How do you detect that hyperthreading is activated?

How do you detect that hyperthreading is activated?

[Björn Antonsson]

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Hi,
I have an application that needs to check if a linux kernel has booted
with hyperthreading enabled on ia32, in order to do some special tweaks.
I know how you detect that a CPU supports hyperthreading, but how do you
detect that the kernel has booted with hyperthreading activated?

And by hyperthreading activated I mean that the current number of CPUs,
for example 8, are actually 4 physical CPUs and 4 logical CPUs.

Is there a way that I can get at the logical/physical CPU bits, as
reported by the CPUID instruction, of all available CPUs? Or is there
an even better way?

/Björn

Re: How do you detect that hyperthreading is activated?

[Dave Jones]

On Thu, May 30, 2002 at 05:29:40PM +0200, Björn Antonsson wrote:
 > Is there a way that I can get at the logical/physical CPU bits, as
 > reported by the CPUID instruction, of all available CPUs? Or is there
 > an even better way?

/dev/cpu/*/cpuid

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| Dave Jones.        http://www.codemonkey.org.uk
| SuSE Labs