How to make JVM release memory back to OS [duplicate]

Question

I am using GC options XX:+UseParNewGC-XX:+UseConcMarkSweepGC for my application.

As most of you are already experiencing JVM is good at increasing heap up to max heap size, however it does not release memory back to OS. I came across -XX:MaxHeapFreeRatio and -XX:MinHeapFreeRatio but these are ignored for Parallel Garbage Collectors.

Are there special options to force JVM release memory back to OS for -XX:MaxHeapFreeRatio and -XX:MinHeapFreeRatio combination.

Answer 1

On my Java 1.8.0_45 -XX:+UseG1GC makes memory shrink. This is my test:

    MemoryPoolMXBean m = ManagementFactory.getMemoryPoolMXBeans().get(5);
    System.out.println(m.getName());
    byte[] a = new byte[512 * 1024 * 1024];
    System.out.println(m.getUsage().getCommitted() / 1024 / 1024);
    a = null;
    System.gc();
    Thread.sleep(1000);
    System.out.println(m.getUsage().getCommitted() / 1024 / 1024);