Although the tuning parameters give you a good start to JVM tuning, you must monitor GC performance to ensure you have the best settings to meet your needs. There are several tools to help you monitor Oracle JVM performance.
VisualVM
VisualVM provides a centralized console for viewing Oracle JVM performance information and its Visual GC plugin shows garbage collector activities.
Figure 1: VisualVM's Visual GC plugin shows the garbage collector in real-time.
JMX Console
This tool helps display various statistics like Liferay DXP’s distributed cache performance, application server thread performance, JDBC connection pool usage, and more.
To enable JMX connections, add these JVM arguments:
-Dcom.sun.management.jmxremote=true
-Dcom.sun.management.jmxremote.port=5000
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false
If you’re running JMX Console from a another machine, add these JVM arguments too:
-Dcom.sun.management.jmxremote.local.only=false
-Dcom.sun.management.jmxremote.rmi.port=5000
-Djava.rmi.server.hostname=[place IP address here]
Figure 2: VisualVM monitors the JVM using Java Management Extensions.
Garbage Collector Verbose Logging
Add these JVM arguments to activate verbose logging for the JVM garbage collector.
-verbose:gc -Xloggc:/tmp/liferaygc1.log -XX:+PrintGCDetails
-XX:+PrintGCCause -XX:+PrintGCApplicationConcurrentTime
-XX:+PrintGCApplicationStoppedTime
Examining these logs helps you tune the JVM properly.
Note: Adding these JVM arguments generates a heap dump if an
OutOfMemoryError
occurs. The dump is written to the heap dump path specified.
Specify the path to use:
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/heap/dump/path/
Garbage collector log files can grow huge. Arguments like the ones below rotate the log to a new file when the log file reaches a maximum size:
-XX:+PrintGCDateStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10
-XX:GCLogFileSize=50M
These arguments rotate the logs to as many as 10
log files, each with a 50M
size limit.
Now you can monitor garbage collection in the JVM and tune it for top performance.