[ntp:questions] ntpd -x option

David Woolley david at ex.djwhome.demon.co.uk.invalid
Sat Mar 14 00:03:33 UTC 2009

Unruh wrote:
> David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:

> This is only if the kenrel does not have the equivalent of the adjtimex
> system call. If it does, ntp uses it to slew the kernel, instead of the
> "once per second" adjustment. That may be the distinction you are drawing
> with the "user space" adjustment. 

We are talking about -x.  As I already pointed out, -x sets clock_max 
1200 times higher than the value at which ntpd abandons the strategy you 
have described and resorts to the old once a second or once every four 
seconds slewed steps.

4.2.4p4 ntp_loopfilter.c:
     334          * Note the system poll is set to minpoll only if the 
clock is
     335          * stepped. Note also the kernel is disabled if step is
     336          * disabled or greater than 0.5 s.
     337          */
     338         clock_frequency = flladj = plladj = 0;
     339         mu = peer->epoch - sys_clocktime;
     340         if (clock_max == 0 || clock_max > 0.5)
     341                 kern_enable = 0;
     342         rval = 1;

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