> Hello,
>
> I donīt know what the initial reasoning for "500/HZ" was, but I think
> the value for tickadj is way too small in the Linux kernels.
>
> (tickadj limits the speed of a adjtime() system call)
>
> The current rate is 0.5ms per second. Thus a correction of 128ms
> needs 256s, almost 5 minutes. A correction of one second (not unusual
> if the computer was powered down for a day) almost needs half an hour.
IMHO 128ms is a pretty huge difference and should almost never happen.
and if it happens, waiting 1/2 hour shouldn't be a problem (as it
never happens anywy -- per definition;)
and at powerup you first should use ntpdate or similar to step the clock then.
> The current rate of 0.05% (500PPM) is too slow in most cases. Many
> systems use much larger values.
>
> I'm suggesting to boost the value of tickadj by a factor of 100.
> Therefore tickadj will be 50000/HZ, 500 for i386. This will result in
> a correction of 50ms per second (5%).
NO, that's _WAY_ too large! if you're trying to do some timing/benchmark
in this period you'd get 5% error just because of tickadj.
IMHO that's completely out of range! waiting a bit longer to get clocks
in sync is much preferable than to risk 5% errors in timing/sleep intervals
etc.
> (My PPSkits added the ability to adjust the value of tickadj during
> runtime, but we need a reasonable default for most cases. BTW:
> thereīs an additional patch to fix compilation problems on i386 with
> PPSkit-0.6.0: PPSkit-0.6.0-add-1.diff.gz, available at the usual
> sites since this morning)
>
> I'm not subscribed to this list, but I'm willing to accept any
> contributions regarding this thread. If nobody objects, I'll put a
> higher value in the next PPSkit, and finally I'll suggest a patch for
> the stable kernel.
>
> Regards,
> Ulrich
> P.S.: I'm suggesting to merge PPSkit-0.6 into the upcoming Linux 2.3
> tree. Currently FreeBSD is way ahead in timekeeping (according to Mr
> Mills and Mr. Kamp)...
>
>
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Harald
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