linux-kernel - Re: [PATCH 0/5 v4] x86: Adapt CPU topology detection for AMD Magny-Cours

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Message-ID: <4A79EA5A.7040308@inria.fr>
Date:	Wed, 05 Aug 2009 22:23:54 +0200
From:	Brice Goglin <Brice.Goglin@...ia.fr>
To:	Andreas Herrmann <andreas.herrmann3@....com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Borislav Petkov <borislav.petkov@....com>
Subject: Re: [PATCH 0/5 v4] x86: Adapt CPU topology detection for AMD Magny-Cours

Andreas Herrmann wrote:
> Changes to previous patch set:
> - fixed allnoconfig compile error and link error if CONFIG_PCI=n
> - fixed hotplug issue: cpumask of siblings sharing same L3 were not
>   properly updated
> - properly allocate cpu_node_map
>
> Current patch set contains 5 patches:
> - patch 1 adapts common code to show cpu_node_id,
>   cpu_node_siblings and cpu_node_siblings_list in
>   /sys/devices/system/cpu/cpu*/topology
> - patch 2 prepares arch/x86 to provide cpu_node information
> - patch 3 sets up cpu_node information for AMD Magny-Cours CPU
> - patch 4 fixes L3 cache information for Magny-Cours
> - patch 5 fixes mcheck code for Magny-Cours
>   

Hello Andreas,

Reading your first submission I find something disturbing. You say that
we'll have the following sibling information:

  Level        | Set of CPUs
 --------------|---------------
  phys_package | core_siblings
  cpu_node     | cpu_node_siblings
  core         | thread_siblings
  thread       | one CPU


This breaks the existing convention/semantics. Currently
core/thread_siblings contains the cpumask covering *all* siblings of
current core/thread object. What you're adding only shows the cpumask of
current "cpu_node" object in cpu_node_siblings. I don't have any
preference between both semantics, but I think "cpu_node" should use the
semantics that "core" and "thread" do. So the above should be changed into:

  Level        | Set of CPUs
 --------------|---------------
  phys_package | cpu_node_siblings
  cpu_node     | core_siblings
  core         | thread_siblings
  thread       | one CPU


Brice

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