Encourage the JVM to GC rather than grow the heap?

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You could try specifying -XX:MinHeapFreeRatio and -XX:MaxHeapFreeRatio to control heap expansion and shrinking:

  • -XX:MinHeapFreeRatio – when the percentage of free space in a generation falls below this value the generation will be expanded to meet this percentage. Default is 40.
  • -XX:MaxHeapFreeRatio – when the percentage of free space in a generation exceeded this value the generation will shrink to meet this value. Default is 70.

You might also want to experiment with concurrent GC by specifying -XX:+UseConcMarkSweepGC. Depending on your application it could keep the heap size lower at the cost of additional CPU cycles.

The JVM is otherwise going to use the memory you specify as available when it’s optimal do to so. You could specify a lower amount like -Xmx768m to keep it contained and it might run fine, although you would increase your risk of running out of memory in a heavy load scenario. Really the only way to use less memory overall is to write code that uses less memory 🙂

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