"Granted, I have no idea how much overhead is imposed by atomic operations vs. a stop-the-world or concurrent GC." An atomic read/write/increment/decrement is

"Granted, I have no idea how much overhead is imposed by atomic operations vs. a stop-the-world or concurrent GC." An atomic read/write/increment/decrement is a non-blocking (from the point of the view of a user code running on the CPU) CPU operation. The CAS operations required to do atomic inc/dec are relatively expensive compared to normal memory read/writes of course but nowhere near the scale of stop-the-world GC (where all threads in the runtime have to be blocked for a potentially large amount of time, sometimes measured in whole seconds or even 10's of seconds for large heaps). Anyone who has had to troubleshoot JVM's handling large heaps (in the ~10GB range) quickly learns to love deterministic costs of refcounted resource management.