Definition of "siblings" in /proc/cpuinfo Post: 302381958

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Top Forums UNIX for Dummies Questions & Answers Definition of "siblings" in /proc/cpuinfo Post 302381958 by treesloth on Monday 21st of December 2009 02:37:51 PM

12-21-2009

Registered User

Definition of "siblings" in /proc/cpuinfo

So, I'm looking over /proc/cpuinfo and have a question... I've read that "siblings" refers to hyperthreading, but that seems odd considering the contents of cpuinfo. Here's a part:

Code:

model name      : Intel(R) Xeon(R) CPU           E5410  @ 2.33GHz
physical id     : 0
siblings        : 4
core id         : 0
cpu cores       : 4

That almost seems to say that the CPU is a quad-core Xeon (which is correct) as well as being hyperthreaded-- each core having 4 hyperthreads. That seems wrong, though. It seems more likely that it's saying that the CPU has 4 cores and 4 hyperthreads total-- that is, depending on how one looks at it, one hyperthread per core, or, alternatively, 4 cores and no hyperthreading. Four hyperthreads per core would instead be:

Code:

siblings        : 4
cpu cores       : 16

Am I understanding this correctly? For that matter, is there a definitive publication about this? I've looked for it, and will continue, but no luck so far...

treesloth

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LEARN ABOUT LINUX

lscpu

LSCPU(1)							   User Manuals 							  LSCPU(1)

NAME

       lscpu - CPU architecture information helper

SYNOPSIS

       lscpu [-hpx] [-s directory]

DESCRIPTION

       lscpu gathers CPU architecture information like number of CPUs, threads, cores, sockets, NUMA nodes, information about CPU caches, CPU fam-
       ily, model, bogoMIPS, byte order and stepping from sysfs and /proc/cpuinfo, and prints it in a human-readable  format.	It  supports  both
       online  and  offline  CPUs.  It can also print out in a parsable format, including how different caches are shared by different CPUs, which
       can be fed to other programs.

OPTIONS

       -h, --help
	      Print a help message.

       -p, --parse
	      Print out in parsable instead of human-readable format.

       -s, --sysroot directory
	      Use the specified directory as system root.  This allows you to inspect a snapshot from a different system.

       -x, --hex
	      Use hexadecimal masks for CPU sets (e.g. 0x3).  The default is to print the sets in list format (e.g. 0,1).

BUGS

       The basic overview about CPU family, model, etc. is always based on the first CPU only.

       Sometimes in Xen Dom0 the kernel reports wrong data.

AUTHOR

       Cai Qian <qcai@redhat.com>
       Karel Zak <kzak@redhat.com>

AVAILABILITY

       The lscpu command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

Linux								   February 2011							  LSCPU(1)