Do you think it can be done by adjusting GC aggressiveness (or even disabling it for short periods of time) and correlating it with execution time?
In general, for a production JVM like HotSpot, the implicit cost comes largely from the barriers (instructions baked directly into the application code). So even if we disable GC cycles, those barriers are still executing.
If we were to remove barriers during execution, maintaining correctness becomes the bottleneck. We would need a way to ensure we don't mark a live (reachable) object as dead the moment we re-enable the collector.
Thank you for the well written article!
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.