Re: [suse-amd64] False "lost ticks" on dual-Opteron system (=> timer twice as fast)

From: Andi Kleen
Date: Tue May 10 2005 - 08:09:01 EST


On Tue, May 10, 2005 at 01:54:53PM +0200, Bernd Paysan wrote:
> On Tuesday 10 May 2005 13:12, Andi Kleen wrote:
> > > So that explains why nobody sees this problem. But the TSC-based
> > > fallback timekeeping is still broken on SMP systems with PowerNow and
> > > distributed IRQ handling, which both together seem to be rare enough
> > > ;-).
> >
> > There is a patch pending for the TSC problem - using the pmtimer instead
> > in this case.
> >
> > But the distributed timer interrupt problem is weird. It should not
> > happen. You sure it was IRQ 0 that was duplicated and not "LOC" ?
>
> Yes. Only one CPU actually gets and handles the timer interrupt, but which
> one is somewhat random (for about 10 seconds, it's the same CPU, then it
> switches over).

That could be irqbalance doing its thing. Does it go away when
you stop it?

-Andi

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