Re: [Xen-devel] Clock jumping during live migrations

[Nathan March <nathan@xxxxxx>]

On 10/27/2011 4:07 AM, Tim Deegan wrote:
> At 15:31 -0700 on 26 Oct (1319643098), Nathan March wrote:
> > Having an issue where the clock on a VM will jump ahead by the timezone
> > offset but only certain directions between certain machines.
> >
> > For example, if I run a "sleep 1; date" loop on the VM and migrate it
> > from xen4 to xen7:
> >
> > Wed Oct 26 21:14:46 PDT 2011
> > Thu Oct 27 04:19:03 PDT 2011
> > xen4 ~ # uname -a
> > Linux xen4 3.0.3 #3 SMP Thu Sep 1 23:39:43 PDT 2011 x86_64 Intel(R)
> I think maybe you need these patches on your dom0 kernel:
>
> http://lists.xensource.com/archives/html/xen-devel/2011-10/msg01762.html
Unfortunately I'm still running into this problem, migrating VM's 
between particular dom0's will result in a jump forward of anywhere from 
minutes to hours. This has persisted through dom0 and xen upgrades (now 
on dom0 3.2.7 / xen 4.1.2) so maybe we're missing something in the domu 
kernel (2.6.32.27)? Reviewing kernel change logs doesn't indicate 
anything's changed in regard to clocksources though.
Examples (just running date on the domU after each migration)

Initially: Mon Jun 18 13:53:48 PDT 2012
Xen2 -> Xen8: Mon Jun 18 13:55:05 PDT 2012 (No shift)
Xen8 -> Xen2: Mon Jun 18 14:27:31 PDT 2012 (+30 approx minutes)
Xen2 -> Xen8: Mon Jun 18 14:28:38 PDT 2012 (No shift)
Xen8 -> Xen2: Mon Jun 18 15:01:21 PDT 2012 (+30 minutes again)

This is now running with a domu kernel of 2.6.32.27 (w/ grsec) and a 
dom0 kernel of 3.2.7 on both dom0's (they should be identical). I've 
tried both the "tsc" and "xen" clocksources in the domU with no effect 
(no others are listed in available_clocksources).
Not sure if this is useful, but while on xen8:
(XEN) dom27: mode=0,ofs=0xffc56b8eee259ecf,khz=2266790,inc=13,vtsc 
count: 37835 kernel, 750 user
After moving to xen2:
(XEN) dom7: mode=0,ofs=0xffc51d4984ee8f42,khz=2266790,inc=14,vtsc count: 
17628 kernel, 71 user
Anyone have any suggestions here?

Thanks,
Nathan

--
Nathan March<nathan@xxxxxx>
Gossamer Threads Inc. http://www.gossamer-threads.com/
Tel: (604) 687-5804 Fax: (604) 687-5806


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