MemoryUsage.java

// See http://stackoverflow.com/questions/33318688/will-openjdk-jvm-ever-give-heap-memory-back-to-linux
import java.util.ArrayList;
import java.util.List;

public class MemoryUsage {

    private static void growMemory() throws InterruptedException {
        System.out.println("Allocating/growing memory");
        List<Long> list = new ArrayList<>();
        // Experimentally determined factor. This gives approximately 1750 MB
        // memory in our installation.
        long realGrowN = 166608000; //
        for (int i = 0 ; i < realGrowN ; i++) {
            list.add(23L);
        }

        System.out.println("Memory allocated/grown - sleeping before Garbage collecting");
        Thread.sleep(10*1000);
    }

    public static void main(String[] args) throws InterruptedException {
        System.out.println("Sleeping before allocating memory");
        Thread.sleep(10*1000);

        growMemory();

        System.gc();

        System.out.println("Garbage collected - sleeping forever");
        while (true) {
            Thread.sleep(1*1000);
        }
    }
}