Would be fun to try to compare this with a decent GC and see what the difference is likely to be. The reason why I say this is because Javas default GC pre-allocates a heap (a Java allocation is mostly just bumping a pointer), and since it "frees" memory by copying survivors to a new space you also avoid fragmentation.

If it turns out that what you mostly pay for, when using a GC, is that collection happens at one point in time instead of incrementally, then Go's plan for the evolution of their GC just became a lot more interesting.