Re: [Xen-users] Time went backwards

[Olivier LAMBERT <lambert.olivier@xxxxxxxxx>]

Please read this :
If a domU crashes or freezes while uttering the famous lasts words
'clocksource/0: Time went backwards', your domU is likely using the
xen clocksource instead of its own clock ticks. In practice, this
seems to be the cause of infrequent lockups under load (and/or
problems with suspending). A workaround is to decouple the clock in
the domU from the dom0:

In your dom0 and domU /etc/sysctl.conf add the line:
xen.independent_wallclock=1. On the dom0, edit the configuration file
of the domU (e.g. /etc/xen/foobar.cfg and add (or expand) the
extra-line: extra="clocksource=jiffies".

These settings can be activated without rebooting the domU. After
editing the configuration files, issue sysctl -p and echo "jiffies">
/sys/devices/system/clocksource/clocksource0/current_clocksource on
the domU prompt.

Because the clock won't be relying on the dom0 clock anymore, you
probably need to use ntp on the domU to synchronize it properly to the
world.



Olivier.
XO Project
http://xen-orchestra.com

On Wed, Feb 17, 2010 at 9:05 AM, Oliver Rojo <orojo@xxxxxxxxxxxx> wrote:
> I am receiving lots of messages like these on my xen virtual machines:
>
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] __ratelimit: 138 messages 
> suppressed
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] clocksource/0: Time went 
> backwards: ret=3b05d54bddc delta=-65371689384312 shadow=3b05d288427 
> offset=2c75df
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] __ratelimit: 133 messages 
> suppressed
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] clocksource/0: Time went 
> backwards: ret=3b188b7d968 delta=-65366666501612 shadow=3b1872eab3b 
> offset=18978b8
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] __ratelimit: 97 messages 
> suppressed
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] clocksource/0: Time went 
> backwards: ret=3b2b910bbd2 delta=-65361560402818 shadow=3b2b134cf7a 
> offset=7dc452f
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] __ratelimit: 198 messages 
> suppressed
> Feb 17 06:57:54 XXX-vm kernel: [61138.593289] clocksource/0: Time went 
> backwards: ret=3b3dabe5629 delta=-65356700410155 shadow=3b39fa01ee9 
> offset=3b1e7453
> Feb 17 06:57:54 XXX-vm kernel: [61138.593290] __ratelimit: 425 messages 
> suppressed
> Feb 17 06:57:54 XXX-vm kernel: [61138.593290] clocksource/0: Time went 
> backwards: ret=3b505b86c49 delta=-65351684410123 shadow=3b505410ae9 
> offset=77a3ab
>
> What do these messages indicate? Did I missed something on my setup?
>
> Oliver
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
>

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