G1 上的 Java 7 (JDK 7) 垃圾收集和文档 [英] Java 7 (JDK 7) garbage collection and documentation on G1

问题描述

Java 7 已经发布一段时间了，但我找不到任何关于垃圾收集器配置的好资源，特别是新的 G1 收集器.

Java 7 has been out for a while now, but I cannot find any good resources on the configuration of the garbage collectors, specifically the new G1 collector.

我的问题:

1. G1 是 Java 7 中的默认收集器吗?如果不是，我该如何激活 G1?
2. g1 在 Java7 中有哪些可选设置?
3. 是否对 Java 7 中的 cms 或 parallel collector 等其他收集器进行了任何更改?
4. 在哪里可以找到关于 Java 7 垃圾收集的优秀文档?

1. Is G1 the default collector in Java 7 and if not how do I activate G1?
2. What optional settings does g1 have in Java7?
3. Were there any changes made to other collectors like cms or the parallel collector in Java 7?
4. Where can I find good documentation on garbage collection in Java 7?

推荐答案

G1 垃圾收集器不是我安装的 Java 版本 1.7.0_01 中的默认设置.您可以使用一些额外的命令行选项来亲自查看:

The G1 garbage collector is not the default in my installation of Java, version 1.7.0_01. You can see for yourself by using with some extra command line options:

> java -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -version
-XX:InitialHeapSize=132304640 -XX:MaxHeapSize=2116874240 -XX:ParallelGCThreads=4 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseCompressedOops -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC
java version "1.7.0_01"
Java(TM) SE Runtime Environment (build 1.7.0_01-b08)
Java HotSpot(TM) 64-Bit Server VM (build 21.1-b02, mixed mode)
Heap
 PSYoungGen      total 37696K, used 1293K [0x00000007d5eb0000, 0x00000007d88c0000, 0x0000000800000000)
  eden space 32320K, 4% used [0x00000007d5eb0000,0x00000007d5ff3408,0x00000007d7e40000)
  from space 5376K, 0% used [0x00000007d8380000,0x00000007d8380000,0x00000007d88c0000)
  to   space 5376K, 0% used [0x00000007d7e40000,0x00000007d7e40000,0x00000007d8380000)
 PSOldGen        total 86144K, used 0K [0x0000000781c00000, 0x0000000787020000, 0x00000007d5eb0000)
  object space 86144K, 0% used [0x0000000781c00000,0x0000000781c00000,0x0000000787020000)
 PSPermGen       total 21248K, used 2032K [0x000000077ca00000, 0x000000077dec0000, 0x0000000781c00000)
  object space 21248K, 9% used [0x000000077ca00000,0x000000077cbfc288,0x000000077dec0000)

不过，您不再需要启用实验性选项来打开 G1 收集器:

You don't need to enable experimental options to turn on the G1 collector any more, though:

> java -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseG1GC -version
-XX:InitialHeapSize=132304640 -XX:MaxHeapSize=2116874240 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation
java version "1.7.0_01"
Java(TM) SE Runtime Environment (build 1.7.0_01-b08)
Java HotSpot(TM) 64-Bit Server VM (build 21.1-b02, mixed mode)
Heap
 garbage-first heap   total 130048K, used 0K [0x000000077ca00000, 0x0000000784900000, 0x00000007fae00000)
  region size 1024K, 1 young (1024K), 0 survivors (0K)
 compacting perm gen  total 20480K, used 2032K [0x00000007fae00000, 0x00000007fc200000, 0x0000000800000000)
   the space 20480K,   9% used [0x00000007fae00000, 0x00000007faffc288, 0x00000007faffc400, 0x00000007fc200000)
No shared spaces configured.

我不知道你在哪里可以找到任何好的文档.

I don't know where you can find any good documentation.

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