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

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Message-ID: <20140918073224.GC24842@nazgul.tnic>
Date:	Thu, 18 Sep 2014 09:32:24 +0200
From:	Borislav Petkov <bp@...en8.de>
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>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH] x86: Consider multiple nodes in a single socket to be
 "sane"

On Wed, Sep 17, 2014 at 02:55:26PM +0200, Borislav Petkov wrote:
> This sounds misleading to me. If I would have to explain how I
> understand physical_package_id, I'd say it is the physical piece of
> silicon containing the core. Which is consistent with what Peter says
> that using it to identify NUMA nodes is wrong.
> 
> Btw, I'm trying to get on an AMD MCM box to dump those fields but it is
> kinda hard currently. Will report back once I have something...

Ok, so Brice sent me some AMD MCM data from a 4-socket box.
physical_package_id there really denotes the physical package, i.e.
silicon, i.e. physical socket which contains a core.

So on a 4-socket, 16 cores on each machine, you have:

	   physical_package_id
cpu0-15 :  0
cpu16-31:  1
cpu32-47:  2
cpu48-63:  3

which all looks nicely regular and clean.

core_siblings mirrors exactly that too, so you don't see the internal
nodes from that either, i.e:

cpu0/topology/core_siblings_list:0-15
...
cpu16/topology/core_siblings_list:16-31
...
cpu32/topology/core_siblings_list:32-47
...
cpu50/topology/core_siblings_list:48-63

-- 
Regards/Gruss,
    Boris.
--
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