Re: detecting hyperthreading in linux 2.4.19

From: Mikael Pettersson (mikpe@csd.uu.se)
Date: Fri Jan 10 2003 - 06:19:07 EST


Dave Jones writes:
> On Fri, Jan 10, 2003 at 08:05:07AM +0100, Mikael Pettersson wrote:
>
> > If the kernel has sched_setaffinity() or some other way of binding a process
> > to a given CPU (as numbered by the kernel, which may or may not be related
> > to any physical CPU numbers), then this will do it: execute CPUID on each
> > CPU and check the initial APIC ID field. If you find one that's non-zero,
> > then HT is enabled.
>
> That's a horrible way of reimplementing /dev/cpu/x/cpuid 8-)

True. I forgot about that interface since I personally never configure or use it.

So this answers the original question. Just access /dev/cpu/$CPU/cpuid
for all (accessible) values of $CPU.
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