[TriLUG] Xen HVM guest has severe clock drift

[Igor Partola]

It's with ThrustVPS. They are a budget provider, so I guess you get
what you pay for. They do offer a PV option, and otherwise their
performance seems fine so I am wondering if switching to that would
work.

Igor

On Thu, Mar 10, 2011 at 10:43 AM, Joseph S. Tate
<dragonstrider at gmail.com> wrote:
> Ugh, who's it with so we know to stay far away?  Xen does not have an
> independent time source, it's clock is controlled by the hypervisor.
> NTP can't keep up because a xen guest cannot set the clock.
>
> The only decent VPS I've had is with slicehost/rackspace.  All the
> other ones have sucked in one way or another, even Linode.
>
> On Thu, Mar 10, 2011 at 9:02 AM, Warren Myers <volcimaster at gmail.com> wrote:
>> Sounds like the host is severely overloaded. I personally haven't seen this
>> kind of clock drift since the early days of VMware Server trying to run too
>> many guests at once on a laptop, or a light physical machine trying to run
>> ESX with some heavy-lift VMs
>>
>> -WMM
>>
>> On Thu, Mar 10, 2011 at 07:06, Igor Partola <igor at igorpartola.com> wrote:
>>
>>> Good morning.
>>>
>>> I recently rented a VPS from a provider that runs on a Xen HVM
>>> platform. I am running Ubuntu 10.10 i686 (2.6.35-22-generic-pae) on
>>> it. I continuously run ntpd, but the clock drifts by as much as 30
>>> seconds in 5 minutes and NTP cannot keep up. Has anyone experienced
>>> this? What could be the root cause of this problem?
>>>
>>> Here are some details:
>>>
>>> $ dmesg | grep clock
>>> [    0.160000] Measured 347 cycles TSC warp between CPUs, turning off TSC
>>> clock.
>>> [    0.396000] * this clock source is slow. Consider trying other clock
>>> sources
>>> [    0.550448] Switching to clocksource acpi_pm
>>> [    0.653135] rtc_cmos 00:05: setting system clock to 2011-03-09
>>> 02:45:40 UTC (1299638740)
>>>
>>> $ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
>>> acpi_pm
>>>
>>> $ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
>>> acpi_pm
>>>
>>> So far I've tried the following things:
>>>
>>> 1. I tried disabling ACPI.
>>> 2. I replaced openntpd with ntp and added "tinker panic 0" to the top
>>> of my /etc/ntp.conf file
>>> 3. I read up about xen.independent_wallclock flag, which from what I
>>> can tell applies only to Xen PV.
>>> 4. Contacted the hosting provider who had little useful advice, aside
>>> from "you should install an ntp deamon."
>>>
>>> What could be the root cause of this problem? Is there any sort of
>>> remedy aside from just running an ntp daemon and losing lots of clock
>>> time?
>>> --
>>> This message was sent to: Warren <volcimaster at gmail.com>
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>>
>>
>>
>> --
>> Warren Myers
>> http://warrenmyers.com
>> http://twitter.com/volcimaster
>> http://www.linkedin.com/in/warrenmyers
>> --
>> This message was sent to: Joseph Tate <dragonstrider at gmail.com>
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>>
>
>
>
> --
> Joseph Tate
> Personal e-mail: jtate AT dragonstrider DOT com
> Web: http://www.dragonstrider.com
> --
> This message was sent to: Igor Partola <igor at igorpartola.com>
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>