Re: kvm linux guest hanging for minutes at a time

[Thomas Fjellstrom <thomas@fjellstrom.ca>]

On August 9, 2011, Avi Kivity wrote:
> On 08/07/2011 05:06 PM, Thomas Fjellstrom wrote:
> > Occasionally when there's heavy cpu and/or io load, a kvm guest will lock
> > up for minutes at a time, last occurrence was for about 12 minutes or
> > so, and the guest itself reported:
> > 
> > [1992982.639514] Clocksource tsc unstable (delta = -747307707123 ns)
> > 
> > in dmesg after it came back. The only other hint as to what is going on
> > is that the irq count for "local timer requests", virtio-input and
> > virtio- requests spikes rather high. Also one of the cpu cores on the
> > host was pegged the entire time.
> > 
> > The last thing to cause a hang was an "aptitude upgrade" in the guest,
> > which was a bit behind, so it had to update over 300 packages.
> > 
> > The host is running 2.6.38-1-amd64 (2.6.38+32) from debian, qemu-kvm
> > 0.14.0, and the guest was running 2.6.38-2-amd64 (not sure on the +
> > number).
> > 
> > Is this a known problem, thats hopefully fixed in newer kernels and
> > qemu/kvm packages?
> 
> Your guest isn't using kvmclock for some reason.  Is it compiled in the
> guest kernel?  What are the contents of
> /sys/devices/system/clocksource/clocksource0/available_clocksource and
> /sys/devices/system/clocksource/clocksource0/current_clocksource (in the
> guest filesystem)?

Hi, it seems it is using kvm-clock:

$ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
kvm-clock hpet acpi_pm
$ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
kvm-clock

-- 
Thomas Fjellstrom
thomas@fjellstrom.ca