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root/jsr166/jsr166/src/test/loops/NoopSpinLockLoops.java
Revision: 1.10
Committed: Sat Dec 31 22:17:40 2016 UTC (7 years, 2 months ago) by jsr166
Branch: MAIN
CVS Tags: HEAD
Changes since 1.9: +0 -1 lines
Log Message:
organize imports

File Contents

# Content
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 import java.util.concurrent.atomic.AtomicInteger;
11
12 public final class NoopSpinLockLoops {
13 static final ExecutorService pool = Executors.newCachedThreadPool();
14 static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
15 static boolean print = false;
16 static int iters = 20000000;
17
18 public static void main(String[] args) throws Exception {
19 int maxThreads = 100;
20 if (args.length > 0)
21 maxThreads = Integer.parseInt(args[0]);
22
23 new ReentrantLockLoop(1).test();
24 new ReentrantLockLoop(1).test();
25 print = true;
26
27 for (int k = 1, i = 1; i <= maxThreads;) {
28 System.out.print("Threads: " + i);
29 new ReentrantLockLoop(i).test();
30 Thread.sleep(100);
31 if (i == k) {
32 k = i << 1;
33 i = i + (i >>> 1);
34 }
35 else
36 i = k;
37 }
38 pool.shutdown();
39 }
40
41 static final class ReentrantLockLoop implements Runnable {
42 private int v = rng.next();
43 private volatile int result = 17;
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 private final AtomicInteger spinlock = new AtomicInteger();
49 ReentrantLockLoop(int nthreads) {
50 this.nthreads = nthreads;
51 barrier = new CyclicBarrier(nthreads+1, timer);
52 }
53
54 final void test() throws Exception {
55 for (int i = 0; i < nthreads; ++i)
56 pool.execute(this);
57 barrier.await();
58 barrier.await();
59 if (print) {
60 long time = timer.getTime();
61 long tpi = time / ((long) iters * nthreads);
62 System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
63 double secs = (double) time / 1000000000.0;
64 System.out.println("\t " + secs + "s run time");
65 }
66
67 int r = result;
68 if (r == 0) // avoid overoptimization
69 System.out.println("useless result: " + r);
70 }
71
72 public final void run() {
73 final AtomicInteger lock = this.spinlock;
74 try {
75 barrier.await();
76 int sum = v + 1;
77 int x = sum + 1;
78 int n = iters;
79 while (n-- > 0) {
80 do {} while (!lock.compareAndSet(0, 1));
81 x = LoopHelpers.compute4(x);
82 lock.set(0);
83 if ((x += readBarrier) == 0)
84 ++readBarrier;
85
86 sum += x;
87 }
88 barrier.await();
89 result += sum;
90 }
91 catch (Exception ie) {
92 return;
93 }
94 }
95 }
96
97 }