[ntp:questions] Re: Ntp-4.1.2: tinker step 0;always slew and kernel time discipline
snikolaev at ebs.com
Fri Feb 18 14:52:08 UTC 2005
Thanks for your replies. Actually, I have just got data from my tests
and this is what I am observing.
If "tinker step 0" but the "kernel" is not disabled explicitly, a
(set manually via the date command) is corrected at a rate of about 0.5
millisecond/s as expected,
but overshoots the right time by about the same absolute value of
offset. This happens repeatedly.
For example, from -20 sec it goes all the way to 20 sec offset and then
back to -20 and so on many times.
I did not wait for it to settle down.
When the "kernel" is disabled, it overshooted only by less than 0.5s and
then slowly settled to the correct time.
Actually, it settled to the range of +-120ms around the peer's time.
It looks to me that "disable kernel" offers a saner behavior in this
From: questions-bounces at lists.ntp.isc.org
[mailto:questions-bounces at lists.ntp.isc.org] On Behalf Of David L. Mills
Sent: Thursday, February 17, 2005 9:24 PM
To: questions at lists.ntp.isc.org
Subject: [ntp:questions] Re: Ntp-4.1.2: tinker step 0;always slew and
kernel time discipline
In truth, the kernel is disabled only if the actual correction is
greater than 0.5 s no matter what the tinker. However, there could be
grief if the discipline switches from one to the other. There are a
rather large number of untested and probably dangerous things that might
happen with uncharted combinations of tinkers and I'm not thrilled when
spending lots of time fixing the broken combinations. You are on your
own, but a "diable kernel" command might be appropriate.
Nikolaev, Sergey wrote:
> We have a requirement to always slew the clock even if it means long
> periods of time to correct the offset.
> The NTP documentation mentions this tinker option:
> step step
> The argument is the step threshold, by default 0.128 s. It can be set
to any positive number in seconds. If set to zero, step adjustments will
> Note: The kernel time discipline is disabled if the step threshold is
set to zero or greater than the default.
> However when I set "tinker step 0" and restart ntpd, I see in "ntpdc
> -c sysinfo" that the kernel flag is still enabled. Obviously, it is
> not disabled automaticly just by setting "tinker step 0".
> Do I need to disable it explicitly?
> Thanks in advance,
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