Open MPI logo

Open MPI Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Development mailing list

Subject: Re: [OMPI devel] SM init failures
From: Tim Mattox (timattox_at_[hidden])
Date: 2009-03-30 13:40:27

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]
> _______________________________________________
> devel mailing list
> devel_at_[hidden]

Tim Mattox, Ph.D. -
 tmattox_at_[hidden] || timattox_at_[hidden]
    I'm a bright...