Re: [PATCHSET] Announce: High-res timers, tickless/dyntick and dynamic HZ -V4

Thomas Gleixner
2006-06-23T08:25:46Z

On Thu, 2006-06-22 at 21:31 -0600, Robert Hancock wrote:
> Thomas Gleixner wrote:
> > An updated patchset is available from:
> >
> > http://www.tglx.de/projects/hrtimers/2.6.17/patch-2.6.17-hrt-dyntick4.patch
>
> On my Compaq Presario X1050 laptop running Fedora Core 5 I get:
>
> 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.

Solution: Either use an UP kernel, or enable Local APIC in the BIOS (is
not possible in most BIOSes), or add "lapic" to the kernel command line.

Also for an UP kernel adding "lapic" to the commandline is good, as the
APIC is faster accessible than the PIT.

tglx