Created
September 29, 2011 10:43
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Fairness of ReentrantLock performance test
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import java.text.NumberFormat; | |
import java.util.LinkedList; | |
import java.util.List; | |
import java.util.concurrent.atomic.AtomicInteger; | |
import java.util.concurrent.locks.ReentrantLock; | |
/** | |
* @author slukjanov aka Frostman | |
*/ | |
public class FairnessPerformanceTest { | |
private static final AtomicInteger WORKERS_COUNT = new AtomicInteger(); | |
private static final NumberFormat NF = getNumberFormat(); | |
private final ReentrantLock lock; | |
private final int maxAcquires; | |
private int totalAcquires = 0; | |
public static void main(String[] args) { | |
boolean badArgs = true, fair = false; | |
int threads = 0, maxAcquires = 0; | |
if (args.length == 3) { | |
try { | |
threads = Integer.parseInt(args[0]); | |
maxAcquires = Integer.parseInt(args[1]); | |
fair = Boolean.parseBoolean(args[2]); | |
} catch (Exception e) { | |
System.err.println(e.getMessage()); | |
} | |
badArgs = false; | |
} | |
if (badArgs) { | |
System.err.println("Mandatory args: THREADS MAX_ACQUIRES FAIRNESS"); | |
System.exit(1); | |
} | |
new FairnessPerformanceTest(threads, maxAcquires, fair); | |
} | |
public FairnessPerformanceTest(int threads, int maxAcquires, boolean fair) { | |
lock = new ReentrantLock(fair); | |
this.maxAcquires = maxAcquires; | |
System.out.println("FairnessPerformanceTest: " + (fair ? "" : "non-") + "fair lock"); | |
System.out.println("Warming up"); | |
test(threads * 2, true); | |
System.out.println("Start testing:"); | |
test(threads, false); | |
} | |
private void test(int threads, boolean silent) { | |
totalAcquires = 0; | |
WORKERS_COUNT.set(0); | |
long start = System.nanoTime(); | |
Worker[] workers = new Worker[threads]; | |
for (int i = 0; i < threads; i++) { | |
workers[i] = new Worker(); | |
workers[i].start(); | |
} | |
List<Double> deviations = new LinkedList<Double>(); | |
for (Worker worker : workers) { | |
try { | |
worker.join(); | |
} catch (InterruptedException e) { | |
throw new RuntimeException("Worker#join interrupted, id: " + worker.id, e); | |
} | |
if (!silent) { | |
double percents = 1.0 * worker.acquires / totalAcquires * 100; | |
double deviation = Math.abs(100.0 / threads - percents); | |
deviations.add(deviation); | |
System.out.println("Worker#" + worker.id + " acquires: " + NF.format(percents) + "%" | |
+ " deviation: " + NF.format(deviation) + "%"); | |
} | |
} | |
if (!silent) { | |
double maxDeviation = 0; | |
double minDeviation = 100; | |
double averageDeviation = 0; | |
for (Double deviation : deviations) { | |
maxDeviation = Math.max(maxDeviation, deviation); | |
minDeviation = Math.min(minDeviation, deviation); | |
averageDeviation += deviation; | |
} | |
averageDeviation /= threads; | |
System.out.println("\nDeviation:\n\tmax: " + NF.format(maxDeviation) + "%\n\tavg: " | |
+ NF.format(averageDeviation) + "%\n\tmin: " + NF.format(minDeviation) + "%"); | |
System.out.println("Takes " + (System.nanoTime() - start) / 1000000 + "ms"); | |
} | |
} | |
private class Worker extends Thread { | |
private int id = WORKERS_COUNT.getAndIncrement(); | |
private int acquires = 0; | |
@Override | |
public void run() { | |
while (true) { | |
lock.lock(); | |
try { | |
if (totalAcquires == maxAcquires) { | |
return; | |
} | |
acquires++; | |
totalAcquires++; | |
} finally { | |
lock.unlock(); | |
} | |
} | |
} | |
} | |
private static NumberFormat getNumberFormat() { | |
NumberFormat nf = NumberFormat.getInstance(); | |
nf.setMinimumFractionDigits(4); | |
nf.setMaximumFractionDigits(4); | |
nf.setMaximumIntegerDigits(2); | |
return nf; | |
} | |
} |
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