What does the ":=" indicate in the JVM arguments list, in OpenJDK?

Question

I wanted to see all the JVM arguments available in openjdk 1.8, and executed the following command:

java -XX:+PrintFlagsFinal -version

It outputted all the available arguments in JVM, and I observed that a few flags are having the following format:

uintx MaxHeapSize   := 9449766912  {product} 

bool UseParallelGC  := true        {product}

In the above flags, what does the ":=" indicate?

score 1 · Accepted Answer · answered Oct 03 '16 at 07:47

1

:= denotes that the flag value was overriden either by JVM ergonomics or manually via a command line option.

Here is the source of the function that prints flags.

answered Oct 03 '16 at 07:47

apangin

Thanks. That was helpful. Another think is there any java doc/article available explaining all the JVM arguments and categorized by GC algorithm type. – Purushothama Yanamala Oct 03 '16 at 07:57
1

@PurushothamYanamala See [this question](http://stackoverflow.com/questions/7833209/jvm-options-list-still-being-maintained-post-oracle). The most complete list is in the [source code](http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/file/58d961f47dd4/src/share/vm/runtime/globals.hpp#l499). – apangin Oct 03 '16 at 08:05
Plus a [separate file](http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/file/58d961f47dd4/src/share/vm/gc_implementation/g1/g1_globals.hpp#l33) with G1-specific options. – apangin Oct 03 '16 at 08:07

score 0 · Answer 2 · answered Oct 03 '16 at 07:45

0

The := indicates it is the current value.

If you haven't changed it then this is the default value.

I often use this option with grep to find what I want.

answered Oct 03 '16 at 07:45

Peter Lawrey

2 Answers2