[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] Problem correlating TSC read from domU with Xentrace's TSC
> I am trying to correlating performance issue in guest VM with the > scheduling trace from Xentrace. User-mode application in guest VM > periodically dump APIC ID and RDTSC into trace. I also start Xentrace > in Dom0 during the same period. > > However, I notice that range of TSC values report both trace is > completely disjointed. TSC values from Xentrace is always greater than > what guest VM see, even if I start capturing Xen's trace 30s before > capturing trace in guest VM. > > I understand that Xen don't emulate rdtsc() for PV guest and Xentrace > also read rdtsc() during __insert_record(). However, I don't > understand what cause my issue. Any suggestion? I am using Xen > 4.1.1 on Fedora 15 Hi Thawan -- Depending on the underlying hardware, Xen may emulate rdtsc for PV guests. To force this off, set tsc_mode=2 in your guest vm.cfg file (and reboot). For more info on tsc_mode see tscmode.txt in the Xen source tree (or google for it). Dan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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