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Subject: Re: [hwloc-devel] new version of docs
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2010-06-25 12:58:08

On Jun 25, 2010, at 12:53 PM, Jeff Squyres (jsquyres) wrote:

> > I'm uneasy with “PU#15, for example, changes location from NUMA node
> > #0 to #1.” The location doesn't have really changed, PUs have just
> > been renumbered.

How's this:

Notice that hwloc only sees half the PUs when SMT is disabled. PU#15,
for example, seems to change location from NUMA node #0 to #1. In
reality, no PU's "moved" -- they were simply re-numbered when hwloc
only saw half as many. Hence, PU#15 in the SMT-disabled picture
probably corresponds to PU#30 in the SMT-enabled picture.

This same "PUs have disappeared" effect can be seen on other platforms
-- even platforms / OSs that provide much more information than the
above PPC64 system. This is an unfortunate side-effect of how
operating systems report information to hwloc.

Jeff Squyres
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