linux-kernel - Re: How to detect multi-core and/or HT-enabled CPUs in 2.4.x and 2.6.x kernels

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Date:	Wed, 27 Dec 2006 15:37:01 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Martin Knoblauch <knobi@...bisoft.de>
cc:	linux-kernel@...r.kernel.org
Subject: Re: How to detect multi-core and/or HT-enabled CPUs in 2.4.x and
 2.6.x kernels


On Dec 27 2006 06:16, Martin Knoblauch wrote:
>
> So far it seems that looking at the "physical id", "core id" and "cpu
>cores" of /proc/cpuinfo is the way to go.

Possibly, but it does not catch all cases. 

$grep '"physical id' /erk/kernel/linux-2.6.20-rc2/ -r

returns exactly three lines, for 
/erk/kernel/linux-2.6.20-rc2/arch/i386/kernel/cpu/proc.c 
/erk/kernel/linux-2.6.20-rc2/arch/ia64/kernel/setup.c 
/erk/kernel/linux-2.6.20-rc2/arch/x86_64/kernel/setup.c

So what'cha doing about, say, sparc64? Here is its procinfo of a 
standard SMP one:

15:31 ares:~ # cat /proc/cpuinfo
cpu             : TI UltraSparc II  (BlackBird)
fpu             : UltraSparc II integrated FPU
prom            : OBP 3.30.0 2003/11/11 10:37
type            : sun4u
ncpus probed    : 2
ncpus active    : 2
D$ parity tl1   : 0
I$ parity tl1   : 0
Cpu0Bogo        : 800.49
Cpu0ClkTck      : 0000000017d78400
Cpu1Bogo        : 800.05
Cpu1ClkTck      : 0000000017d78400
MMU Type        : Spitfire
State:
CPU0:           online
CPU1:           online


> In 2.6 I would try to find the  distinct "physical id"s and  and sum
>up the corresponding "cpu cores". The question is whether this would
>work for 2.4 based systems.
>
> Does anybody recall when the "physical id", "core id" and "cpu cores"
>were added to /proc/cpuinfo ?

Why don't you check it out? 2.4.34 only has the "physical id" string for 
x86_64. It does not seem to have CONFIG_SCHED_SMT at all. (Time to leave 
the dead horse alone.)


	-`J'
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