[ntp:questions] NTP vs chrony comparison (Was: oscillations in ntp clock synchronization)

Petri Kaukasoina kaukasoina708n8s6l3g0 at sci.fi
Sat Jan 26 10:59:06 UTC 2008


Hal Murray <hal-usenet at ip-64-139-1-69.sjc.megapath.net> wrote:
>
>That's a bug in the TSC calibration code.
>
>Recent Linux kernels use the TSC for timekeeping.  (At least on the
>systems I work with.)  There may be a simple command line option
>to use another chunk of hardware.

Yes. cat /sys/devices/system/clocksource/clocksource0/available_clocksource
prints the available clocksources, for example: "tsc acpi_pm jiffies". 
cat /sys/devices/system/clocksource/clocksource0/current_clocksource shows
which source is used, and
echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
makes it to use acpi_pm. Of course, ntpd must recalibrate the frequency drift
then. After that the drift value seems to be correct after reboots! The time
source can be selected at boot time by adding "clocksource=acpi_pm" to the
kernel command line.




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