Treadmill is a "real-time" in-place garbage collection algorithm designed by H. Baker. It is simple, elegant, efficient and surprisingly little known.
but definitely a must-read if you care about that kind of thing
[0] https://lamport.azurewebsites.net/pubs/garbage.pdf
[1] https://plover.com/~mjd/misc/hbaker-archive/RealTimeGC.html