On 21/12/2017 13:50, Vitaly Kuznetsov wrote: > I'm back with (somewhat frustrating) results (E5-2603): v4 (that would be Broadwell)? > 1) Windows on Hyper-V (no nesting): 1350 cycles > > 2) Windows on Hyper-V on Hyper-V: 8600 > > 3) Windows on KVM (no nesting): 1150 cycles > > 4) Windows on Hyper-V on KVM (no enlightened VMCS): 18200 > > 5) Windows on Hyper-V on KVM (enlightened VMCS): 17100 What version were you using for KVM? There are quite a few nested virt optimizations in kvm/queue (which may make enlightened VMCS both more or less efficient). In particular, with latest kvm/queue you could try tracing vmread and vmwrite vmexits, and see if you get any. If you do, that might be an easy few hundred cycles savings. Paolo
