linux-kernel - Re: [PATCH] x86: Consider multiple nodes in a single socket to be "sane"

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Message-ID: <20140916100725.GB4796@osiris>
Date:	Tue, 16 Sep 2014 12:07:25 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Dave Hansen <dave@...1.net>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, mingo@...nel.org,
	hpa@...ux.intel.com, ak@...ux.intel.com,
	Alex Chiang <achiang@...com>, Borislav Petkov <bp@...e.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mike Travis <travis@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] x86: Consider multiple nodes in a single socket to be
 "sane"

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.

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