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Subject: Re: [hwloc-devel] Fwd: BGQ empty topology with MPI
From: Christopher Samuel (samuel_at_[hidden])
Date: 2012-03-25 23:24:41


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On 25/03/12 17:43, Brice Goglin wrote:

> But it'd be good to understand what's going on in /sys on this
> machine. And I still don't understand why MPI changes things here.

My guess (looking at the BG/P CNK kernel code) is that /sys is not
present on a BG/Q compute node, only on its I/O nodes (which run a
Linux kernel), and so the code is only picking them up when the I/O is
being redirected via an I/O node (i.e. when MPI is in play).

Now I'd have thought that would happen with or without MPI, but who
knows..

cheers,
Chris
- --
    Christopher Samuel - Senior Systems Administrator
 VLSCI - Victorian Life Sciences Computation Initiative
 Email: samuel_at_[hidden] Phone: +61 (0)3 903 55545
         http://www.vlsci.unimelb.edu.au/

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