Sun GC maxtenuringthreshold

Question

Hi,

Have a question about Sun GC. The Sun FAQ (old one for 1.4.2) says that the throughput collector does not use the MaxTenuringThreshold (MTT) parameter. Its used only for CMS. http://java.sun.com/docs/hotspot/gc1.4.2/faq.html

I dont know how to verify this, but if its true, how does the throughput collector determine when to promote the young objects to the tenured generation ? Is it done everytime the young generation fills up (in other words MTT = 0 ? ).

Answer 1

If you are talking about a modern (1.6.0) Sun GC, you can download the source code and work out for yourself exactly what is going on. But of course, the behavior could change with different patch levels.

Here are some more recent documents that refer to the -XXmaxTenuringThreshold option:

• Java Tuning White Paper - Sun (2005)
• "The most complete list of -XX options for Java 6 JVM" - Eugene Kuleshov (2006)

and various hints show up in Google searches. But I cannot find any definitive documentation or a definitive answer to your question on the web.