Re: [Xen-devel] Massive Instant Clock Jump & Freeze domU Issue (NOT Related to Drift, Live Migration or Saving/Restoring)

[Tom W <tcte.tech@xxxxxxxxx>]

Does your hypervisor tree have this commit in it:

        commit 84628ee52a427b0f0fe50502eb8ffd0eedad0f03
        Author: Jan Beulich <jbeulich@xxxxxxxx>
        Date:   Mon Nov 26 17:20:39 2012 +0100

            x86/time: fix scale_delta() inline assembly

That was responsible for a rash of strange time jumps, although IIRC it
affected the whole system and not individual VMs.

It might be worth looking at the scale_delta function in your kernel,
which I think you will find in arch/i386/kernel/time-xen.c. There was a
fix made to this code in the upstream kernel which may be missing there:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=de2d1a524e94a79078d9fe22c57c0c6009237547

After looking at the latest source for RHEL5, the scale_delta method does not have this change, nor does it have the fix Jan described here: http://markmail.org/message/cngzubj6b6vdo55a

The latest RHEL6 does however have the change you described above.

Would changing independent_wallclock=1 bypass the need for the domU system to call this potentially bad scale_delta method in RHEL5?

Thanks Ian.

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