add nested virtualization optimizations like 'choom', 'vmtouch', possibly 'renice'

[ssenator]

When running in a nested virtualization environment, external load, esp. I/O, RAM usage or multitennant loads can impact performance severely. Within the hosting node, consider using influencer mechanisms, if available, to set OOM and scheduling policy, including 'choom', 'renice', 'vmtouch' or similar.

Ref: https://github.com/hoytech/vmtouch