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/* |
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* Written by Martin Buchholz with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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import java.util.Collections; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.CyclicBarrier; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Executors; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.locks.ReentrantLock; |
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|
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/** |
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* Measures repeated futile timed attempts to acquire a ReentrantLock. |
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* Hard to draw any conclusions from. |
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*/ |
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public final class FutileTimedTryLockLoops { |
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|
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static Callable<Void> tryLocker(ReentrantLock lock, long iters, long nanos) { |
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return new Callable<Void>() { |
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public Void call() throws InterruptedException { |
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for (long i = 0; i < iters; i++) |
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if (lock.tryLock(nanos, TimeUnit.NANOSECONDS)) |
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throw new AssertionError(); |
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return null; |
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}}; |
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} |
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|
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public static void main(String[] args) throws Exception { |
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int minThreads = 1; |
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int maxThreads = 4; |
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long nanos = 1001L; |
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long iters = 60_000_000L; |
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nextArg: for (String arg : args) { |
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String[] fields = arg.split("="); |
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if (fields.length == 2) { |
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String prop = fields[0], val = fields[1]; |
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switch (prop) { |
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case "threads": |
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minThreads = maxThreads = Integer.valueOf(val); |
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continue nextArg; |
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case "minThreads": |
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minThreads = Integer.valueOf(val); |
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continue nextArg; |
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case "maxThreads": |
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maxThreads = Integer.valueOf(val); |
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continue nextArg; |
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case "nanos": |
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nanos = Long.valueOf(val); |
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continue nextArg; |
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case "iters": |
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iters = Long.valueOf(val); |
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continue nextArg; |
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} |
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} |
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throw new Error("Usage: FutileTimedTryLockLoops minThreads=n maxThreads=n threads=n nanos=n iters=n"); |
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} |
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final ExecutorService pool = Executors.newCachedThreadPool(); |
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final ReentrantLock lock = new ReentrantLock(); |
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final Callable<Void> task = tryLocker(lock, iters, nanos); |
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lock.lock(); |
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|
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for (int i = minThreads; i <= maxThreads; i += (i+1) >>> 1) { |
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// warmup |
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if (i == minThreads) |
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pool.invokeAll(Collections.nCopies(i, task)); |
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|
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long startTime = System.nanoTime(); |
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pool.invokeAll(Collections.nCopies(i, task)); |
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long elapsed = System.nanoTime() - startTime; |
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System.out.printf |
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("Threads: %d, %d ms total, %d ns/iter, overhead %d ns/iter%n", |
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i, |
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elapsed / (1000*1000), |
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elapsed / iters, |
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(elapsed / iters) - nanos); |
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} |
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pool.shutdown(); |
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} |
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} |
