Re: [chrony-users] makestep in Chrony

[Hei Chan <structurechart@xxxxxxxxx>]

Thanks Miroslav and Bill!

One last related question -- how can I be able to tell the sync/calibration is done after I manually ask chrony to synch/calibrate?

I saw one of the posts 4 years ago suggesting that there is no way?

Which command is better to force chrony to synchronize time right now -- chronyc burst or chronyc waitsync?

Which command is better to force chrony to synchronize time right now --...

Or even better -- is there a way that I can call through a C API and get a callback or get blocked after it is done?

Thanks!

On Wednesday, May 9, 2018, 2:58:44 PM GMT+8, Bill Unruh <unruh@xxxxxxxxxxxxxx> wrote:

William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/

On Wed, 9 May 2018, Miroslav Lichvar wrote:

> On Sun, May 06, 2018 at 10:30:48AM +0000, Hei Chan wrote:
>> Hi,
>> I am reading this:https://chrony.tuxfamily.org/manual.html#makestep-command
>> It mentions, "Normally chronyd will cause the system to gradually correct any time offset, by slowing down or speeding up the clock as required".  Most of the Linux machines are using TSC as the source:$ cat /sys/devices/system/clocksource/clocksource0/current_clocksourcetsc
>> Given a machine using TSC as the clock source and new Intel CPUs have invariant TSC, how can chrony slow down or speed up the clock?  I am sure I misunderstand the doc.
>
> The clocksources don't change their frequency. It's the software
> system clock maintained by the kernel, whose frequency is adjusted by
> the adjtimex(2) system call.

To expand, there is counter that counts the pulses in TSC, but those pulses
need to be converted into seconds. That conversion factor can get changed by

the adjtimex.