import java.io.*;
import java.nio.*;


public class BufferPutSpeed {

    static PrintStream log = System.out;

    static final int N = 100;

    static String type(ByteBuffer b) {
	return b.isDirect() ? "dir" : "heap";
    }

    static void go(ByteBuffer src, ByteBuffer dst) {
	log.print(type(src) + " --> " + type(dst) + "\t");
	long start = System.currentTimeMillis();
	for (int i = 0; i < N; i++) {
	    src.clear();
	    dst.clear();
	    dst.put(src);
	}
	log.println(System.currentTimeMillis() - start);
    }

    public static void main(String[] args) {
	ByteBuffer bbh1 = ByteBuffer.allocate(1 << 20);
	ByteBuffer bbh2 = ByteBuffer.allocate(1 << 20);
	ByteBuffer bbd1 = ByteBuffer.allocateDirect(1 << 20);
	ByteBuffer bbd2 = ByteBuffer.allocateDirect(1 << 20);
	go(bbd1, bbd2);
	go(bbd1, bbh1);
	go(bbh1, bbd1);
	go(bbh1, bbh2);
    }

}


% jr BufferPutSpeed
dir --> dir     412
dir --> heap    3802
heap --> dir    4360
heap --> heap   411
% 

In addition to slowing down pure buffer operations, this discrepancy is also
visible when doing channel reads and writes with non-direct buffers.

-- ###@###.### 2002/4/29