Re: nr_cpu_ids incorrect on AMD Quad-Core Opteron 8380

From: zhiyi
Date: Mon Feb 01 2010 - 19:49:15 EST



On 2/02/2010, at 4:04 AM, Borislav Petkov wrote:

On Mon, Feb 1, 2010 at 2:57 PM, Borislav Petkov <petkovbb@xxxxxxxxxxxxxx > wrote:
On Sun, Jan 31, 2010 at 11:59 PM, zhiyi <zhuang@xxxxxxxxxxxxxx> wrote:
My module worked for a kernel 2.6.29 with CONFIG_NR_CPUS=64 on my dual
quad-core AMD Opteron. The value of nr_cpu_ids I got from the same module
was correct (8).

This could mean that your include/generated/autoconf.h, which is used by
external modules, is not updated and contains CONFIG_NR_CPUS=8. Do

make mrproper

in your kernel directory by moving your .config out of the way first and
then rebuild your kernel and external module(s). nr_cpu_ids should pick
up the updated CONFIG_NR_CPUS value from your .config.

That's actually not necessary - the nr_cpu_ids thing is set at compile
time to CONFIG_NR_CPUS but then capped to a possibly lower value upon
boot depending on the info in the ACPI mptables. Can you please send the
.config and the full dmesg of the quadsocket machine?

The dmesg relevant to nr_cpu_ids of the quad socket is:

[ 0.000000] NR_CPUS:64 nr_cpumask_bits:64 nr_cpu_ids:32 nr_node_ids:4

For comparison purposes, the dmesg for the dual socket is:

[ 0.000000] NR_CPUS:64 nr_cpumask_bits:64 nr_cpu_ids:8 nr_node_ids:1

It seems nr_node_ids:1 for the dual socket is not quite right though.

Cheers,
Zhiyi






Thanks.

--
Regards/Gruss,
Boris


=======================
Zhiyi Huang
Dept of Computer Science
University of Otago
Email: hzy@xxxxxxxxxxxxxx
Phone: 0064-3-4795680
Fax: 0064-3-4798529

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