GCViewer

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GCViewer is a free open source tool to visualize data produced by the Java VM options -verbose:gc and -Xloggc:<file>. It also calculates garbage collection related performance metrics (throughput, accumulated pauses, longest pause, etc.). This can be very useful when tuning the garbage collection of a particular application by changing generation sizes or setting the initial heap size. See here for a useful summary of garbage collection related JVM parameters. For more information on tuning garbage collection on Sun JVMs, take a look at the documentation provided by Sun.

Supported Formats

• Sun JDK 1.4/1.5 with the options -Xloggc:<file> [-XX:+PrintGCDetails]
• Sun JDK 1.2.2/1.3.1/1.4 with the option -verbose:gc
• IBM JDK 1.3.1/1.3.0/1.2.2 with the option -verbose:gc
• IBM iSeries Classic JVM 1.4.2 with option -verbose:gc
• HP-UX JDK 1.2/1.3/1.4.x with the option -Xverbosegc
• BEA JRockit 1.4.2/1.5 with the option -verbose:memory

Best results are achieved with: -Xloggc:<file> -XX:+PrintGCDetails

Data Export

GCViewer can also export the data in CSV (comma separated values) format, which may easily be imported into spreadsheet applications for further processing.

Miscellaneous

GCViewer has been developed with J2SE 1.4 and is licensed under LGPL.

To find out more about how to use GCViewer, please read the article published in Jack Shirazi's performance newsletter.

Other GC related Tools and Links

• VMFlags - Summary of parameters for IBM and Sun JVMs
• visualgc - Part of Sun's jvmstat.
• GCPortal - Article and tool.
• IBM Garbage Collection and Storage Allocation Techniques - Comprehensive document about the IBM garbage collector.
• Tuning Whitepaper - Sun's Java Tuning Whitepaper
• List of Java 6 -XX options - Very short description of each option