On Sun, Jan 05, 2003 at 11:05:03PM +0100, Rob van der Heij wrote: > At 05:28 05-01-03, Matt Zimmerman wrote: > > >Though, still, waking up once per second should be much less of an impact > >than the 100Hz timer interrupt. > > Still, once per second is a lot more than we want. Especially since we > don't really care what the clock is when the server would otherwise be > idle. > > I found at http://www.eecis.udel.edu/~ntp/ntp_spool/html/ntpd.html a > description of how the Poll Interval is reduced based on observed jitter > and wander of the clock. It talks about 10's of seconds at least.
The poll interval has to do with polling network time servers using the NTP protocol. This is usually on the order of minutes rather than seconds. The 1-second interval is to wake up and tend to the local system clock. Regarding the earlier suggestion of running ntpdate from cron, the NTP documentation has this to say: "In some cases it may not be practical for ntpd to run continuously. A common workaround has been to run the ntpdate program from a cron job at designated times. However, this program does not have the crafted signal processing, error checking and mitigation algorithms of ntpd. The -q option is intended for this purpose. Setting this option will cause ntpd to exit just after setting the clock for the first time. The procedure for initially setting the clock is the same as in continuous mode; most applications will probably want to specify the iburst keyword with the server configuration command. With this keyword a volley of messages are exchanged to groom the data and the clock is set in about 10 s. If nothing is heard after a couple of minutes, the daemon times out and exits. After a suitable period of mourning, the ntpdate program may be retired." -- - mdz
