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Subject: Re: [OMPI devel] RFC: job size info in OPAL
From: Nathan Hjelm (hjelmn_at_[hidden])
Date: 2014-07-31 10:58:27


+2^10000000

This information is absolutely necessary at this point. If someone has a
better solution they can provide it as an alternative RFC. Until then
this is how it should be done... Otherwise we loose uGNI support on the
trunk. Because we ARE NOT going to remove the mailbox size optimization.

-Nathan

On Wed, Jul 30, 2014 at 10:00:18PM +0000, Jeff Squyres (jsquyres) wrote:
> WHAT: Should we make the job size (i.e., initial number of procs) available in OPAL?
>
> WHY: At least 2 BTLs are using this info (*more below)
>
> WHERE: usnic and ugni
>
> TIMEOUT: there's already been some inflammatory emails about this; let's discuss next Tuesday on the teleconf: Tue, 5 Aug 2014
>
> MORE DETAIL:
>
> This is an open question. We *have* the information at the time that the BTLs are initialized: do we allow that information to go down to OPAL?
>
> Ralph added this info down in OPAL in r32355, but George reverted it in r32361.
>
> Points for: YES, WE SHOULD
> +++ 2 BTLs were using it (usinc, ugni)
> +++ Other RTE job-related info are already in OPAL (num local ranks, local rank)
>
> Points for: NO, WE SHOULD NOT
> --- What exactly is this number (e.g., num currently-connected procs?), and when is it updated?
> --- We need to precisely delineate what belongs in OPAL vs. above-OPAL
>
> FWIW: here's how ompi_process_info.num_procs was used before the BTL move down to OPAL:
>
> - usnic: for a minor latency optimization / sizing of a shared receive buffer queue length, and for the initial size of a peer lookup hash
> - ugni: to determine the size of the per-peer buffers used for send/recv communication
>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
> For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
>
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> Link to this post: http://www.open-mpi.org/community/lists/devel/2014/07/15373.php



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