[jboss-user] [Performance Tuning] - Re: Full Garbage Collection every few seconds – GC frees very little memory (JBoss 4.2.3 with JDK 1.5.0 64-bit)

Peter Johnson do-not-reply at jboss.com
Fri Nov 19 11:14:13 EST 2010


Peter Johnson [http://community.jboss.org/people/peterj] created the discussion

"Re: Full Garbage Collection every few seconds – GC frees very little memory (JBoss 4.2.3 with JDK 1.5.0 64-bit)"

To view the discussion, visit: http://community.jboss.org/message/572010#572010

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Don't set NewRatio to 1. This means that the young gen and old gen are the same sizes. The JVM will do a full collection if the old gen does not have enough to hold all of the object in the young gen (note I wrote 'all', and not 'alive', the determination of whether to do a full vs minor collection takesp lace before the JVM figures out how many objects will survive a minor collection).  I recommend setting it to 3 or 4.

>From the data you posted, the "bad" run seems to be tenuring objects immediately.

If you suspect a memory leak, take a heap dump and anlayze it with VisualVM.

You might want to gather and plot the GC stastics. See these white papers:
Java Garbage Collection Statistical Analysis 101
Java Garbage Collection Performance Analysis 201
at  http://www.cmg.org/cgi-bin/search.cgi?q=java+peter+johnson&x=30&y=10 http://www.cmg.org/cgi-bin/search.cgi?q=java+peter+johnson&x=30&y=10

Also, dig through this forum, it contains many tuning suggestions (including more details about using VisualVM and spotting memory leaks)
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