QEMU/KVM cpu pinning

Question

I have set up my VM with pci passthrough and now I am trying to set up cpupinning. How do I verify that it does in fact work? My config regarding cpu parameters:

...
<vcpu placement="static">4</vcpu>
  <cputune>
    <vcpupin vcpu="0" cpuset="2"/>
    <vcpupin vcpu="1" cpuset="3"/>
    <vcpupin vcpu="2" cpuset="6"/>
    <vcpupin vcpu="3" cpuset="7"/>
  </cputune>
  <cpu mode="host-passthrough" check="none">
    <topology sockets="1" cores="2" threads="2"/>
    <feature policy="disable" name="hypervisor"/>
  </cpu>
...

lscpu -e
CPU NODE SOCKET CORE L1d:L1i:L2:L3 ONLINE    MAXMHZ   MINMHZ
  0    0      0    0 0:0:0:0          yes 4600,0000 800,0000
  1    0      0    1 1:1:1:0          yes 4600,0000 800,0000
  2    0      0    2 2:2:2:0          yes 4600,0000 800,0000
  3    0      0    3 3:3:3:0          yes 4600,0000 800,0000
  4    0      0    0 0:0:0:0          yes 4600,0000 800,0000
  5    0      0    1 1:1:1:0          yes 4600,0000 800,0000
  6    0      0    2 2:2:2:0          yes 4600,0000 800,0000
  7    0      0    3 3:3:3:0          yes 4600,0000 800,0000

I should have assigned the correct hyperthreading pairs. My approach was checking the cpu core frequency while stressing the cpu in the vm, but that takes me nowhere. In fact cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq yields 4.6GHz for all of the cores. Shouldn't 4 of my 8 cores run at around idle frequency?

Answer 1

You can stress each core in the VM one at a time and observe the CPU usage of each core using top or htop on the host. This should confirm which core in the guest corresponds to which core on the guest.