[jonasn]

That is a creative idea, but unfortunately, Epsilon changes the execution profile too much to act as a clean baseline for barrier costs.

One huge issue is spatial locality. Epsilon never reclaims, whereas other GCs reclaim and reuse memory blocks. This means their L2/L3 cache hit rates will be fundamentally different.

If you compare them, the delta wouldn't just be the barrier overhead; it would be the barrier overhead mixed with completely different CPU cache behaviors, memory layout etc. The GC is a complex feedback loop, so results from Epsilon are rarely directly transferable to a "real" system.