Re: calcru: runtime went backwards

On Sun, Feb 12, 2006 at 07:27:37PM +0000, Poul-Henning Kamp wrote:
> In message <20060212220216.F1605_at_free.home.local>, Yuriy Tsibizov writes:
> >On Sun, 12 Feb 2006, Poul-Henning Kamp wrote:
> >> In message <20060212114050.I1160_at_free.home.local>, Yuriy Tsibizov writes:
> >>> while playing 8 PCM streams in parallel (it uses almost all CPU power I
> >>> have).
> >>>
> >>> -CURRENT with last changes to src/sys from imp at 2006-02-11 03:58:07 UTC
> >>
> >> Can you try to update to a more recent current ?  I think you have
> >> not gotten my latest commit to the cpu time accounting at that
> >> point...
> >With -CURRENT up to 2006-02-12 06:57:41 UTC (last commit by scottl)
> >I still can see some calcru messages:
> 
> Right, but these have much smaller deltas than the other ones you saw.
> 
> >calcru: runtime went backwards from 3508844 usec to 3508842 usec for pid 28 (pagezero)
> 
> My theory currently is that these are side effects of the cputick
> calibration code:  If the cputick rate gets measured to be a bit higher,
> the next calculation will result in slightly lower numbers for the
> cpu utilization in microseconds and the warning will fire.
> 
> This will be particularly easy to trigger on machines with power
> management on (laptops mostly).
> 
> My current inclination is to simply not issue this warning if the
> cpu_tick is marked as "variable".

My machine should not be varying CPU-speed either.

Kris