I am starting my java app with the following command line :
java -XX:+PrintCommandLineFlags -verbose:gc -XX:+PrintGCDetails \ -XX:+UseConcMarkSweepGC -jar start.jar
The JVM enables the following options:
-XX:MaxNewSize=87244800 -XX:MaxTenuringThreshold=4 -XX:NewRatio=7 -XX:NewSize=21811200 -XX:OldPLABSize=16 -XX:OldSize=65433600 -XX:+PrintCommandLineFlags -XX:+PrintGC -XX:+PrintGCDetails -XX:+UseCompressedOops -XX:+UseConcMarkSweepGC -XX:+UseParNewGC
Can anyone explains me the meaning of NewRatio and OldSize ? In particular OldSize is the initial size of the tenured generation ?
JVM arguments are flags that are passed to the Java Virtual Machine at the time the application is launched. On Linux or Mac machines, they can be provided through the JAVA_OPTS setting in the whd.conf file.
There are three types of options that you can add to your JVM, standard, non-standard and advanced options. If you apply an advanced option, you always precede the option with -XX: . Similarly if you're using a non-standard option, you'll use -X . Standard options don't prepend anything to the option.
What is Java Virtual Machine (JVM)? Java Virtual Machine, or JVM, loads, verifies and executes Java bytecode. It is known as the interpreter or the core of Java programming language because it executes Java programming.
The NewRatio is the ratio of old generation to young generation (e.g. value 2 means max size of old will be twice the max size of young, i.e. young can get up to 1/3 of the heap).
The OldSize is not one of the documented options, but I assume it's the size of the tenured space http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html
Since NewRatio is already well explained, the following should help with OldSize.
Here, OldSize => default size of the tenured generation. This is the default size of tenured till the time ergonomics comes into play.
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