title: Is G1GC still not officially production ready?
body: <p>I wonder what the official status of the "garbage first" (G1) collector in the JDK 7 release is. I would like to use G1 as a low pause gc alternative to CMS, but only if I can really trust on its robustness.</p>
  
  <p>Before JDK 7 was out, G1 was advertised as the shiny new gc going to replace the CMS collector and even to be the default gc in JDK 7. However, now with Oracle JDK 7u1, G1 is not the default gc on any machine I have tried.</p>
  
  <p>Even though one does not need to specify <code>-XX:+UnlockExperimentalVMOptions</code> anymore when using <code>-XX:+UseG1GC</code> in JDK 7, it's a JVM feature that's officially completely undocumented:</p>
  
  <p><a href="https://stackoverflow.com/questions/8111310/java-7-jdk-7-garbage-collection-and-documentation">Java 7 (JDK 7) garbage collection and documentation on G1</a></p>
  
  <p>The only official document I could find that mentions G1 is seriously outdated and was written long before JDK 7 was out:</p>
  
  <p><a href="http://www.oracle.com/technetwork/java/javase/tech/g1-intro-jsp-135488.html" rel="nofollow noreferrer">http://www.oracle.com/technetwork/java/javase/tech/g1-intro-jsp-135488.html</a></p>
  
  <p>For example, the official "Java HotSpot VM Options" documentation ( <a href="http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html" rel="nofollow noreferrer">http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html</a> ) documents how to enable and tune the other collectors but does not even mention the existence of G1. As if it didn't exist!</p>
  
  <p>This is quite confusing and I wonder what the real status of the G1 and what its future is. Is it really stable yet? Have the remaining issues (like leaks, spurious crashes and missing instrumentation support) been resolved? And if so, why does Oracle treat the G1GC as an undocumented (embarrassing?) secret? Is G1 perhaps a failed project that's now silently discontinued? Or do I need to pay for documentation and support? Or is it just still beta? Can someone enlighten me on what's going on here?</p>