Reflection vs MethodHandle performance in Oracle JDK 7u7

[Ashwin Jayaprakash]

Hi, I was looking at the Java 7 InvokeDynamic/MethodHandle feature set and
I was curious to know how it performed compared to good old Reflection.

I had refrained from posting this question for some time but I couldn't
wait any longer after I saw a reference to this bug fix
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7023639 (Bug ID: 7023639
JSR 292 method handle invocation needs a fast path for compiled code) on
this forum. I suppose this change will go into the Oracle JDK sometime
later.

I still went ahead with Oracle JDK 7u7 and ran a simple test using Google
Caliper (http://code.google.com/p/caliper/) on a Win 7, 64bit, 1 cpu x 2
core x 4 HT, i7 920 laptop.

*Q1: *MethodHandle still seems slower than Reflection. Will that change
sometime in the future?

*Q2: *Also, am I using MethodHandle the right way in the code
Temp::timeHandle(int) below?

Test results:
 0% Scenario{vm=java, trial=0, benchmark=Reflect, serverMode=-server,
memoryMin=-Xmx96M, memoryMax=-Xmx96M} 16.76 ns; ?=0.18 ns @ 10 trials
20% Scenario{vm=java, trial=0, benchmark=Handle, serverMode=-server,
memoryMin=-Xmx96M, memoryMax=-Xmx96M} 21.98 ns; ?=0.57 ns @ 10 trials
40% Scenario{vm=java, trial=0, benchmark=Direct, serverMode=-server,
memoryMin=-Xmx96M, memoryMax=-Xmx96M} 4.93 ns; ?=0.06 ns @ 10 trials
60% Scenario{vm=java, trial=0, benchmark=Iface, serverMode=-server,
memoryMin=-Xmx96M, memoryMax=-Xmx96M} 4.94 ns; ?=0.30 ns @ 10 trials
80% Scenario{vm=java, trial=0, benchmark=Static, serverMode=-server,
memoryMin=-Xmx96M, memoryMax=-Xmx96M} 4.88 ns; ?=0.03 ns @ 3 trials

benchmark    ns linear runtime
  Reflect 16.76 ======================
   Handle 21.98 ==============================
   Direct  4.93 ======
    Iface  4.94 ======
   Static  4.88 ======

vm: java
trial: 0
serverMode: -server
memoryMin: -Xmx96M
memoryMax: -Xmx96M


Test code:
public class Temp extends SimpleBenchmark {
    public static void main(String[] args) throws Exception {
        Runner.main(Temp.class, args);
    }

    public void timeReflect(int reps) throws Exception {
        Method m = K.class.getMethod("exec", Object.class);

        K k = new K();

        for (int i = 0; i < reps; i++) {
            m.invoke(k, i);
        }
    }

    public void timeHandle(int reps) throws Throwable {
        MethodHandle mh = MethodHandles.lookup().findVirtual(K.class,
"exec", MethodType.methodType(void.class, Object.class));

        K k = new K();

        for (int i = 0; i < reps; i++) {
            mh.invokeExact(k, (Object) i);
        }
    }

    public void timeDirect(int reps) throws Exception {
        Method m = K.class.getMethod("exec", Object.class);

        K k = new K();

        for (int i = 0; i < reps; i++) {
            k.exec(i);
        }
    }

    public void timeIface(int reps) throws Exception {
        M m = new K();

        for (int i = 0; i < reps; i++) {
            m.exec(i);
        }
    }

    public void timeStatic(int reps) throws Exception {
        for (int i = 0; i < reps; i++) {
            K.execS(i);
        }
    }
}

public class K implements M {
    static long s = 0;

    long l = 0;

    @Override
    public void exec(Object o) {
        l += o.hashCode();
    }

    public static void execS(Object o) {
        s += o.hashCode();
    }
}

public interface M {
    void exec(Object o);
}

Thanks,
Ashwin (http://www.ashwinjayaprakash.com).
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