Apr 11, 2012

Java 7 g1 garbage collector documentation

A few days ago Oracle announced the schedule for JDK 8. There are many inofficial articles about new features for Java 8 but in my opinion still some documentation for the new features of Java 7 is missing.
I searched for descriptions of the new garbage collector g1 and found only the following two articles:
  • http://docs.oracle.com/javase/7/docs/technotes/guides/vm/G1.html
    This article is more a whitepaper:
    G1 is the long term replacement of the Concurrent
    Mark-Sweep Collector (CMS). [...] The heap is partitioned into a set of equal-sized heap
    regions, each a contiguous range of virtual memory. G1 compacts as
    it proceeds. It copies objects from one area of the heap to the
    other. Thus, it will not encounter fragmentation issues that CMS
    might encounter.
  • http://www.oracle.com/technetwork/java/javase/tech/g1-intro-jsp-135488.html
    This article contains a description and is the only official source to get the command line options to use this garbage collector:
    G1 is still considered experimental and can be enabled with the following two parameters:

    -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC
    To set a GC pause time goal, use the following parameter:

    -XX:MaxGCPauseMillis =50 (for a pause time target of 50ms)

But it is amazing, that there is no more documentation, graph, etc available for this important new feature....


  1. hey look up this wesite for programmers...www.countcode.com, i worked be myself for 5 months to make it run...you can share and download codes, ask or answer forum questions, and you can count your code lines from your whole life of programming, sincerely Emi

  2. One desired feature in Java is Garbage collector being called immediately after the method call Runtime.getRuntime().gc()
    Right now, JVM does the garbage collection according to its freewill, and does not ensure that GC will be called immediately after the method call.

  3. Danke für den Link ... super Seite!