Java - JVM Config Basics

Usage of Java Version depending JVM parameters

Java 8 and higher

-server
-Xms<heap size>[g|m|k] -Xmx<heap size>[g|m|k]
-XX:MaxMetaspaceSize=<metaspace size>[g|m|k]
-Xmn<young size>[g|m|k]
-XX:SurvivorRatio=<ratio>
-XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled
-XX:+UseCMSInitiatingOccupancyOnly -XX:CMSInitiatingOccupancyFraction=<percent>
-XX:+ScavengeBeforeFullGC -XX:+CMSScavengeBeforeRemark
-XX:+PrintGCDateStamps -verbose:gc -XX:+PrintGCDetails -Xloggc:"<path to log>"
-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M
-Dsun.net.inetaddr.ttl=<TTL in seconds>
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=<path to dump>`date`.hprof
-Djava.rmi.server.hostname=<external IP>
-Dcom.sun.management.jmxremote.port=<port>
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false

Before Java 8

-server
-Xms<heap size>[g|m|k] -Xmx<heap size>[g|m|k]
-XX:PermSize=<perm gen size>[g|m|k] -XX:MaxPermSize=<perm gen size>[g|m|k]
-Xmn<young size>[g|m|k]
-XX:SurvivorRatio=<ratio>
-XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled
-XX:+UseCMSInitiatingOccupancyOnly -XX:CMSInitiatingOccupancyFraction=<percent>
-XX:+ScavengeBeforeFullGC -XX:+CMSScavengeBeforeRemark
-XX:+PrintGCDateStamps -verbose:gc -XX:+PrintGCDetails -Xloggc:"<path to log>"
-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M
-Dsun.net.inetaddr.ttl=<TTL in seconds>
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=<path to dump>`date`.hprof
-Djava.rmi.server.hostname=<external IP>
-Dcom.sun.management.jmxremote.port=<port>
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false

Best Practices

Explicit Heap

Configure the same value for both Xms and Xmx:

  -Xms<heap size>[g|m|k] -Xmx<heap size>[g|m|k]

Meta space in Java 8 is unlimited by default, where multiple Java processes would concurrence each other. Therefore we should declare the meta space size explicit:

  -Xmn<young size>[g|m|k]

Enable automatic heap dumping on OutOfMemory

Append the following to your $JAVA_OPTS:

  -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/<path>/dump-$(date +"%Y%m%d%H%M%S").hprof

Performance Analysis over GC Logging

Append the following arguments to you $JAVA_OTPS (recommended, may be adjusted):

  -XX:+PrintTenuringDistribution -XX:+PrintGCCause -XX:+PrintGCApplicationStoppedTime -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xloggc:/opt/<path>/gc-$(date +"%Y%m%d%H%M%S").log