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SubjectRe: [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@amd.com> wrote:
>
> > Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.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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