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Subject: Re: [OMPI devel] System V Shared Memory for Open MPI: Request forCommunity Input and Testing
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2010-06-11 07:10:48


On Jun 11, 2010, at 5:43 AM, Paul H. Hargrove wrote:

> > Interesting. Do you think this behavior of the linux kernel would
> > change if the file was unlink()ed after attach ?
>
> As Jeff pointed out, the file IS unlinked by Open MPI, presumably to
> ensure it is not left behind in case of abnormal termination.

I have to admit that I lied. :-(

Sam and I were talking on the phone yesterday about the shm_open() stuff and to my chagrin, I discovered that the mmap'ed files are *not* unlinked in OMPI until MPI_FINALIZE. I'm not actually sure why; I could have sworn that we unlinked them after everyone mmap'ed them...

Regardless, Sam and I made good progress on the shm_open() stuff yesterday. We should have something for Sylvain to test soon. I believe that Sam is looking for the right place to put the shm_unlink() step so that we *don't* leave it around like we do with the mmap files. I have a few more steps to do to add in the right silent-failover stuff, but we'll probably have something for Sylvain to test soon (final polish may be delayed a little because I'm on travel to the MPI Forum next week).

-- 
Jeff Squyres
jsquyres_at_[hidden]
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