linux-kernel - 2.6.32.1 kernel unable to use more than 2 of 16 CPUs on Intel E5540 (i7)

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Date:	Thu, 24 Jun 2010 16:45:13 -0500
From:	Kurt Newman <knewman@...baldataguard.com>
To:	linux-kernel@...r.kernel.org
Subject: 2.6.32.1 kernel unable to use more than 2 of 16 CPUs on Intel E5540
 (i7)

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I'm posting here to get a bit of help to figure out this issue, or find
advice on a better mailing list or location to post this question.

The linux-smp and linux-config lists don't get many posts, while
linux-admin hasn't yielded much (perceived) help.

- ------------------------

My problem and question is:

I've tried 2.6.31.13 and 2.6.32.1, but none of these compilations find
all 16 CPUs on this E5540 (2 cpus, 4 cores each, 2 HT threads each).
However, using these same custom kernels on an Intel 5130, shows all 4
"cpus" (2 cpus, 2 cores each, no HT).  I've also tried older kernels
from common distros that find all 16 cpus just fine.  I'm guessing they
patched in support for additional hardware.

Q: What am I doing wrong, that prevents this kernel from seeing all
CPUs?  Or, could someone point me in the right direction?

- ------------------------

Relevant background information:

1) I am limited to a 32-bit OS and an older kernel because of some
software limitations.

2) While I've enabled CONFIG_HOTPLUG_CPU, I've confirmed that I'm not
passing any kernel args that would limit what is used (e.g. maxcpus=).

3) From the things I've looked at (e.g. /sys), the kernel seems to know
that there's 16 CPUs, but will only use 2.

4) I'm attaching my kernel config, dmesg output, /sys output, and
/proc/cpuinfo output to help.  NOTE: I've tried using CONFIG_MCORE2 and
CONFIG_M686, neither of these changes anything.

Thank you for your time,
Kurt

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Download attachment "config-2.6.32.1_GDG01.gz" of type "application/x-gzip" (15245 bytes)

Download attachment "cpuinfo-2.6.32.1_GDG01.gz" of type "application/x-gzip" (597 bytes)

Download attachment "dmesg-2.6.32.1_GDG01.gz" of type "application/x-gzip" (15086 bytes)

Download attachment "sys-devices-2.6.32.1_GDG01.gz" of type "application/x-gzip" (191 bytes)