[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] Windows SMP
> > I had to disable both, and PAE. Only APIC=0 would not make any > difference. I > > will some further testing with Citrix Xenserver 5, using the same > virtual > > machine and another copy with their vmpd drivers. I bet that there is no > > difference in performance. It seems to be a Xen architectural issue. Any > > ideas? > > The problem is almost certainly APIC related. APIC=0 actually has no > effect > for a multi-processor HVM guest, since APICs are architecturally > absolutely > required in x86 multi-processor systems. > > The problem is most likely lots of emulated APIC TPR writes slowing things > down. Possible fixes: > 1. Run a Windows guest with the 'lazy TPR' optimisation -- w2k3sp2+, > w2k8, > vista. Or run 64-bit Windows which will write TPR in a different way which > most Intel/AMD CPUs can virtualise efficiently. > 2. Run a new enough Intel processor which has automatic TPR handling even > for 32-bit Windows guests. > 3. Run Citrix drivers which patch Windows to avoid TPR writes. > Can you elaborate on that last point? Does that pass WHQL? I think that 'venefax' is running Windows 2003sp2... does that exclude 'lazy TPR' fix as an option or does it need enabling somehow? Thanks James _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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