Question

我正在检查不同类型的Java垃圾收集器，我使用以下命令在Debian（挤压）系统上输出G1 GC详细信息：

$ java -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -version 

-XX:MaxHeapSize=130024448 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails   
-XX:+UnlockExperimentalVMOptions -XX:+UseG1GC 
java version "1.6.0_18"
OpenJDK Runtime Environment (IcedTea6 1.8.13) (6b18-1.8.13-0+squeeze2)
OpenJDK Client VM (build 14.0-b16, mixed mode)
Heap
      F 0 space 1024K,   0% used [0xa8700000, 0xa8700000, 0xa8800000)
      F 0 space 1024K,   0% used [0xa8800000, 0xa8800000, 0xa8900000)
      F 0 space 1024K,   0% used [0xa8900000, 0xa8900000, 0xa8a00000)
      F 0 space 1024K,   0% used [0xa8a00000, 0xa8a00000, 0xa8b00000)
      F 0 space 1024K,   0% used [0xa8b00000, 0xa8b00000, 0xa8c00000)
      F 0 space 1024K,   0% used [0xa8c00000, 0xa8c00000, 0xa8d00000)
      F 0 space 1024K,   0% used [0xa8d00000, 0xa8d00000, 0xa8e00000)
   Y    0 space 1024K,  17% used [0xa8e00000, 0xa8e2bc10, 0xa8f00000)

我可以在G1中看到堆布局是大小相等的块（区域），那么字符F和Y的含义是什么，使用的17％用量是多少为吗

我还使用以下命令输出（默认我认为）GC详细信息：

$ java -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -version

-XX:+PrintCommandLineFlags -XX:+PrintGCDetails 
java version "1.6.0_18"
OpenJDK Runtime Environment (IcedTea6 1.8.13) (6b18-1.8.13-0+squeeze2)
OpenJDK Client VM (build 14.0-b16, mixed mode, sharing)
Heap
 def new generation   total 960K, used 180K [0x6f030000, 0x6f130000, 0x71790000)
  eden space 896K,  20% used [0x6f030000, 0x6f05d010, 0x6f110000)
  from space 64K,   0% used [0x6f110000, 0x6f110000, 0x6f120000)
  to   space 64K,   0% used [0x6f120000, 0x6f120000, 0x6f130000)
 tenured generation   total 4096K, used 0K [0x71790000, 0x71b90000, 0x8f030000)
   the space 4096K,   0% used [0x71790000, 0x71790000, 0x71790200, 0x71b90000)
 compacting perm gen  total 12288K, used 24K [0x8f030000, 0x8fc30000, 0x93030000)
   the space 12288K,   0% used [0x8f030000, 0x8f0361b8, 0x8f036200, 0x8fc30000)
    ro space 8192K,  89% used [0x93030000, 0x93763300, 0x93763400, 0x93830000)
    rw space 12288K,  59% used [0x93830000, 0x93f60560, 0x93f60600, 0x94430000)

如何知道此默认值属于哪种类型的GC？ CMS一个或一个并行？

Java GCDetail输出是什么意思？

0 个答案: