[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Time Skewing on Windows XP
On 03/12/2013 11:55 AM, Suravee Suthikulanit wrote: On 3/12/2013 4:13 AM, Paul Durrant wrote:I think XP uses TSC and more recent versions of Windows use PM TIMER. Try booting XP with the /USEPMTIMER switch in boot.ini.-----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 and64-bit): * AMD NPT performance regression after c/s 24770:7f79475d3de7 Reference:http://marc.info/?l=xen-devel&m=135075376805215On 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 aknown issue. I assume that XP and Win7 uses different mechanism for keeping time (e.g. rdtsc vs. HPET)?PaulPaul,That still doesn't help in this case. I still see the WindowsXP guest time skewing. Also, I would not think the normal RDTSC skewing should be this severe (0.5x comparing to the wall-clock time). I believe TSC is usually emulated. Try adding "tsc_mode=2" to your configuration so that RDTSC(P) is never intercepted. -boris _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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