You'd get very different results doing atomic operations on counters shared between multiple threads, and with other stuff to do that causes your CPU to serialise and run less out-of-order. That single-threaded benchmark is data, but it doesn’t appear awfully relevant to how naive RC barriers perform versus barriers for coalesced RC or tracing.

Indeed the issue with measuring barriers is that measuring the barrier doesn't suffice; one wants to measure how the barrier affects the rest of execution. This entails coming up with programs that are much less trivial than repeatedly incrementing a counter.