the configuration with only
one server by users who would rather have two sources marked as
falsetickers and know a problem needs to be fixed than unknowingly
follow a bad truechimer.
Is it possible to reword that section?
Thanks,
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overlap. Otherwise they both will be falsetickers.
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. Please be careful to not abuse public servers with too
short interval.
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adjtime() implementations.
Or clamp the adjustment to 500 microseconds so there is no leftover.
Or disable the fast phase correction when started without drift file.
Ditching a very useful feature just because Solaris slews faster than
500 ppm seems a bit excessive to me.
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On Wed, Nov 03, 2010 at 04:06:39PM +, Dave Hart wrote:
On Wed, Nov 3, 2010 at 09:24 UTC, Miroslav Lichvar mlich...@redhat.com
wrote:
On Tue, Nov 02, 2010 at 10:03:30PM +, David L. Mills wrote:
I ran the same test here on four different machines with the
expected results
ppm is the standard rate, Linux is working fine and
the other systems are the bad ones.
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- drift_comp;
clock_offset -= adjustment;
adj_systime(adjustment + drift_comp);
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80a4 84 reachable
Nov 2 14:49:16 localhost ntpd[8526]: 10.34.32.125 96ba 8a sys_peer
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:53 ntpd.new2[3135]: 0.0.0.0 c618 08 no_sys_peer
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the FLL limit to 256 s with
tinker allan 8 or lower.
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]: 192.168.123.2 966a 8a sys_peer
1 Jan 10:13:37 ntpd[3635]: 192.168.123.2 8673 83 unreachable
1 Jan 10:20:08 ntpd[3635]: 192.168.123.3 961a 8a sys_peer
Any explanation for this? I've tried versions 4.2.2, 4.2.4, 4.2.6 and
the latest dev, the result is always the same.
Thanks,
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1.730365 6
51544 8809.102 0.117385634 -135.990 0.017442850 1.626332 6
51544 9400.248 0.0 -135.990 0.00119 1.521295 6
Here is a plot of real frequency offset, not sure if this will be any
help:
http://mlichvar.fedorapeople.org/tmp/ntp_start4_freq.png
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to the daemon loop, but
only with one step.
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here.
Please let me know if you need more information.
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or would rather use an NTP
source as a backup, remove the 127.127.28.0 line and use gpsd just for
the PPS source.
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/clknetsim/).
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what to do with
ntp
now.
Any interesting ntpd messages in syslog?
One additional thing you could try is to disable the kernel discline
by adding disable kernel to ntp.conf. If this helps, it's a kernel
bug or possibly a nano/micro mismatch between kernel and ntpd.
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to be sure
it's replying to all queries.
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cycles
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);
+ tr.l_i -= first.l_i;
LFPTOD(tr, gtod[i]);
}
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to be processed instead.
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phase noise and
0.4ppb/s random-walk frequency noise. In such setting and 16s polling
interval chrony is about 15 times better than ntpd.
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(patched to use smaller MINSTEP):
ntpd[9357]: proto: precision = 0.086 usec
I've seen values as low as 40 ns. The system has to use TSC as
clocksource though.
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better.
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clock and is not the resolution.
With current CPUs the precision is well below 100 ns. (thus the
MINSTEP constant used in ntpd's precision routine is too high)
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/devices/virtual/pps/pps0/assert
(change the sys file as appropriate)
3. let it collect the PPS samples for at least one day
4. hit q and send me the adev.plot file
Thanks,
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http
On Fri, Sep 10, 2010 at 03:11:14PM +0200, Udo van den Heuvel wrote:
On 2010-09-10 15:04, Miroslav Lichvar wrote:
If you have a PPS device and would be willing to run the machine
unsynchronized for a day, I'd like to ask you to measure the Allan
deviation and send it to me.
Interesting
to get similar results as with
real data.
What I'm hoping to get from the survey is a range for random-walk
frequency noise which will give results similar to real oscillators
and which I should focus on in my simulations.
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frequency changes in order of tens of ppm
between reboots. Maybe it's hardware specific.
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is constant or the computer
case is well designed and the temperature of the oscillator is not
affected by other components. In my tests fully loading CPU can change
the frequency by tenths of ppm in less than minute and 1us lock will
be far from PLL's reach even with the minimum poll 3.
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specifies at what update interval will be FLL
used, set it to the polling interval to ensure it's always enabled.
With ntp-4.2.4 it's specified in seconds, with 4.2.6 it's a power of
two.
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On Tue, Aug 03, 2010 at 09:14:34PM +0100, David Woolley wrote:
Miroslav Lichvar wrote:
The most important thing is to set minpoll and maxpoll for the server
specified in ntp.conf. Generally, lower is better unless the network
load to the NTP server is a concern. With ntp-4.2.4 the allowed
SHIFT_PLL 2 can be up to 2 times worse (it seems
this can't be improved by lowering the poll interval) and with very
small jitters it can be about 50 times better.
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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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SHIFT_PLL 4:
http://fedorapeople.org/~mlichvar/clknetsim/test5_ntp.png
You probably know what to expect here, but I was surprised to see that
with high jitter the SHIFT_PLL 4 strata are actually better than their
SHIFT_PLL 2 sources.
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On Wed, Jun 30, 2010 at 09:43:26PM +0100, David Woolley wrote:
Miroslav Lichvar wrote:
and is using the LOCAL driver, the rest have clocks with 1ppb/s
wander. Between all nodes is network delay with exponential
distribution and a constant jitter. The simulations are repeated with
Real
getting time with the
rdtsc instruction instead of making a system call.
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/JPL users when
converting to and from UTC and TAI and eventually to TDB for deep
space missions.
The offset is available in the adjtimex structure, so with some
patching it should work on Linux too.
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with Lisp-style expressions, there are
several random number generators and waveforms available. It's also
possible to use a file with pregenerated or measured values as a
source.
From NTP applications, currently supported are Linux ntpd and chronyd.
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as I can tell.
3. The calling sequence for the ntp_gettime() system call is
incompatible with current use. As a result, access to the TAI-UTC
offset by application programs is not available.
This probably won't be fixed as it would break glibc compatibility.
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() there are several places where it
can return without calling clock_select().
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results.
I can reproduce it with 4.2.6p1 and 4.2.7p32, I haven't tried
anything else.
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/show_bug.cgi?id=1554
It seems to happen when the reachability register wasn't full (or above
a certain limit) when the source stopped providing samples. The source
will stay marked as system peer and ntpd will continue to serve time
even if it's actually not sychronized to anything.
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:
/*
* clear crypto if we change the local address
*/
So it would seem the string is used when the network interface which is
used to send packets to the peer has changed its address and the crypto
stuff had to be reset.
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about it. With only
one source you never know.
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On Thu, Apr 15, 2010 at 03:44:21PM +, unruh wrote:
On 2010-04-15, Miroslav Lichvar mlich...@redhat.com wrote:
Userspace timestamps may decrease the accuracy by more than just 0.5
us. When I compare kernel timestamps and timestamps from gpsd, there
is a 20-40us difference, even when
.
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://fedorapeople.org/~mlichvar/chrony/chrony_vs_ntp.png
With recent chrony, NTP and kernel versions the results might be
different though.
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between chrony and ntpd
though, but I don't really have spare hardware at moment to
really test this out.
As chrony supports only version 3 of the NTP protocol, you might need
to add version 3 to the chrony peer specification in ntp.conf.
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.
On a lightly loaded Gb LAN I'm seeing 2-15us jitter, so I think it's
rather a vendor/model problem than a flaw in Gb ethernet itself.
Disabling interrupt coalescing (ethtool -C on Linux) may help.
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, the calculation doesn't work correctly if the precision is below
resolution. The result is just a random value close to 100 ns. Maybe
get_systime should be called multiple times before calculating the
difference.
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to adjust the PLL time constant. I've
proposed a simple patch that adds a new tinker shifttc command here:
http://bugs.ntp.org/1202
The only other option (beside using a shorter poll interval) seems to
be disabling kernel loop and forcing daemon loop to use FLL by
decreasing Allan intercept.
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On Fri, Jun 26, 2009 at 11:34:11AM +, Ronan Flood wrote:
The question remains why the Brandywine PTS device is claiming synch
to LOCAL(O) with stratum 2.
Maybe the NTP implementation is just replying with the client's refid,
which is INIT first and then LOCAL(0).
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is interpreted in the client as a synchronization
loop. Check tcpdump output.
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Distribution plot:
http://fedorapeople.org/~mlichvar/chrony/chrony_vs_ntp.png
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are 64, 64 and 1024 - as expected.
That's clock filter skipping samples, it may skip up to 7 consecutive
samples based on their dispersion. All samples are recorded in
peerstats.
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