How do I turn off hyperthreading on 6.0 ?

[Colin Percival]

Pete French wrote:
> I have:
> 
> websvr04# sysctl machdep.hlt_logical_cpus
> machdep.hlt_logical_cpus: 1
> 
> but I am still seeing 4 CPU's as I have two physical processors, each with
> two logical ones onboard.

The way machdep.hlt_logical_cpus works is by telling the scheduler to
ignore the extra logical processors, not by pretending that the extra
logical processors don't exist at all.  (This was necessary to ensure
that interrupts could still run on the extra threads -- otherwise some
problems appeared with broken BIOSes which couldn't route interrupts
correctly.)

If you look at top(1), which processors do you see actually running
processes?

Colin Percival