Re: [PATCH 0/13] Time: Generic Timeofday Subsystem (v B10)

john stultz
2005-11-15T21:05:24Z

On Tue, 2005-11-15 at 21:53 +0100, Ingo Molnar wrote:
> * john stultz <johnstul@us.ibm.com> wrote:
>
> > > idle=poll does seem to fix the major clock drift problem. There may
> > > still be an issue, but it's much smaller:
> > >
> > > 2.6.14-mm2-todb10:
> > > 14 Nov 21:50:57 offset: -0.025373 drift: -22404.0 ppm
> > > 14 Nov 21:51:59 offset: -1.577053 drift: -24985.4603175 ppm
> > > 14 Nov 21:53:00 offset: -3.104569 drift: -25012.9032258 ppm
> > >
> > > 2.6.14-mm2-todb10 with idle=poll:
> > > 14 Nov 21:37:59 offset: 5.9e-05 drift: 63.0 ppm
> > > 14 Nov 21:39:00 offset: 0.003207 drift: 51.7903225806 ppm
> >
> > Hmm. It seems the c3 compensation is triggering when it shouldn't, or
> > maybe its over compensating.
> >
> > I can't reproduce it on my laptop. Do you recall if in previous tests
> > you saw anything like this? I'm trying to narrow down if its just a
> > difference in hardware or if something in the c3 idle code changed.
>
> it's with an earlier queue of yours, but maybe it's related: i have a
> report that HPET causes HRT inaccuracies (e.g. sleeps for 20 msecs last
> 21 msecs). If all HPET options are turned off in the .config then
> everything is fine and accurate.

Hmm. HPET would be separate from this, I believe. I suspect that could
be related to the HPET legacy replacement functionality, where the HPET
is triggering the timer interrupts. Not something I changed, but
probably should be looked into.

thanks
-john