[ntp:questions] 500ppm - is it too small?

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Tue Aug 18 02:06:42 UTC 2009


Unruh wrote:
> My key worry would be that on Linux, the kernel itself in
>  the adjtimex call imposes a 512PPM limit.  (It has the
>   tickadj option to the adjtimex call which gives far
>   greater latitude-- 100000PPM, but also more complex
>   coding as you have to adjust both the tickadj and the
>   rate in that call.)  Futhermore, the non-kernel route,
>   in which the rate is adjusted via the one second timer
>   interrupt is more difficult.

These seems relevant:

 Linux kernel 2.6.30-rc1
[RFC][PATCH] Adjust SHIFT_PLL to improve NTP convergence.
<http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-05/msg01494.html>

<http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-05/pngnvYEFgcXtV.png>
<http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-05/pngfER6RopGcP.png>

other articles refed:

[PATCH] ntp: convert to the NTP4 reference model
<http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=f19923937321244e7dc334767eb4b67e0e3d5c74>

Re: 2.6.19 -mm merge plans (NTP changes)
<http://lkml.indiana.edu/hypermail/linux/kernel/0609.2/1348.html>
<http://lkml.indiana.edu/hypermail/linux/kernel/0609.3/0433.html>

[ntp:hackers] Time constant too large?
<https://lists.ntp.org/pipermail/hackers/2008-January/003487.html>


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