Collecting and Analyzing Java Virtual Machine (JVM) Garbage Collection Data

HPjtune analyzes instrumentation data emitted by the HotSpot JVM Garbage Collector. The data are written to ASCII text files by the JVM when requested with Java command line options. You then open the data collection files in HPjtune for analysis.

Minimum System Requirements for Data Collection

Remember that the above requirements apply to the system where you run the Java application being measured, not where you run HPjtune.

Obtaining Data Collection Files

HPjtune processes three different data collection file types, which you obtain by running your Java application with either of the following options:

Examples

   java -Xverbosegc:file=test01gc.vgc -jar myapp.jar

Runs the java program in the Java archive file myapp.jar and writes GC data to the file test01gc.vgc.

   java -Xloggc:myapp.lgc -XX:+PrintTLE -jar myapp.jar | grep -e " TLAB: " >myapp.tle

Runs the same java program, this time redirecting STDOUT to the pipe for filtering and writing to file myapp.tle. At the same time the GC log is written to file myapp.lgc.

Opening Data Collection Files

You present GC and TLE data capture files to HPjtune either with the File -> Open menu selection or the  toolbar button. HPjtune recognizes the file type based on content, so there is no special open command for GC or TLE data. There is also no dependency on file name extensions to identify a file as containing GC or TLE data.