Xen users - Feb 2009 - Paravirtualized DomU clock stops after migrating back

Hi all,

I think this problem is well known, but I cannot say the same for the
solution..

A similar issue was discussed in this mailing list:
http://lists.xensource.com/archives/html/xen-users/2008-08/msg01039.html

There are also two bug reports about it, which are marked as resolved,
somehow...
https://bugzilla.redhat.com/show_bug.cgi?id=426861
http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1282


However, I cannot solve the problem using the workarounds that are discussed
on all those threads.

My problem differs slightly from the ones above:
1. I start the DomU on node1. Its clock works. I migrate the domu from node1
to node2, I open a domu console on node2 and everything is fine. Issuing
"date" always gives the right time. However, when I migrate it back to
node
1, and open console to domu, I observe that the clock stopped working.
"date" gives always the same time, "sleep" won''t
return, etc.. When I
migrate it back to node 2, clock starts working again!

2. This happens after a cold migration too, not necessarily a live one.


I think I did everything recommended on several forums. e.g.:

- On the domu, I set the indepentent wallclock to 1
- I installed ntp client on DomU, I added a couple of ntp servers to
ntp.conf (i.e. 0.pool.ntp.org) and ran ntpd before migration.
- Both nodes are syncronized with the same ntp server.

Nothing helped so far.. am I doing something wrong? Please help if you have
any clue on this.

Cheers
Ercan


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Ok, looks like It''s been solved.

Adding "clock=jiffies" as a kernel parameter in the DomU configuration
did
the trick.

Time still slews more than 30 seconds after every migration though, and
issuing "ntpd -q" with ~10 second intervals corrects the time ~0.01
sec
every time. Not really accurate, but the most important thing is that it
works!

Actually I collect some measurements about resource consumption from those
DomUs, so having an accurate clock is pretty important for those
calculations. The DomUs are not supposed to have an access to the Internet,
so I will have to install my own NTP server. If someone knows a better
workaround for this problem to save me from these boring tasks, I will
appreciate it!

Cheers
Ercan


On Fri, Feb 20, 2009 at 12:29 PM, S. Ercan Yüzbasioglu <
ercan.yuzbasioglu@gmail.com> wrote:
> Hi all,
>
> I think this problem is well known, but I cannot say the same for the
> solution..
>
> A similar issue was discussed in this mailing list:
> http://lists.xensource.com/archives/html/xen-users/2008-08/msg01039.html
>
> There are also two bug reports about it, which are marked as resolved,
> somehow...
> https://bugzilla.redhat.com/show_bug.cgi?id=426861
> http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1282
>
>
> However, I cannot solve the problem using the workarounds that are
> discussed on all those threads.
>
> My problem differs slightly from the ones above:
> 1. I start the DomU on node1. Its clock works. I migrate the domu from
> node1 to node2, I open a domu console on node2 and everything is fine.
> Issuing "date" always gives the right time. However, when I
migrate it back
> to node 1, and open console to domu, I observe that the clock stopped
> working. "date" gives always the same time, "sleep"
won''t return, etc.. When
> I migrate it back to node 2, clock starts working again!
>
> 2. This happens after a cold migration too, not necessarily a live one.
>
>
> I think I did everything recommended on several forums. e.g.:
>
> - On the domu, I set the indepentent wallclock to 1
> - I installed ntp client on DomU, I added a couple of ntp servers to
> ntp.conf (i.e. 0.pool.ntp.org) and ran ntpd before migration.
> - Both nodes are syncronized with the same ntp server.
>
> Nothing helped so far.. am I doing something wrong? Please help if you have
> any clue on this.
>
> Cheers
> Ercan
>
>
>
>

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