ADDITIONAL SYSTEM INFORMATION :
Linux 64 bit, Windows 10 64 bit

A DESCRIPTION OF THE PROBLEM :
Value returned by java.lang.management.MemoryUsage.getUsed() for eden space usage does not match with the value shown by jcmd <pid> GC.heap_info command. Following code always shows eden space usage as 0.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Following code prints the memory usage on console. Once the program prints memory usage, put it in background and capture the jcmd output using "jcmd <pid> GC.heap_info" command. Compare the eden space usage values between these two approaches.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Eden space usage as reported by java.lang.management.MemoryUsage should be close to the value reported by jcmd output.
ACTUAL -
Eden space usage reported by java.lang.management.MemoryUsage is always 0.

---------- BEGIN SOURCE ----------
import java.lang.management.ManagementFactory;
import java.lang.management.MemoryPoolMXBean;
import java.lang.management.MemoryUsage;
import java.util.HashSet;

public class HeapUsageTest {

	public HeapUsageTest()
	{
        System.out.println("Before ");
        printHeapUsage();
        HashSet<String> set = new HashSet<>();
        for (int i = 0; i<10000000; i++) {
            set.add(String.valueOf(i));
        }
        System.out.println("After");
        printHeapUsage();
		
	}
    public static void main(String[] args) throws InterruptedException {
    	new HeapUsageTest();
        Thread.sleep(1000000);
    }

    private void printHeapUsage() {
        for (MemoryPoolMXBean mpbean :
             ManagementFactory.getMemoryPoolMXBeans()) {
            MemoryUsage usage = mpbean.getCollectionUsage();
            if (usage != null) {
                long max = usage.getMax();
                long used = usage.getUsed();            
                System.out.println(mpbean.getName() + " Used " + used + ", Max " + max);
            }
        }
		
    }
}

---------- END SOURCE ----------

FREQUENCY : always