Re: 2.6.17-mm2 hrtimer code wedges at boot?

[john stultz <johnstul@us.ibm.com>]

On Thu, 2006-07-06 at 02:37 +0200, Roman Zippel wrote:
> Hi,
> 
> On Wed, 5 Jul 2006, Valdis.Kletnieks@vt.edu wrote:
> > [   29.528533] Time: tsc clocksource has been installed.
> > [   29.552855] clock changed at -296333 (4294314460971008)
> > [   29.577109] clock tsc: m:2628985,s:22,cl:47171945132,ci:1595166,xn:0,xi:4193667486510,e:0
> > [   29.601869] big adj at -296332 (4294314460971008,-16,-25522656,-11031712)
> > [   29.626688] clock tsc: m:2628985,s:22,cl:47288392250,ci:1595166,xn:148610636380190,xi:4193667486510,e:-76300711936
> > [   29.652263] big adj at -296331 (4294314460971008,512,816724992,737704960)
> > [   29.677968] clock tsc: m:2628969,s:22,cl:47368150550,ci:1595166,xn:358292745604602,xi:4193641963854,e:1193037240320
> 
> Ok, I see now the problem, the last cycle value is always at least 50 
> times incremented between adjustments and that also means any error 
> adjustment is applied at least 50 times, which quickly gets out of 
> control.
> Is it possible that your console output is really slow? Otherwise I can't 
> explain these numbers, everything looks initialized fine for a 1.6GHz 
> clock, but it seems to take ages to print a single line.

Dang! You beat me to the analysis :)  I think we're on the same page
here.


> I have to run some tests and later this week there should be a new patch 
> compensating for this.

Look forward to it.

> John, now I also know why your version survived this, it did the error 
> correction in the update loop, this kept error small, but it also caused 
> the time to jump around, since it changed the multiplier in the past.

Yep, agreed.

thanks
-john

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