Java Garbage Collection Monitoring

Question

I have a project in Netbeans that I am profiling (using Java 7). What I am looking for is, upon a garbage collection, how much memory from the Eden space is going into the Survivor spaces, and if there is any memory overflowing into the Tenured space. On top of that, I am looking for how the Tenured space is growing in size over time.

I print GC stats but I only get info like this:

2339.967: [GC 2339.967: [ParNew: 66213K->4522K(69376K), 0.0161101 secs] 284589K->223320K(369484K), 0.0161685 secs] [Times: user=0.03 sys=0.00, real=0.02 secs] 
2344.543: [GC 2344.543: [ParNew: 66218K->4520K(69376K), 0.0161084 secs] 285016K->223739K(369484K), 0.0161647 secs] [Times: user=0.03 sys=0.00, real=0.02 secs] 
2349.118: [GC 2349.118: [ParNew: 66216K->4519K(69376K), 0.0159046 secs] 285435K->224159K(369484K), 0.0159587 secs] [Times: user=0.03 sys=0.00, real=0.02 secs] 

Anyone know of a way to figure out the information I am looking for?

Thanks!

Answer 1

Here are some useful GC flags:

-XX:+PrintGCDetails 
-XX:+PrintGCTimeStamps
-XX:+PrintClassHistogram
-XX:+PrintTenuringDistribution
-XX:+PrintGCApplicationStoppedTime

-XX:+PrintTenuringDistribution should give you what you are looking for.

Answer 2

Oracle's JDK comes standard now with jvisualvm which is a free profiler. It will show you what's eating up memory, cpu, threads, network time, db access, etc. Yes, it even shows GC time and a bunch of other goodies about GC in general.

Best part, it's free! (and it may already be installed on your system if you have Oracle JDK)

http://www.youtube.com/watch?v=dUQqmnmCBbg

http://docs.oracle.com/javase/6/docs/technotes/tools/share/jvisualvm.html