Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 21/12/2017 13:50, Vitaly Kuznetsov wrote: >> I'm back with (somewhat frustrating) results (E5-2603): > > v4 (that would be Broadwell)? > Sorry, v3, actually. Haswell. (the first one supporting vmcs shadowing afaiu). >> 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). This is kvm/queue and I rebased enlightened VMCS patches to it. > > 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. Will do. -- Vitaly
