Thierry, Thierry MARTIN wrote: > Hello, > > Can anyone tell me if a time shift greater than 2s per day is ""normal"" > on a linux system that has no "external" synchronisation (ntp)? > > I tryied "adjtimex -a" which gives unreliable results: it worked fine on > one machine (less than 1s shift / day) and badly on another one > (several seconds shift / day) > > Any info about this subject would help me.
Which kernel version are you running? Starting with ~2.6.22 a new clock model has made its way into the Linux kernel. There are different modules which can use different hardware timers for timekeeping, and there seem to be some problems with certain modules on certain hardware (i.e. chipsets on the motherboard). To list available clock sources under kernel ~2.6.22 or newer: # cat /sys/devices/system/clocksource/clocksource0/available_clocksource hpet acpi_pm pit jiffies tsc Check which clocksource is currently being used: # cat /sys/devices/system/clocksource/clocksource0/current_clocksource tsc Change the clock source: # echo tsc > \ /sys/devices/system/clocksource/clocksource0/current_clocksource For a test it is also possible to override the default clock source using a boot parameter, e.g.: clocksource=jiffies You may want to try if some other of the available modules does a better job in timekeeping. If the active module doesn't work correctly then the frequency drift often exceeds the maximum drift ntpd can handle. Martin -- Martin Burnicki Meinberg Funkuhren Bad Pyrmont Germany _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
