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Date: Tue, 16 Sep 2014 12:07:25 +0200
From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Dave Hansen <dave@sr71.net>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH] x86: Consider multiple nodes in a single socket to be
 "sane"
Message-ID: <20140916100725.GB4796@osiris>
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On Tue, Sep 16, 2014 at 01:17:44AM -0700, Dave Hansen wrote:
> >> The sysfs effects here cause an issue with the hwloc tool where
> >> it gets confused and thinks there are more sockets than are
> >> physically present.
> > 
> > Meh, so then we need another mask.
> 
> s390 has this concept of a "book" although it's not obvious at all where
> this fits in to the hierarchy to me.  The help text and comments are
> pretty funny:
> 
> 	Book scheduler support improves the CPU scheduler's decision
> 	making when dealing with machines that have several books.
> 
> Wow, really?  Book scheduling helps with books?  I would have never
> guessed.

I'm glad the help text did enlighten you.

>  Wish I knew what a book was. :)  Google helped a bit:
> 	http://sysmagazine.com/posts/150430/
> but it's still not clear.  I think a book is below a node?
> 
> 	SMT <= LLC <= MC <= BOOK <= NODE

This one is correct. s390 does not have NUMA support. So we have one
node with multiple books.