linux-kernel - Re: [PATCH 1/3] x86: introduce cpuinfo->cpu_node

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Date:	Wed, 6 May 2009 13:44:23 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andreas Herrmann <andreas.herrmann3@....com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] x86: introduce cpuinfo->cpu_node_id to reflect
	topology of multi-node CPU


* Andreas Herrmann <andreas.herrmann3@....com> wrote:

> Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
> ---
>  arch/x86/include/asm/processor.h |    2 ++
>  arch/x86/kernel/cpu/common.c     |    2 ++
>  arch/x86/kernel/cpu/proc.c       |    1 +
>  arch/x86/kernel/smpboot.c        |    5 ++++-
>  4 files changed, 9 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 0b2fab0..b49d72b 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -106,6 +106,8 @@ struct cpuinfo_x86 {
>  	u16			booted_cores;
>  	/* Physical processor id: */
>  	u16			phys_proc_id;
> +	/* Node id in case of multi-node processor: */
> +	u16			cpu_node_id;

btw., do you have any plans to propagate this information into the 
scheduler domains tree?

Another level of domains, to cover the two internal nodes, would do 
the trick nicely and automatically. This would work even if the BIOS 
does not provide information and we have to go to lowlevel registers 
or CPUID to recover it.

This can be done even if there's no SRAT. (there's no SRAT because 
say due to interleaving there's no real NUMA structure of memory. 
But there's still CPU scheduling differences worth expressing.)

	Ingo
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