Re: [Xen-devel] Time Skewing on Windows XP

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of Suravee Suthikulpanit
> Sent: 12 March 2013 04:40
> To: George Dunlap; Jan Beulich
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: [Xen-devel] Time Skewing on Windows XP
> 
> Hi,
> 
> While I was investigating the following issue on Windows XP (both 32-bit and
> 64-bit):
> 
> * AMD NPT performance regression after c/s 24770:7f79475d3de7
>     Reference:http://marc.info/?l=xen-devel&m=135075376805215
> 
> 
> On the latest source form xen-unstable, I ran into an issue where the timing
> on the HVM guests skewing about 2x slower than the actual wall clock time.
> This results in the system time slowing down. This is regardless of the
> cpufreq governor scaling. (I tried with both ondemand and performance).
> 
> However, I don't see the same behavior on the Win7 HVM guests. Is this a
> known issue. I assume that XP and Win7 uses different mechanism for
> keeping time (e.g. rdtsc vs. HPET)?
> 

I think XP uses TSC and more recent versions of Windows use PM TIMER. Try 
booting XP with the /USEPMTIMER switch in boot.ini.

  Paul

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