| Re: [chrony-users] makestep in Chrony |
[ Thread Index |
Date Index
| More chrony.tuxfamily.org/chrony-users Archives
]
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.