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Subject: Re: [hwloc-users] Thread core affinity
From: Samuel Thibault (samuel.thibault_at_[hidden])
Date: 2011-08-04 11:01:04


Gabriele Fatigati, le Thu 04 Aug 2011 16:56:22 +0200, a écrit :
> L#0 and L#1 are physically near because hwloc consider shared caches map when
> build topology?

Yes. That's the whole point of sorting objects topologically first, and
numbering them afterwards. See the glossary entry for "logical index":

“The ordering is based on topology first, and then on OS CPU numbers”

I.e. OS CPU numbers are only used when no topology information (shared
cache etc.) provides any better sorting.

> Because if not, i don't know how hwloc understand the physical
> proximity of cores :(

Physical proximity of cores does not mean logical proximity. cores can
be next one to the other, and still share no cache at all. Forget the
expression "physical proximity", it does not provide any interesting
information. What matters is logical proximity. And that's *precisely*
what logical indexes express.

Samuel