linux-kernel - Re: nr_cpu_ids incorrect on AMD Quad-Core Opteron 8380

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Date:	Tue, 2 Feb 2010 13:49:06 +1300
From:	zhiyi <zhuang@...otago.ac.nz>
To:	Borislav Petkov <petkovbb@...glemail.com>
Cc:	linux-kernel@...r.kernel.org, Zhiyi Huang <hzy@...otago.ac.nz>,
	jkmair@...otago.ac.nz
Subject: Re: nr_cpu_ids incorrect on AMD Quad-Core Opteron 8380


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

> On Mon, Feb 1, 2010 at 2:57 PM, Borislav Petkov <petkovbb@...glemail.com 
> > wrote:
>> On Sun, Jan 31, 2010 at 11:59 PM, zhiyi <zhuang@...otago.ac.nz>  
>> 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@...otago.ac.nz
Phone: 0064-3-4795680
Fax: 0064-3-4798529

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