the first argument is the
> > alignment that the allocated memory use, and it must be a power of
> > two. The second is the length you want allocated. One could argue
> > that 1 is a power of two, but it seems a bit specious to me, and
> > TotalView's memory debugger certainly objects to it. Can anyone tell
> > me what the intent here is, and whether the memalign alignment
> > argument is thought to be valid? Or is this a bug (that might not
> > affect anyone other than TotalView memory debug users?)
> >
> > Thanks,
> > Peter Thompson
> > _______________________________________________
> > users mailing list
> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>
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-- 
Jeff Squyres
jsquyres_at_[hidden]