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.*; |
8 |
import java.util.concurrent.*; |
9 |
import java.util.concurrent.locks.*; |
10 |
|
11 |
public final class NoopLockLoops { |
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 = 20000000; |
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 ReentrantLockLoop(1).test(); |
23 |
new ReentrantLockLoop(1).test(); |
24 |
print = true; |
25 |
|
26 |
for (int k = 1, i = 1; i <= maxThreads;) { |
27 |
System.out.print("Threads: " + i); |
28 |
new ReentrantLockLoop(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 ReentrantLockLoop implements Runnable { |
41 |
private int v = rng.next(); |
42 |
private volatile int result = 17; |
43 |
private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer(); |
44 |
private final CyclicBarrier barrier; |
45 |
private final int nthreads; |
46 |
private volatile int readBarrier; |
47 |
ReentrantLockLoop(int nthreads) { |
48 |
this.nthreads = nthreads; |
49 |
barrier = new CyclicBarrier(nthreads+1, timer); |
50 |
} |
51 |
|
52 |
final void test() throws Exception { |
53 |
for (int i = 0; i < nthreads; ++i) |
54 |
pool.execute(this); |
55 |
barrier.await(); |
56 |
barrier.await(); |
57 |
if (print) { |
58 |
long time = timer.getTime(); |
59 |
long tpi = time / ((long) iters * nthreads); |
60 |
System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock"); |
61 |
double secs = (double) time / 1000000000.0; |
62 |
System.out.println("\t " + secs + "s run time"); |
63 |
} |
64 |
|
65 |
int r = result; |
66 |
if (r == 0) // avoid overoptimization |
67 |
System.out.println("useless result: " + r); |
68 |
} |
69 |
|
70 |
public final void run() { |
71 |
try { |
72 |
barrier.await(); |
73 |
int sum = v + 1; |
74 |
int x = sum + 1; |
75 |
int n = iters; |
76 |
while (n-- > 0) { |
77 |
synchronized (this) { |
78 |
x = LoopHelpers.compute4(x); |
79 |
} |
80 |
sum += x; |
81 |
if ((x += readBarrier) == 0) |
82 |
++readBarrier; |
83 |
} |
84 |
barrier.await(); |
85 |
result += sum; |
86 |
} |
87 |
catch (Exception ie) { |
88 |
return; |
89 |
} |
90 |
} |
91 |
} |
92 |
|
93 |
} |