VisualVM shows double Xmx as Max Heap Size

Question

I have the following problem:

There is a Java VM with Xmx Option set to 70000m = 70GB (Yes, it is that big). But if I monitor the before mentioned JVM, Max Heap is shown as 140000m (as seen in the screenshot).

Following a listing of used JVM options:

-XX:+UseG1GC
-Duser.timezone=Europe/Berlin
-Djava.security.egd=file:///dev/urandom
-Dsun.rmi.transport.tcp.handshakeTimeout=180000
-Dsun.rmi.dgc.client.gcInterval=600000
-Dsun.rmi.dgc.server.gcInterval=600000
-verbose:gc
-XX:CICompilerCount=2
-Xrunjdwp:transport=dt_socket,server=y,address=3997,suspend=n
-Xms70000m
-Xmx70000m
-XX:+UnlockExperimentalVMOptions
-XX:G1HeapRegionSize=32
-XX:MaxGCPauseMillis=200
-XX:G1NewSizePercent=2
-XX:G1MaxNewSizePercent=60
-XX:ParallelGCThreads=8
-XX:ConcGCThreads=2
-XX:InitiatingHeapOccupancyPercent=45
-XX:G1MixedGCLiveThresholdPercent=65
-XX:G1HeapWastePercent=10
-XX:G1OldCSetRegionThresholdPercent=10
-XX:G1ReservePercent=10

Has anybody a hint, why VisualVM shows double max heap size?

Answer 1

This is a bug in visualVM when using the G1 garbage collector, the max is not actually this large. Jconsole does report it correctly.

The following report provides a possible explanation. The reason here is that the different generations no longer have a fixed size, but instead the max size for each is the size of the full heap (as they can both use as much as needed). I have not been able to find any official bug report for this yet.