Re: [ck] [PATCH] dynamic-tick patch modified for SMP

Tony Lindgren
2005-08-17T07:53:49Z

* Con Kolivas <kernel@kolivas.org> [050816 06:23]:
> On Tue, 16 Aug 2005 23:19, Srivatsa Vaddagiri wrote:
> > On Tue, Aug 16, 2005 at 02:30:51AM +1000, Con Kolivas wrote:
> > > Time definitely was lost the longer the machine was running.
> >
> > I think I found the reason for time drift. Basically cur_timer->mark_offset
> > doesnt expect to be called from non-timer interrupt handler. Hence it drops
> > one jiffy from the lost count. I fixed this in some "crude" fashion and
> > time has not drifted so far or is pretty much close to what it was in
> > pre-smp version. Will find a neat way to fix this and post a patch soon.
> >
> > > You mean disable it at runtime or not compile it in at all? Disabling it
> > > at runtime caused what I described to you as PIT mode (long stalls etc).
> >
> > I think I have recreated this on a machine here. Disabling
> > CONFIG_DYN_TICK_APIC at compile-time didnt seem to make any difference.
> > Will look at this problem next.
>
> Excellent.
>
> Mind you the APIC dyntick never really worked well on the pre-smp version on
> any hardware I tried it on so if you get both the APIC and PIT version
> working well you're doing great.

Sounds good! I only got the APIC stuff working properly on P3, but not on P4.

Tony