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

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Date:	Thu, 6 Aug 2009 18:08:35 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Brice Goglin <Brice.Goglin@...ia.fr>
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

On Thu, Aug 06, 2009 at 02:25:19PM +0200, Brice Goglin wrote:
> Andreas Herrmann wrote:
> > Of course I thought also to implement it this way because it looks
> > more consistent, but IMHO the patches are less intrusive if this
> > scheme is _not_ used. Instead I kept core_siblings as is ("for
> > historic reasons", nobody needs to accustom to new semantics). And use
> > cpu_node_siblings where it really matters.
> >   
> 
> Well, core_siblings and cpu_node_sibling will only be different on
> Magny-Cours anyway. So even if core_siblings becomes "all cores in
> cpu_node" instead of "all cores in socket", it won't actually break any
> existing setup. I personally prefer having the same kind of semantics
> for all foo_siblings rather than having something with a different
> meaning between core and thread.

You just want to have the user interface adapted to your
semantics. I.e. you want to have following attributes:
(from Documentation/cputopology.txt)

 1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
 represent the physical package id of  cpu X;
 2) /sys/devices/system/cpu/cpuX/topology/core_id:
 represent the cpu core id to cpu X;
 3) /sys/devices/system/cpu/cpuX/topology/cpu_node_id:
 represent the processor internal node_id to cpu X;
 4) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
 represent the thread siblings to cpu X in the same core;
 5) /sys/devices/system/cpu/cpuX/topology/core_siblings:
 represent the thread siblings to cpu X in the same processor internal node;
 6) /sys/devices/system/cpu/cpuX/topology/cpu_node_siblings:
 represent the thread siblings to cpu X in the same physical package;

 Note: In case of multi-node processors (e.g. Magny-Cours) 5 and 6
 differ. For all other CPUs 5 and 6 provide similar values and
 cpu_node_id is 0.

Ok, I can modify the first two patches accordingly to swap the two
attributes and also provide an update for the documentation file.

(But I will keep the internal identifiers for the cpu_node stuff
as is.)


Thanks,
Andreas

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