* Thomas Gleixner <[email protected]> wrote:
> > Disabling NO_HZ and high resolution timers due to timer broadcasting
> >
> > Not sure exactly what this is indicating or what's triggered this, but
> > I'm assuming the patch isn't doing much on this machine?
>
> The system is configured for SMP, but this is an UP machine and the
> APIC is disabled in the BIOS. Linux uses then the PIT and an IPI
> mechanism to broadcast timer events. We need to do the event
> reprogramming per CPU, so we switch off in that situation.
hm, we should update the message to be less cryptic. Something like:
'Disabling NO_HZ and high resolution timers due to no APIC'
and in this particular case we should also finetune the condition a bit
and make it conditional on the number of CPUs. I.e. if someone boots an
SMP kernel on a UP box we should still allow the PIT. (there wont be any
broadcasting done) [the only exception would be if CONFIG_HOTPLUG_CPU is
specified - in that case we cannot be sure whether a new CPU will be
plugged in or not]
Ingo
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