今天在处理问题时候,采用了读写锁,之前印象中记得读写锁在读大于写的场景下效率会比较高,但是并不是很明确,所以就乘机测试。具体测试代码如下所示:
package com.zhaming.lock; import java.util.Random; <em id="__mceDel">import java.util.concurrent.CountDownLatch; import java.util.concurrent.CyclicBarrier; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantLock; import java.util.concurrent.locks.ReentrantReadWriteLock;</em> public class ConcurrentObject { private static Random random = new Random(); private final static int READ_NUM = 100; private final static int WRITE_NUM = 100; private int value; private ReadWriteLock lock = new ReentrantReadWriteLock(); private Lock locknew = new ReentrantLock(); public static void main(String[] args) throws InterruptedException { // int maxProcessor = Runtime.getRuntime().availableProcessors() * 2; 防止线程池大小过大,CPU过多的上下文切换导致的开销影响 int maxProcessor = READ_NUM + WRITE_NUM;// 线程池大小必须同 总共开启的对象 final ExecutorService newFixedThreadPool = Executors.newFixedThreadPool(maxProcessor); final CountDownLatch latch = new CountDownLatch(READ_NUM + WRITE_NUM);// 最后关闭线程池 final CyclicBarrier barrier = new CyclicBarrier(READ_NUM + WRITE_NUM);// 等待所有线程启动后并发读写 final ConcurrentObject concurrentObject = new ConcurrentObject(); for (int i = 0; i < READ_NUM; i++) { newFixedThreadPool.execute(new Runnable() { @Override public void run() { try { barrier.await(); } catch (Exception e) { e.printStackTrace(); } TimeCostUtils.start(TimeCostUtils.READ); concurrentObject.getValueLock(); TimeCostUtils.end(); latch.countDown(); } }); } for (int i = 0; i < WRITE_NUM; i++) { newFixedThreadPool.execute(new Runnable() { @Override public void run() { int nextInt = random.nextInt(1000); try { barrier.await(); } catch (Exception e) { e.printStackTrace(); } TimeCostUtils.start(TimeCostUtils.WRITE); concurrentObject.setValueLock(nextInt); TimeCostUtils.end(); latch.countDown(); } }); } latch.await(); newFixedThreadPool.shutdown(); // 系统推出前,关闭线程池及计算平均耗时、总耗时 Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() { @Override public void run() { display(); } })); } public static void display() { System.out.println("read cost average:" + (TimeCostUtils.getReadLong().get() / READ_NUM) + " ns"); System.out.println("write cost average:" + (TimeCostUtils.getWriteLong().get() / WRITE_NUM) + " ns"); } public int getValue() { lock.readLock().lock(); try { return value; } finally { lock.readLock().unlock(); } } public void setValue(int value) { locknew.lock(); try { this.value = value; } finally { locknew.unlock(); } } public int getValueLock() { locknew.lock(); try { return value; } finally { locknew.unlock(); } } public void setValueLock(int value) { lock.writeLock().lock(); try { this.value = value; } finally { lock.writeLock().unlock(); } } public synchronized int getValueSyn() { return value; } public synchronized void setValueSyn(int value) { this.value = value; } } 辅助工具类: package com.zhaming.lock; import java.util.concurrent.atomic.AtomicLong; public class TimeCostUtils { private static AtomicLong readLong = new AtomicLong(); private static AtomicLong writeLong = new AtomicLong(); public final static String WRITE = "write"; public final static String READ = "read"; static ThreadLocal<TimesRecords> recordMap = new ThreadLocal<TimesRecords>(); public static void start(String prefix) { TimesRecords timesRecords = new TimesRecords(prefix, System.nanoTime()); recordMap.set(timesRecords); } public static void end() { TimesRecords timesRecords = recordMap.get(); long cost = System.nanoTime() - timesRecords.getCost(); // 计算每次的开销时间 if (timesRecords.getName().equals(WRITE)) { writeLong.addAndGet(cost); } else { readLong.addAndGet(cost); } } public static AtomicLong getReadLong() { return readLong; } public static AtomicLong getWriteLong() { return writeLong; } static class TimesRecords { private String name; private long cost; public TimesRecords(String name, long cost) { this.name = name; this.cost = cost; } public String getName() { return name; } public void setName(String name) { this.name = name; } public long getCost() { return cost; } public void setCost(long cost) { this.cost = cost; } } }
测试的JDK版本:
java version “1.6.0_29”
Java(TM) SE Runtime Environment (build 1.6.0_29-b11)
Java HotSpot(TM) 64-Bit Server VM (build 20.4-b02, mixed mode)
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