Executor并发性能对比

<span style="font-family: Arial, Helvetica, sans-serif;">import java.util.ArrayList;</span>

import java.util.List;import java.util.concurrent.Callable;import java.util.concurrent.CompletionService;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ConcurrentLinkedQueue;import java.util.concurrent.ExecutorCompletionService;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import java.util.concurrent.RejectedExecutionHandler;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;import org.apache.hadoop.io.IntWritable;public class ArrayTest {public static void main(String[] args) {long start = System.currentTimeMillis() ;ArrayTest blt = new ArrayTest() ;List<IntWritable> messages = new ArrayList<IntWritable>();for(int i =0 ;i<10000; i++) { messages.add(new IntWritable(i)) ;}//RejectedExecutionHandler retryHandler = new RetryRejectedExecutionHandler();//    ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors//            .newCachedThreadPool();//    executor.setMaximumPoolSize(64);//    executor.setRejectedExecutionHandler(retryHandler);//    //     for (IntWritable i : messages) {//        executor.execute(blt.new Worker(i));//      }////      executor.shutdown();//      try {//        executor.awaitTermination(60, TimeUnit.SECONDS);//      } catch (Exception e) {//        e.printStackTrace() ;//      }ExecutorService pool = Executors.newCachedThreadPool(); // 并发测试CompletionService<Boolean> exchangeResult = new ExecutorCompletionService<Boolean>(pool);int destSize = 0;for(IntWritable i : messages) {exchangeResult.submit(blt.new Worker(i));destSize++;}int count = 0;while (count < destSize) {Future<Boolean> f = exchangeResult.poll();if (f == null)continue;count++ ;}    try {pool.awaitTermination(60, TimeUnit.SECONDS);} catch (Throwable e) {e.printStackTrace();}System.out.println("Last " + (System.currentTimeMillis() - start) + " ms");}  class Worker implements  Callable<Boolean> {IntWritable msg;public Worker(IntWritable msg) {this.msg = msg;}@Overridepublic Boolean call() throws Exception {try { int sum = msg.get() ;} catch (Exception e) {e.printStackTrace() ;}return true;}}//  class Worker implements  Runnable {//IntWritable msg;////public Worker(IntWritable msg) {//this.msg = msg;//}////@Override//public void run() {//try {// int sum = msg.get() ;//} catch (Exception e) {//e.printStackTrace() ;//}//}//}  }class RetryRejectedExecutionHandler implements RejectedExecutionHandler {    @Override    public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {      try {        Thread.sleep(10);      } catch (InterruptedException e) {        e.printStackTrace() ;      }      executor.execute(r);    }}

第一种:  Last 60186 ms

第二种:

package concurrencyTest;import java.util.ArrayList;import java.util.List;import java.util.concurrent.Callable;import java.util.concurrent.CompletionService;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ConcurrentLinkedQueue;import java.util.concurrent.ExecutorCompletionService;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import java.util.concurrent.RejectedExecutionHandler;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;import org.apache.hadoop.io.IntWritable;public class ArrayTest {public static void main(String[] args) {long start = System.currentTimeMillis() ;ArrayTest blt = new ArrayTest() ;List<IntWritable> messages = new ArrayList<IntWritable>();for(int i =0 ;i<10000; i++) { messages.add(new IntWritable(i)) ;}RejectedExecutionHandler retryHandler = new RetryRejectedExecutionHandler();    ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors            .newCachedThreadPool();    executor.setMaximumPoolSize(64);    executor.setRejectedExecutionHandler(retryHandler);         for (IntWritable i : messages) {        executor.execute(blt.new Worker(i));      }      executor.shutdown();      try {        executor.awaitTermination(60, TimeUnit.SECONDS);      } catch (Exception e) {        e.printStackTrace() ;      }//ExecutorService pool = Executors.newCachedThreadPool(); // 并发测试//CompletionService<Boolean> exchangeResult = new ExecutorCompletionService<Boolean>(//pool);//int destSize = 0;//for(IntWritable i : messages) {//exchangeResult.submit(blt.new Worker(i));//destSize++;//}////int count = 0;//while (count < destSize) {//Future<Boolean> f = exchangeResult.poll();//if (f == null)//continue;//count++ ;//}//    try {//pool.awaitTermination(60, TimeUnit.SECONDS);//} catch (Throwable e) {//e.printStackTrace();//}System.out.println("Last " + (System.currentTimeMillis() - start) + " ms");}//  class Worker implements  Callable<Boolean> {//IntWritable msg;////public Worker(IntWritable msg) {//this.msg = msg;//}////@Override//public Boolean call() throws Exception {//try {// int sum = msg.get() ;//} catch (Exception e) {//e.printStackTrace() ;//}//return true;//}//}  class Worker implements  Runnable {IntWritable msg;public Worker(IntWritable msg) {this.msg = msg;}@Overridepublic void run() {try { int sum = msg.get() ;} catch (Exception e) {e.printStackTrace() ;}}}  }class RetryRejectedExecutionHandler implements RejectedExecutionHandler {    @Override    public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {      try {        Thread.sleep(10);      } catch (InterruptedException e) {        e.printStackTrace() ;      }      executor.execute(r);    }}

 
 Last 271 ms
 
 可能是前一种写法有问题，导致性能很差，但是奇怪没有报错！

第一种写法，即使用 Callable<Boolean>在线程数较少时(<100)，没有问题，但是线程数较大，如100,000,则会由于资源不足而阻塞，性能急剧降低。
第二种写法则不存在此问题。