Re: Time offset / Jitter under FreeBSD
- From: "Bob" <bobsjunkmail@xxxxxxxxxxxxx>
- Date: Mon, 3 Dec 2007 21:40:01 -0500
"Dag-Erling Smørgrav" <des@xxxxxx> wrote in message
news:86fxykdm4z.fsf@xxxxxxxxxxxxx
"Bob" <bobsjunkmail@xxxxxxxxxxxxx> writes:
I installed FreeBSD on a drive, and booted my windows machine from it.
The
FreeBSD port of ntpd shows a offsets in the 20-60 ms range. Issues with
jitter, also. Remember, the same machine running windows is generally sub
millisecond - http://www.pool.ntp.org/scores/74.181.17.243/log offset.
What does 'sysctl kern.timecounter' say?
DES
--
Dag-Erling Smørgrav - des@xxxxxx
What we have here is BSD noob coupled with lack of patience. That, coupled
with the fact that the Windows version seems to have a faster slew rate. I
left it alone long enough, and all is well. The Windows version seems to
figure out the computer clock offset alot faster. The "default" location of
the ntp.drift file is not in /etc. It is of course in /var/db, so all the
looking and fiddling i was doing to the one in /etc was for nothing. I did
build, and am running 4.2.4p4@xxxxxxxx
It's behaving well, except it doesn't like to read my NTP-100 (10.33.90.50),
while the Meinberg windows version (10.33.90.10) does just fine.
BTW, this machine has no disk. It is running on an off the shelf 2 gig USB
memory stick. 512 meg ram, no swap slice. It appears not to access the stick
very often - maybe once every few minutes - but I'm not sure if they are
reads or writes. Anyone here that can tell me if there is a way to see how
often disk writes are occurring? I'd like to see how fast I'm burning up the
flash stick. It's a full minimal install + man pages. The current version of
ntpd was built on this machine.
Thanks for the help.
n2qew# ntpq -p
remote refid st t when poll reach delay offset
jitter
==============================================================================
-ns.unc.edu 129.6.15.28 2 u 6 64 367 46.649 5.865
1.138
+64.236.96.53 .ACTS. 1 u 2 64 317 39.811 2.366
0.269
+68.216.79.113 .ACTS. 1 u 21 64 377 21.753 3.099
0.283
*10.33.90.10 10.33.90.50 2 u 4 16 377 0.211 -0.003
0.025
10.33.90.50 .INIT. 16 u - 64 0 0.000 0.000
0.000
n2qew#
n2qew# ntpq -p 10.33.90.10
remote refid st t when poll reach delay offset
jitter
==============================================================================
-ns.unc.edu 129.6.15.28 2 u 46 64 357 46.198 5.775
0.543
+64.236.96.53 .ACTS. 1 u 22 64 357 38.828 2.178
0.593
+68.216.79.113 .ACTS. 1 u 86 64 376 21.989 3.213
0.719
*10.33.90.50 .GPS. 1 u 7 16 377 0.428 0.057
0.005
n2qew#
ntpdc> kerni
pll offset: -7.889e-06 s
pll frequency: 19.482 ppm
maximum error: 0.021753 s
estimated error: 8e-06 s
status: 2001 pll nano
pll time constant: 4
precision: 1e-09 s
frequency tolerance: 496 ppm
ntpdc>
n2qew# sysctl kern.timecounter
kern.timecounter.stepwarnings: 0
kern.timecounter.nbinuptime: 12748095
kern.timecounter.nnanouptime: 0
kern.timecounter.nmicrouptime: 2041
kern.timecounter.nbintime: 113343
kern.timecounter.nnanotime: 56018
kern.timecounter.nmicrotime: 19303
kern.timecounter.ngetbinuptime: 842
kern.timecounter.ngetnanouptime: 1471
kern.timecounter.ngetmicrouptime: 909935
kern.timecounter.ngetbintime: 0
kern.timecounter.ngetnanotime: 0
kern.timecounter.ngetmicrotime: 6558219
kern.timecounter.nsetclock: 4
kern.timecounter.hardware: ACPI-fast
kern.timecounter.choice: TSC(800) ACPI-fast(1000) i8254(0) dummy(-1000000)
kern.timecounter.tick: 1
n2qew#
.
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