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SubjectRe: detecting hyperthreading in linux 2.4.19
> > Is there a way for a userspace program running on linux 2.4.19 to tell
> > the difference between a single hyperthreaded xeon P4 with HT enabled
> > and a dual hyperthreaded xeon P4 with HT disabled? The /proc/cpuinfos
> > for the two cases are indistinguishable.
> I don't know of any way to do this in userland. The whole point is that the
> sibling processors are supposed to look like real ones.
> You _could_ try running two processes simultaneously in tight spin loops for
> 100 million cycles and comparing the amount of real time consumed. That
> would be rather unreliable and kludgey though.

If /proc/interrupts shows a processor is handling interrupts then it
is definitely a 'real' one. If it isn't handling interrupts, it may
or may not be a 'real' one. That's another unreliable and kludgey way
to tell the difference :-).

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