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[Xen-users] Xen 4 time issue : Clocksource unstable

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Xen 4 time issue : Clocksource unstable
From: Olivier Hanesse <olivier.hanesse@xxxxxxxxx>
Date: Thu, 11 Nov 2010 18:42:45 +0100
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I got some time issue with Xen 4. I am running Debian :

linux-image-2.6.32-bpo.5-xen-amd64     2.6.32-26~bpo50+1   Linux 2.6.32 for 64-bit PCs, Xen dom0 suppor
linux-image-2.6.32-bpo.5-amd64           2.6.32-26~bpo50+1   Linux 2.6.32 for 64-bit PCs
xen-hypervisor-4.0-amd64                    4.0.1-1                    The Xen Hypervisor on AMD64

On a dom0, I got 4 domUs. 3 of them are totally out of sync. 1 is 4s behind

dom0  : Thu Nov 11 18:14:58 CET 2010
domU1: Thu Nov 11 18:14:54 CET 2010
domU2: Thu Nov 11 19:04:34 CET 2010
domU3: Thu Nov 11 19:04:34 CET 2010
domU4: Thu Nov 11 19:04:34 CET 2010

/sys/devices/system/clocksource/clocksource0/current_clocksource is set to "xen" for dom0 and domU.
I am running ntpd only in dom0.

I am pretty sure, that if I reboot the domUs, they will be synced again.
I would like to avoid rebooting them. Rebooting isn't a long term solution ;) Is there another way ?
Some relevant logs :

xm dmesg  :

(XEN) checking TSC synchronization across 8 CPUs: passed.
(XEN) Platform timer is 14.318MHz HPET
(XEN) HPET: 3 timers in total, 0 timers will be used for broadcast
(XEN) ACPI sleep modes: S3
(XEN) Platform timer appears to have unexpectedly wrapped 10 or more times.

dmesg :

[591694.109052] Clocksource tsc unstable (delta = -2999660340870 ns)

And guess what " -2999660340870 ns" is around 50min, which is the difference between domU and dom0.

Any ideas how to solve this issue ?  How guys are you doing to keep your domUs synced with dom0 with xen4 ?


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