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Subject: Re: [OMPI devel] System V Shared Memory for Open MPI:Request for Community Input and Testing
From: N.M. Maclaren (nmm1_at_[hidden])
Date: 2010-05-04 06:36:28


On May 4 2010, Terry Dontje wrote:
>
>Is a configure-time test good enough? For example, are all Linuxes the
>same in this regard. That is if you built OMPI on RH and it configured
>in the new SysV SM will those bits actually run on other Linux systems
>correctly? I think Jeff had hinted to this similarly when suggesting
>this may need to be a runtime test.

A very good question. It is clearly NOT good enough for the affinity
problems I mentioned, because they are changeable by system configuration,
but this is more basic. I don't remember seeing any parameters to change
the behaviour of System V shared memory, as distinct from its constants.

Five years ago, I would have guessed "no", because this is exactly the
sort of area where the single-CPU and multi-CPU kernels differed, but
I believe that there is less of that sort of thing nowadays. However,
it's worth watching out for.

Regards,
Nick Maclaren.