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

Con Kolivas
2005-08-16T13:24:55Z

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.

Thanks!
Con