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Why does Java Process occupies more memory than Xmx?

2705543Jul 2 2014 — edited Jul 10 2014

Hi,

I'm running a 64-bit application on the 64-bit OS and a 64-bit processor with following startup options:

java -d64 -server -Xms512m -Xmx4096m -Xmn256m -XX:+HeapDumpOnOutOfMemoryError -XX:-DisableExplicitGC -XX:+UseG1GC -XX:+AggressiveOpts -XX:+UnlockExperimentalVMOptions -XX:+DoEscapeAnalysis -XX:MaxGCPauseMillis=400 -XX:GCPauseIntervalMillis=8000 -jar oltpj-processor.jar

But when the application starts it occupies 4.4G to 5.1G memory which is a big concern for me.

Previously, I was running this application on 32-bit system with -Xmx3072m, it was then occupying upto 3.4-3.8G memory.


My Question:

  1. Why occupying more memory then allocated?
  2. Does the JVM occupy all the assigned momory, irrespective of actual physical allocation of the objects?
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Locked on Aug 7 2014
Added on Jul 2 2014
#java, #java-virtual-machine-jvm, #memory
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