G1, CMS, Shenandoah, or Zing? Heap size at 8GB or 31GB? compressed pointers? Region size? What is the maximum break time? Throughput or Latency... What gain? MaxGCPauseMillis, G1HeapRegionSize, MaxTenuringThreshold, UnlockExperimentalVMOptions, ParallelGCThreads, InitiatingHeapOccupancyPercent, G1RSetUpdatingPauseTimePercent, which parameters have the most impact?