Are you hallucinating or am I? This implementation is 200 lines of Python. Did you mean to link to a C version?

I found reading Linux source more useful than learning about xv6 because I run Linux and reading through source felt immediately useful. I.e, tracing exactly how a real process I work with everyday gets created.

Can you explain this O(n2) vs O(n) significance better?

agreed - no one else is saying this.