Miroslav,
Exactly as expected. The overshoot exceeds the design limit of 10
percent by as much as 40 percent. That's exactly what the design is
intended to avoid
Dave
Miroslav Lichvar wrote:
On Wed, Jun 30, 2010 at 10:00:06PM +0000, David L. Mills wrote:
The change in SHIFT_PLL would result
in unstable behavior below 5 (32 s), as well as serious transients
if the discipline shifts from the daemon to the kernel and back. All
feedback loops become unstable unless the time constant is at least
several times the frequency update interval, which is this case is
one second. If you do want to explore how stability may be affected,
restore the original design and recompile the distribution with
NTP_MINPOLL changed from 3 to 1.
I recompiled ntpd with NTP_MINPOLL 1 and here is a PLL response plot
for SHIFT_PLL 4 poll 1 and SHIFT_PLL 2 poll 3:
http://fedorapeople.org/~mlichvar/clknetsim/test6.png
The initial offset is 0.1 second, after crossing zero offset, they
both stay in negative.
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