I wrote a little fork+spinloop program w/100 subprocesses and deployed it with a low (100m) CPU request and no limit. It's certainly driving CPU usage to nearly all 8 of the 8 cores on the machine, but the other processes sharing the node are doing fine.

Prometheus scrapes of the kubelet have slowed down a bit, but are still under 400ms.

Prometheus scrape latency for the node kubelet has increased, but not it's still sub-500ms.

Note that this cluster (which is on EKS) does have system reserved resources.

    [root@ip-10-1-100-143 /]# cat /sys/fs/cgroup/cpu/system.slice/cpu.shares
    1024
    [root@ip-10-1-100-143 /]# cat /sys/fs/cgroup/cpu/kubepods/cpu.shares
    8099
    [root@ip-10-1-100-143 /]# cat /sys/fs/cgroup/cpu/user.slice/cpu.shares
    1024