What is the meaning of the -XX:NewRatio and -XX:OldSize JVM flags?

java memory garbage-collection options flags
dacanalr picture dacanalr · Jul 28, 2011 · Viewed 37.8k times · Source

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 ?

Answer

Peter Lawrey picture Peter Lawrey · Jul 28, 2011

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

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