17.19. Configuring Clock Sources

To list the available clock sources on your system, issue the following commands:
~]$ cd /sys/devices/system/clocksource/clocksource0/
clocksource0]$ cat available_clocksource
kvm-clock tsc hpet acpi_pm 
clocksource0]$ cat current_clocksource
kvm-clock
In the above example, the kernel is using kvm-clock. This was selected at boot time as this is a virtual machine. Note that the available clock source is architecture dependent.
To override the default clock source, append the clocksource directive to the end of the kernel's GRUB menu entry. Use the grubby tool to make the change. For example, to force the default kernel on a system to use the tsc clock source, enter a command as follows:
~]# grubby --args=clocksource=tsc --update-kernel=DEFAULT
The --update-kernel parameter also accepts the keyword ALL, or a comma separated list of kernel index numbers.
See Chapter 25, Working with GRUB 2 for more information on making changes to the GRUB menu.