[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Windows SMP
On 29/12/2008 02:59, "Venefax" <venefax@xxxxxxxxx> wrote: > 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. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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