[PlanetCCRMA] NTP anyone?

Brian Fahrlander kilroy@kamakiriad.com
Fri Jul 25 12:35:02 2003

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On Fri, 2003-07-25 at 13:36, Raymond wrote:
> Florin Andrei wrote:
> >Anyone noticed any anomalies when doing media stuff and running ntpd?
> >
> >Normally, ntpd is not supposed to make the system time jump, but
> >sometimes it does. For example, on some bad systems, if you do things
> >like CD-writing, for some reason the system CPU usage goes through the
> >roof. The system is very unresponsive meanwhile (no matter which
> >kernel), and afterwards you end up with a system clock that's quite a
> >few seconds behind.
> >Shortly thereafter, ntpd makes the clock jump.
> >
> >I also suspect that there are other situation when ntpd makes the system
> >clock do "micro-jumps".
> >

> NTP continuously makes the system time jump when the clock is not correct=
ly in synch with a time server, albeit in very small ncrements. The time in=
crements are slewed to bring the local ntpd in sync with another reference =
time server. In extreme cases of a clock way out of time then ntpd with set=
 the time instead of slewing. AFAIK, this is normal behavior for NTP.
> If you are CD-writing on a bad system it is no surprise that it is unresp=
onsive and that NTP will set the clock shortly thereafter.

    Yeah, NTP is a slightly different thing.  Here's how I do it:

    At boot time I get it close:  "rdate -s time.nist.gov"

    AND THEN I start NTP, so that any changes to the system time are
tiny ones.

    Using it this way, you sync the time at first, and you'll be within
a small fraction of a second, and then NTP acts like a metronome and
makes all it's changes in microseconds or smaller.  This is really the
way it ought to be.  If that's still causing glitches, just kill the ntp
process with "service ntpd stop" to do your video sessions. =20

    If the glitches still seem to stay, it's not NTP. If they stop, then
just "checkconfig --levels 2345 ntpd off" to keep it from restarting.

Brian Fahrl=C3=A4nder          GNU/Linux Zealot, Conservative, and Technoma=
Evansville, IN                    My Voyage: http://www.CounterMoon.com
ICQ  5119262

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