Direct Memory vs On Heap in Java

gistfile1.java

import java.nio.ByteBuffer;
import java.util.Random;

public class BufferPerformanceComparison {
	public final static int MEGA_BYTE = 1024 * 1024;
	public final static long GIGA_BYTE = MEGA_BYTE * 1024;
	private final ByteBuffer heapByteBuffer;
	private final ByteBuffer offHeapByteBuffer;
	private final long dataToLoad;
	private final int bufferSize;
	private final Random random = new Random();
	private final byte[] base = "I've heard direct buffers are really slow. Are they right or are they wrong. Because if they are right I want to be careful using them and if they are wrong I want to leverage them when I can."
			.getBytes();

	public BufferPerformanceComparison(int bufferSize, long dataToLoad) {
		this.heapByteBuffer = ByteBuffer.allocate(bufferSize);
		this.offHeapByteBuffer = ByteBuffer.allocateDirect(bufferSize);
		this.dataToLoad = dataToLoad;
		this.bufferSize = bufferSize;
	}

	public void start() {
		for (int round = 0; round < 4; round++) {
			boolean isWarmup = round == 0;
			loadByteBuffer(heapByteBuffer, dataToLoad, !isWarmup, "ONHEAP");
			loadByteBuffer(offHeapByteBuffer, dataToLoad, !isWarmup, "DIRECT");
		}

	}

	private void loadByteBuffer(ByteBuffer byteBuffer, long dataToLoad,
			boolean printResults, String type) {
		long bytesWritten = 0;
		long start = System.currentTimeMillis();
		int writePosition = random.nextInt(bufferSize - (base.length + 1));
		int readPosition = random.nextInt(bufferSize - (base.length + 1));
		byte[] readArray = new byte[base.length];
		int count = 0;
		while (bytesWritten < dataToLoad) {
			count++;
			if (count % 10 == 0) {
				writePosition = random.nextInt(bufferSize - (base.length + 1));
			}
			bytesWritten += base.length;
			byteBuffer.position(writePosition);
			byteBuffer.put(base);
			byteBuffer.position(readPosition);
			byteBuffer.get(readArray, 0, base.length);
		}
		if (printResults)
			System.out.println("Type: " + type + " Took: "
					+ (System.currentTimeMillis() - start) + " to write and read: "
					+ bytesWritten);

	}

	public static void main(String[] args) throws Exception {
		new BufferPerformanceComparison(50 * MEGA_BYTE, 10L * GIGA_BYTE)
				.start();
	}

}


/// Output for 1.6 ghz notebook ///


Type: ONHEAP Took: 8978 to write and read: 10737418368
Type: DIRECT Took: 9223 to write and read: 10737418368
Type: ONHEAP Took: 8827 to write and read: 10737418368
Type: DIRECT Took: 9283 to write and read: 10737418368
Type: ONHEAP Took: 8813 to write and read: 10737418368
Type: DIRECT Took: 9604 to write and read: 10737418368