G1 GC是否具有最大区域大小或最大区域数量？

Question

在研究G1
GC时，我发现了这篇文章：http
:
//www.oracle.com/technetwork/articles/java/g1gc-1984535.html。在该文章中，内容如下：

G1
GC是一个区域化的，按代划分的垃圾收集器，这意味着Java对象堆（堆）被划分为多个大小相等的区域。启动时，Java虚拟机（JVM）设置区域大小。区域大小可以从1
MB到32 MB不等，具体取决于堆大小。目标是不超过2048个区域。

这是否意味着G1 GC可以处理的Java堆内存的最大大小为2048 * 32M，如果超过该大小，将会发生什么？

Answer 1

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。