Bug 46001

Summary:	/proc/cpuinfo displays wrong core/siblings count for Intel Atom N270 CPU
Product:	Platform Specific/Hardware	Reporter:	Evangelos Foutras (evangelos)
Component:	i386	Assignee:	platform_i386
Status:	NEW ---
Severity:	normal	CC:	a.p.zijlstra, alan, arthur.titeica, geralt
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	3.5, 3.5.1, 3.7.2, 3.9	Subsystem:
Regression:	Yes	Bisected commit-id:
Attachments:	Diff of /proc/cpuinfo between Linux 3.4.8 and Linux 3.5.1

Description Evangelos Foutras 2012-08-15 05:12:59 UTC

/proc/cpuinfo on Linux 3.5 (and Linux 3.5.1) contains different values for cpu0's "siblings" and cpu1's "siblings" and "cpu cores", compared to the values seen on Linux 3.4.8 (and previous versions).

I came across a relevant-looking fix [1] but it's already included in Linux 3.5.x.

The CPU is an Intel Atom N270 [2] (1 core with Hyper-Threading).

[1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=ceb1cbac8eda66cf0f889def226b4e82f8ff857b
[2] http://ark.intel.com/products/36331/Intel-Atom-Processor-N270-%28512K-Cache-1_60-GHz-533-MHz-FSB%29

Comment 1 Evangelos Foutras 2012-08-15 05:41:09 UTC

Created attachment 77751 [details]
Diff of /proc/cpuinfo between Linux 3.4.8 and Linux 3.5.1

Comment 2 Alfredo Amatriain 2012-09-22 09:28:52 UTC

I'm experiencing the same bug with linux 3.5.3

Originally reported in the Arch bugtracker: 

https://bugs.archlinux.org/task/31606#comment99437