| 1 |
/* |
| 2 |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
| 3 |
* Expert Group and released to the public domain, as explained at |
| 4 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
| 5 |
*/ |
| 6 |
|
| 7 |
import java.util.concurrent.CyclicBarrier; |
| 8 |
import java.util.concurrent.ExecutorService; |
| 9 |
import java.util.concurrent.Executors; |
| 10 |
|
| 11 |
public final class SimpleLockLoops { |
| 12 |
static final ExecutorService pool = Executors.newCachedThreadPool(); |
| 13 |
static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom(); |
| 14 |
static boolean print = false; |
| 15 |
static int iters = 2000000; |
| 16 |
|
| 17 |
public static void main(String[] args) throws Exception { |
| 18 |
int maxThreads = 100; |
| 19 |
if (args.length > 0) |
| 20 |
maxThreads = Integer.parseInt(args[0]); |
| 21 |
|
| 22 |
new LockLoop(1).test(); |
| 23 |
new LockLoop(1).test(); |
| 24 |
print = true; |
| 25 |
|
| 26 |
for (int k = 1, i = 1; i <= maxThreads;) { |
| 27 |
System.out.print("Threads: " + i); |
| 28 |
new LockLoop(i).test(); |
| 29 |
Thread.sleep(100); |
| 30 |
if (i == k) { |
| 31 |
k = i << 1; |
| 32 |
i = i + (i >>> 1); |
| 33 |
} |
| 34 |
else |
| 35 |
i = k; |
| 36 |
} |
| 37 |
pool.shutdown(); |
| 38 |
} |
| 39 |
|
| 40 |
static final class LockLoop implements Runnable { |
| 41 |
private int v = rng.next(); |
| 42 |
private volatile int result = 17; |
| 43 |
private final Object lock = new Object(); |
| 44 |
private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer(); |
| 45 |
private final CyclicBarrier barrier; |
| 46 |
private final int nthreads; |
| 47 |
private volatile int readBarrier; |
| 48 |
LockLoop(int nthreads) { |
| 49 |
this.nthreads = nthreads; |
| 50 |
barrier = new CyclicBarrier(nthreads+1, timer); |
| 51 |
} |
| 52 |
|
| 53 |
final void test() throws Exception { |
| 54 |
for (int i = 0; i < nthreads; ++i) |
| 55 |
pool.execute(this); |
| 56 |
barrier.await(); |
| 57 |
barrier.await(); |
| 58 |
if (print) { |
| 59 |
long time = timer.getTime(); |
| 60 |
long tpi = time / ((long) iters * nthreads); |
| 61 |
System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock"); |
| 62 |
double secs = (double) time / 1000000000.0; |
| 63 |
System.out.println("\t " + secs + "s run time"); |
| 64 |
} |
| 65 |
|
| 66 |
int r = result; |
| 67 |
if (r == 0) // avoid overoptimization |
| 68 |
System.out.println("useless result: " + r); |
| 69 |
} |
| 70 |
|
| 71 |
public final void run() { |
| 72 |
final Object lock = this.lock; |
| 73 |
try { |
| 74 |
barrier.await(); |
| 75 |
int sum = v + 1; |
| 76 |
int x = 0; |
| 77 |
int n = iters; |
| 78 |
while (n-- > 0) { |
| 79 |
synchronized (lock) { |
| 80 |
int k = (sum & 3); |
| 81 |
if (k > 0) { |
| 82 |
x = v; |
| 83 |
while (k-- > 0) |
| 84 |
x = LoopHelpers.compute6(x); |
| 85 |
v = x; |
| 86 |
} |
| 87 |
else x = sum + 1; |
| 88 |
} |
| 89 |
if ((x += readBarrier) == 0) |
| 90 |
++readBarrier; |
| 91 |
for (int l = x & 7; l > 0; --l) |
| 92 |
sum += LoopHelpers.compute6(sum); |
| 93 |
} |
| 94 |
barrier.await(); |
| 95 |
result += sum; |
| 96 |
} |
| 97 |
catch (Exception ie) { |
| 98 |
return; |
| 99 |
} |
| 100 |
} |
| 101 |
} |
| 102 |
|
| 103 |
} |
