WebSphere Liberty verbosegc from Startup Recipe

Consider enabling Java verbose garbage collection on all JVMs, including production. This will help with performance analysis, OutOfMemoryErrors, and other post-mortem troubleshooting. Benchmarks on OpenJ9 show an overhead of less than 1% and usually less than 0.5%.

Add the following to jvm.options (or equivalent) and restart the JVM:

• OpenJ9 JVM (IBM Java or IBM Semeru Runtimes Java):

  -Xverbosegclog:verbosegc.%seq.log,20,50000

• HotSpot JVM (OpenJDK Runtime Environment, Oracle Java, and similar):
  • HotSpot Java >= 9:

    -Xlog:safepoint=info,gc:file=verbosegc.log:time,level,tags:filecount=5,filesize=20M

  • HotSpot Java 8:

    -Xloggc:verbosegc.log
    -XX:+UseGCLogFileRotation
    -XX:NumberOfGCLogFiles=5
    -XX:GCLogFileSize=20M
    -XX:+PrintGCDateStamps
    -XX:+PrintGCDetails

Review verbosegc*log and monitor for high pause times and that the proportion of time in GC pauses is less than ~5-10% using the GCMV tool.

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