[FIXED] Java: How to optimize the Heap allocation & Garbage collection?

Issue

I have a spring batch application, it consumes ~16GB Memory & 75% of CPU(4core X2.5Ghz) and at times it throws out of memory exception.

I want to optimize the Heap allocation & Garbage collection and tried with the following JVM options so resolve the out of memory exception.

I could not understand some of these parameters as I copy pasted directly from an article

JAVA_OPTS="-server -Xmx20480m -Xms512m -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+CMSClassUnloadingEnabled -XX:+CMSParallelRemarkEnabled -XX:CMSInitiatingOccupancyFraction=30 -XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing -XX:ParallelCMSThreads=2 -XX:+UseCMSCompactAtFullCollection -XX:+DisableExplicitGC -XX:MaxHeapFreeRatio=70 -XX:MinHeapFreeRatio=40 -XX:MaxTenuringThreshold=0 -XX:NewSize=450m -XX:MaxNewSize=650m"

would it really optimize the Heap allocation & Garbage collection and resolve the out of memory exception.?

Solution

First, you need to take a heap dump of the process when it is throwing the OOM error. You can do that by adding -XX:+HeapDumpOnOutOfMemoryError JVM option. After when you have the heap dump try using any of the following tool to analyze your heap dump. Locate which object is growing in the memory and then optimize it. Heap dump analyze tools are :

1. Eclipse Memory Analyzer
2. Heap Hero
3. jxray

Answered By - Prog_G
Answer Checked By - Mildred Charles (JavaFixing Admin)