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/* |
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* Written by Doug Lea 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.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.Condition; |
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import java.util.concurrent.locks.ReentrantLock; |
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|
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/** |
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* A variant of SimpleReentrantLockLoops that also has a very short timed wait. |
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* Demonstrates 2% performance improvement on x86 with weakened atomics in AQS. |
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*/ |
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public final class SimpleReentrantConditionWaitLoops { |
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static final ExecutorService pool = Executors.newCachedThreadPool(); |
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static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom(); |
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static final int ITERS = Integer.getInteger("iters", 2000000); |
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static final int MAX_THREADS = Integer.getInteger("maxThreads", 1); |
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static boolean print = false; |
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|
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public static void main(String[] args) throws Exception { |
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|
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new ReentrantConditionWaitLoop(1).test(); |
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new ReentrantConditionWaitLoop(1).test(); |
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print = true; |
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|
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for (int k = 1, i = 1; i <= MAX_THREADS;) { |
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System.out.print("Threads: " + i); |
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new ReentrantConditionWaitLoop(i).test(); |
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Thread.sleep(10); |
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if (i == k) { |
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k = i << 1; |
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i = i + (i >>> 1); |
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} |
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else |
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i = k; |
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} |
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pool.shutdown(); |
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if (!pool.awaitTermination(10, TimeUnit.SECONDS)) |
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throw new Error("pool failed to terminate!"); |
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} |
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|
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static final class ReentrantConditionWaitLoop implements Runnable { |
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private int v = rng.next(); |
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private volatile int result = 17; |
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private final ReentrantLock lock = new ReentrantLock(); |
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private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer(); |
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private final CyclicBarrier barrier; |
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private final int nthreads; |
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private volatile int readBarrier; |
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ReentrantConditionWaitLoop(int nthreads) { |
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this.nthreads = nthreads; |
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barrier = new CyclicBarrier(nthreads+1, timer); |
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} |
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|
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final void test() throws Exception { |
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for (int i = 0; i < nthreads; ++i) |
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pool.execute(this); |
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barrier.await(); |
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barrier.await(); |
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if (print) { |
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long time = timer.getTime(); |
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long tpi = time / ((long) ITERS * nthreads); |
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System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock"); |
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double secs = (double) time / 1000000000.0; |
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System.out.println("\t " + secs + "s run time"); |
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} |
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|
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int r = result; |
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if (r == 0) // avoid overoptimization |
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System.out.println("useless result: " + r); |
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} |
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|
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public final void run() { |
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final ReentrantLock lock = this.lock; |
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final Condition condition = lock.newCondition(); |
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try { |
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barrier.await(); |
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int sum = v + 1; |
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int x = 0; |
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int n = ITERS; |
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while (n-- > 0) { |
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lock.lock(); |
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condition.await(10, TimeUnit.NANOSECONDS); |
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int k = (sum & 3); |
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if (k > 0) { |
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x = v; |
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while (k-- > 0) |
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x = LoopHelpers.compute6(x); |
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v = x; |
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} |
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else x = sum + 1; |
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lock.unlock(); |
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if ((x += readBarrier) == 0) |
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++readBarrier; |
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for (int l = x & 7; l > 0; --l) |
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sum += LoopHelpers.compute6(sum); |
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} |
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barrier.await(); |
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result += sum; |
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} |
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catch (Exception ie) { |
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return; |
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} |
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} |
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} |
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|
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} |
