John Baldwin writes:
>
> On 01-May-2002 Andrew Gallatin wrote:
> >
> >
> > Can somebody remind me why we do not hlt in the idle loop on MP x86s?
> > Is this because a HLTed CPU is not going to notice a new runnable job
> > (possibly migrating from another CPU) until it gets an interrupt to
> > wake it up?
>
> Yes.
This seems to be an acceptable "loss" in performance in environments
where cooling is a concern. Is there a deadlock danger? Or is it
just a performance tweak to not HLT SMPs? Would you object to making
it a sysctl (machdep.smp_idle_hlt)?
> > Do both CPUs get clock interrupts on x86?
>
> No, the interrupts seem to be round-robin, but each clock intr is only
> sent to one CPU unlike on alpha where they are broadcast.
So each CPU gets (1/num_cpu) * hz clock interrupts/sec?
Drew
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