On 19/03/2018 17:44, Tim Shearer wrote: > In terms of performance, below is a the mpstat output (from the host) for a CPU performing L2 packet forwarding on a pinned guest VCPU. Interrupts on that core are disabled. You can see it switching in and out of userspace constantly. > > $ mpstat -P 5 5 > 11:32:03 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle > Average: 5 6.91 0.00 26.98 0.00 0.00 0.00 0.00 65.78 0.00 0.33 > > # sample trace output: > CPU 1/KVM-11359 [005] d... 2207.865724: kvm_entry: vcpu 1 > CPU 1/KVM-11359 [005] .... 2207.865767: kvm_exit: reason IO_INSTRUCTION rip 0x483213 info c0700001 0 > CPU 1/KVM-11359 [005] .... 2207.865768: kvm_pio: pio_write at 0xc070 size 2 count 1 val 0x0 > CPU 1/KVM-11359 [005] d... 2207.865769: kvm_entry: vcpu 1 > CPU 1/KVM-11359 [005] .... 2207.865771: kvm_exit: reason IO_INSTRUCTION rip 0x483215 info 800040 0 > CPU 1/KVM-11359 [005] .... 2207.865772: kvm_pio: pio_write at 0x80 size 1 count 1 val 0x0 > CPU 1/KVM-11359 [005] .... 2207.865773: kvm_fpu: unload > CPU 1/KVM-11359 [005] .... 2207.865774: kvm_userspace_exit: reason KVM_EXIT_IO (2) Are you running a guest kernel that isn't using CONFIG_KVM_GUEST? Thanks, Paolo
