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

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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.?

1
javaspringjvmspring-batchheap-memory

1 Answers

0
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This error is usually thrown when there is insufficient space to allocate an object on the Java heap or if the Java process is spending more than 98% of its time doing garbage collection and if it is recovering less than 2% of the heap and has been doing so far the last 5 garbage collection cycles.

I would first use a Java profiler to determine what methods are allocating large numbers of objects on the heap and make sure that they are no longer referenced after they are not needed. If this doesn't fix the issue and I have confirmed that I need all the objects, the other option would be to increase the max heap size of the program.