All burstable pods run on cpus specified as reserved in the PerformanceProfile. This is really caused by the *systemd.cpu_affinity=<reserved>* kernel argument which is applied via the PerfProfile.

This is problematic, because reserved can be just 1 - 4 cpus and the node capacity will allow many dozens pods to be crammed there. Not speaking about the infrastructure components...

All pods should really run in the "isolated" space.

4.14 CI builds of OCP as of today and yesterday (2023-06-15+) at least.

Always

1. oc debug node/<worker>
2. Find any burstable container process and run `taskset -pc <pid>`
3. Observe the cpu affinity contains all cpus on the node

4. Add a kernel argument systemd.cpu_affinity=0 (example MachineConfig is attached)
5. oc debug node/<worker>
6. Find any burstable container process again and run `taskset -pc <pid>`
7. Observe the cpu affinity again

Step 7. affinity matches the kernel argument value from step 4.

The step 7. affinity matches the affinity from steps 2-3.

The cgroup of the burstable pod is set up properly and contains all cpus (/sys/fs/cgroups/cpuset/kubepods.slice/.../cpuset.cpus) as expected.