Wednesday, July 18, 2012

SUSE KVM guest 100% cpu usage - lost network - wrong date

There is something wrong with the "kvm-clock" paravirtual clocksource for KVM guests when running the kernel of SLES 11 SP1.

Several times now, I encountered unreachable virtual machines (lost network), 100% cpu usage of these guests as seen from the host, and when logging in to the guest console for further debugging:

  • wrong date, like Sun Feb   5 08:08:16 CET 2597
  • in dmesg: CE: lapis increasing min_delta_ns to 18150080681095805944 nsec

The fix is simple, update to the latest kernel in SLES 11 SP1, like which apparently provides a stable kvm-clock module.

As as side note: I'm using ntpd on the guests.  Some resources report that you should, other tell the opposite.  My experience is that when doing live migrations, clock drifting may appear which is not corrected or too slowly.  Ntpd handles this correctly.

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