G1 GC是否具有最大区域大小或最大区域数量？

从HotSpot
JVM来源
：

  // Minimum region size; we won't go lower than that.  // We might want to decrease this in the future, to deal with small  // heaps a bit more efficiently.  static const size_t MIN_REGION_SIZE = 1024 * 1024;  // Maximum region size; we don't go higher than that. There's a good  // reason for having an upper bound. We don't want regions to get too  // large, otherwise cleanup's effectiveness would decrease as there  // will be fewer opportunities to find totally empty regions after  // marking.  static const size_t MAX_REGION_SIZE = 32 * 1024 * 1024;  // The automatic region size calculation will try to have around this  // many regions in the heap (based on the min heap size).  static const size_t TARGET_REGION_NUMBER = 2048;

• MIN_REGION_SIZE

  （1MB）和

  MAX_REGION_SIZE

  （32MB）是硬限制；

• TARGET_REGION_NUMBER

  如果在JVM选项中未指定默认区域大小，则该提示仅用于计算默认区域大小。实际数字可能超过此值。