Xen: When Time Flies.. . Too Fast

Today I noticed on a Xen DomU running Debian Squeeze that time seemed to be running a bit too fast, I noticed the same on a Debian Wheezy DomU. They both have in common the kernel 2.6.32-5-xen-amd64.

After breaking a few keyboards I found the following on domU: cat /sys/devices/system/clocksource/clocksource0/available_clocksource xen tsc jiffies cat /sys/devices/system/clocksource/clocksource0/current_clocksource jiffies So I tried changing the clocksource as follows: echo "xen" > /sys/devices/system/clocksource/clocksource0/current_clocksource And voilà, time is back to normal.

To make the changes permanent I changed this in the domU.conf file (on dom0) from: extra="clocksource=jiffies" to extra="clocksource=xen"