互斥锁读取与顺序读取性能比较

package concurrencyTest;

import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.hama.graph.GraphJobMessage;


public class ConcurrencyReadTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		ConcurrentHashMap<Integer, Integer>  map = new ConcurrentHashMap<Integer, Integer>() ;
		for(int i=0;i<100000 ; i++)
			map.put(i, i+111111) ;
		
		long start = System.currentTimeMillis() ;
		Thread t1 = new Thread(new Worker(map)) ;
		Thread t2 = new Thread(new Worker(map)) ;
		
		t1.start(); 
		t2.start();
		
		try {
			t1.join() ;
			t2.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("Read last : " + (System.currentTimeMillis() - start) + " ms");
	}

	
}

class Worker implements Runnable {
	ConcurrentHashMap<Integer, Integer>  sharemap ;
	public static Object mutex = new Object() ;
	
	public Worker(ConcurrentHashMap<Integer, Integer> map) {
		sharemap = map ;
	}
	
	@Override
	public void run() {
		 it = sharemap.values().iterator();
		 Integer i = poll(); 
		 while(i!=null) {
			 int k = i ;
			 i = poll() ;
		 }
	}
	

	Iterator<Integer> it;

	public Integer poll() {
		synchronized (mutex) {
		     if (sharemap.size() > 0 && it!=null && it.hasNext()) {
		         Integer m = it.next();
		         it.remove();
		         return m;
		       } else {
		         return null;
		       }
		}
	}
}

顺序:

46
46
47

并发
63
78
63

增大到100万条数据:

并发

312
312
327

顺序
188
187
187

可见锁对性能影响之大！