Testing workload isolation with a virtual machine

• How virtual machines can use workload isolation

• Red Hat account
• Red Hat OpenShift Container Platform
• Red Hat OpenShift Virtualization
• At least 4 available CPU cores 

Use the OpenShift console or virtctl to create a virtual machine with 4 CPU cores in a project/namespace.

A screenshot of Red Hat console showing a virtual machine created from the virtctl command.

Access the VM and run a stress test

Use virtctl to SSH into the VM and execute the stress-ng command.

# Download and install virtctl if you haven't already
wget --no-check-certificate https://hyperconverged-cluster-cli-download-openshift-cnv.apps.demo-01-rhsys.wzhlab.top/amd64/linux/virtctl.tar.gz
tar zvxf virtctl.tar.gz
mv virtctl ~/.local/bin/

# SSH into the VM and run the test
virtctl -n demo ssh user@vm-name --identity-file=~/.ssh/id_rsa
stress-ng --cpu 4 --cpu-load 100 --temp-path /tmp

Observe Host CPU usage

Checking top on the host node will again show that the QEMU process for the VM is consuming CPU cycles exclusively from the isolated cores (20-23).

# top output snippet
%Cpu19 :  1.7 us,  2.0 sy,  0.0 ni, 96.4 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu20 : 99.0 us,  0.3 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.7 hi,  0.0 si,  0.0 st
%Cpu21 : 96.7 us,  0.3 sy,  0.0 ni,  0.0 id,  0.0 wa,  1.0 hi,  2.0 si,  0.0 st
%Cpu22 : 98.7 us,  0.3 sy,  0.0 ni,  0.0 id,  0.0 wa,  1.0 hi,  0.0 si,  0.0 st
%Cpu23 : 99.0 us,  0.7 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.3 hi,  0.0 si,  0.0 st

Verifying VM Process CPU affinity

Finally, we can confirm the CPU affinity of the VM's QEMU process on the host node. This demonstrates that the entire virtual machine, as a workload, is constrained to the isolated CPU cores.

# Find the PID of the qemu-kvm process for the VM
ps -ef | grep qemu-kvm
# 107        44891   44699 62 03:04 ?        00:04:53 /usr/libexec/qemu-kvm -name guest=demo_centos-stream10-tan-tarantula-34,.............

# Check its CPU affinity
taskset -c -p 44891
# pid 44891's current affinity list: 20-23

Once you have finished this testing, we can take a look at how this all works together behind the scenes.  

• Troubleshoot with Red Hat support