Setting Clock Source for VMs on Linux x86-64

Oracle recommends that you set the clock source to tsc for better performance in virtual environments (VM) on Linux x86-64.

1. As the root user, check if the tsc clock source is available on your system.

   # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
   kvm-clock tsc acpi_pm

2. If the tsc clock source is available, then set tsc as the current clock source.

   # echo "tsc">/sys/devices/system/clocksource/clocksource0/current_clocksource

3. Verify that the current clock source is set to tsc.

   # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
   tsc

4. Using any text editor, append the clocksource directive to the GRUB_CMDLINE_LINUX line in the /etc/default/grub file to retain this clock source setting even after a reboot.

   GRUB_CMDLINE_LINUX="rd.lvm.lv=ol/root rd.lvm.lv=ol/swap rhgb quiet numa=off transparent_hugepage=madvise clocksource=tsc"

5. Run the following command to update GRUB and ensure that these settings are retained even after a reboot:

   # grub2-mkconfig -o /boot/grub2/grub.cfg