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

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Date:	Wed, 6 May 2009 18:14:40 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Ingo Molnar <mingo@...e.hu>
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

On Wed, May 06, 2009 at 01:44:23PM +0200, Ingo Molnar wrote:
> 
> * 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?

No plans yet -- as I don't know much about the scheduler code so far.
But it's worth it and I'll do it.

> 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.

Yes.

(And maybe for powersaving reasons it might be worth to use nodes on
same socket instead of nodes on different sockets. But I have to check
that in-depth first.)

> 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.)

Seconded.


Regards,
Andreas

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