XP Guest Clock Slow

XP Guest Clock Slow

[kvm-user]

Hello,

I just upgraded my hardware to a VT-capable CPU, and am getting up-to-speed
with kvm.

The clock on my XP guest significantly lags (e.g. by 50%) behind the host.
I lose several hours overnight in the guest clock.  (Not just a few seconds)
System load seems to aggravate the problem.

I have seen similar behavior in quick tests on a Vista client.
My Ubuntu client is fine, presumably due to clocksource==kvm-clock in guest.


Everything else works fine in all guest VMs.  (Amazingly well, actually)
Performance is equal to or better what I have been used to with VMware
Server.

Host CPU is Athlon 64 X2 with SB700 chipset.
System dumps (lspci, cpuinfo, etc) available on request (I don't want to
flood)

Host environment is Debian Lenny, with the distribution 2.6.26 kernel.
Currently running a locally compiled/installed kvm-82
I also saw the same issue with the kvm-72 Debian package.

My host clock is set to 'hpet'
| /sys/devices/system/clocksource/clocksource0$ cat *
| hpet acpi_pm jiffies tsc
| hpet

Is there a paravirtual clock driver for M$ clients available?
What is current best practice to work around this problem?

Thanks,

--
Marty

[Resolved] XP Guest Clock Slow

[kvm-user]

Update in case someone else fights the same issue.

Replaced Lenny kernel with 2.6.28 kernel.org compile.
All is well now - At least within a few seconds per day.

--
Marty

-----Original Message-----
From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org] On Behalf
Of kvm-user@goodbit.net
Sent: Friday, January 16, 2009 10:15 AM
To: kvm@vger.kernel.org
Subject: XP Guest Clock Slow

Hello,

I just upgraded my hardware to a VT-capable CPU, and am getting up-to-speed
with kvm.

The clock on my XP guest significantly lags (e.g. by 50%) behind the host.
I lose several hours overnight in the guest clock.  (Not just a few seconds)
System load seems to aggravate the problem.

I have seen similar behavior in quick tests on a Vista client.
My Ubuntu client is fine, presumably due to clocksource==kvm-clock in guest.


Everything else works fine in all guest VMs.  (Amazingly well, actually)
Performance is equal to or better what I have been used to with VMware
Server.

Host CPU is Athlon 64 X2 with SB700 chipset.
System dumps (lspci, cpuinfo, etc) available on request (I don't want to
flood)

Host environment is Debian Lenny, with the distribution 2.6.26 kernel.
Currently running a locally compiled/installed kvm-82
I also saw the same issue with the kvm-72 Debian package.

My host clock is set to 'hpet'
| /sys/devices/system/clocksource/clocksource0$ cat *
| hpet acpi_pm jiffies tsc
| hpet

Is there a paravirtual clock driver for M$ clients available?
What is current best practice to work around this problem?

Thanks,

--
Marty


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Re: XP Guest Clock Slow

[Florent]

kvm-user@goodbit.net a écrit :
> Is there a paravirtual clock driver for M$ clients available?
> What is current best practice to work around this problem?

As in Windows XP and earlier, you can configure the NTP client via the 
control panel.
My host runs a ntp server and all guest are configured to synchronize 
very often.

- Florent

Re: XP Guest Clock Slow

[Ian Kirk]

Florent wrote:

> kvm-user@goodbit.net a ?crit :
> > Is there a paravirtual clock driver for M$ clients available?
> > What is current best practice to work around this problem?
>
> As in Windows XP and earlier, you can configure the NTP client via the control
> panel.
> My host runs a ntp server and all guest are configured to synchronize very
> often.

The implication there, is that KVM does not have a working clock for
Windows guests?

Re: XP Guest Clock Slow

[Florent]

Ian Kirk a écrit :
> The implication there, is that KVM does not have a working clock for
> Windows guests?

I have no problem here, the guests' (XP, 2003, 2008, Vista, 7...) clocks 
are almost as accurate as host's one.

The facts you are describing are close to the behavior of Windows clock 
while it is being synchronized. Depending on the sign of the difference 
between local clock and reference clock, Windows slows down/speeds up 
its clock by 2.

You could have a look at system messages, it can be invoked by a right 
click on "My Computer" -> "Manage". Time service used to output some 
message during the synchro.

- Florent