Re: detecting hyperthreading in linux 2.4.19

[Mikael Pettersson]

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.