Biased Locking in Java SE 6

key

之前一直没有注意到Biased Locking的存在。刚刚做了一下实验，的确如此。
下面是程序实验及相关的出处。不过我把程序小改了一下。

1. 参考文章出处：http://ceki.blogspot.com/2009/06 ... -in-java-se-60.html
2. 输出结果：

1. $ java LockingInJava2
   
2. java.runtime.version = 1.6.0_21-b06
   
3. java.vendor          = Sun Microsystems Inc.
   
4. java.version         = 1.6.0_21
   
5. os.name              = Linux
   
6. os.version           = 2.6.32-24-generic
   
7. lock creator = Thread-0
   
8. runnable[0]: thread name = Thread-0, counter=467
   
9. runnable[1]: thread name = Thread-1, counter=47
   
10. runnable[2]: thread name = Thread-2, counter=152
    
11. runnable[3]: thread name = Thread-3, counter=326
    
12. runnable[4]: thread name = Thread-4, counter=2

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3. 输出结果2：

1. $ java -XX:-UseBiasedLocking LockingInJava2
   
2. java.runtime.version = 1.6.0_21-b06
   
3. java.vendor          = Sun Microsystems Inc.
   
4. java.version         = 1.6.0_21
   
5. os.name              = Linux
   
6. os.version           = 2.6.32-24-generic
   
7. lock creator = Thread-0
   
8. runnable[0]: thread name = Thread-0, counter=250
   
9. runnable[1]: thread name = Thread-1, counter=60
   
10. runnable[2]: thread name = Thread-2, counter=71
    
11. runnable[3]: thread name = Thread-3, counter=99
    
12. runnable[4]: thread name = Thread-4, counter=514

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4. 参考程序（我修改过的版本）

1. public class LockingInJava2 implements Runnable {
   
2. 
   
3. static int THREAD_COUNT = 5;
   
4. //static Object LOCK = new Object();
   
5. static Object LOCK = null;
   
6. static Runnable[] RUNNABLE_ARRAY = new Runnable[THREAD_COUNT];
   
7. static Thread[] THREAD_ARRAY = new Thread[THREAD_COUNT];
   
8. static String LOCK_CREATOR = null;
   
9. 
   
10. private int counter = 0;
    
11. private String threadId;
    
12. 
    
13. public static void main(String args[]) throws InterruptedException {
    
14.    printEnvironmentInfo();
    
15.    execute();
    
16.    printResults();
    
17. }
    
18. 
    
19. /**
    
20.   * Try to create a biased lock
    
21.   */
    
22. public synchronized static Object getLock() {
    
23.         if(LOCK == null){
    
24.                 LOCK = new Object();
    
25.                 LOCK_CREATOR = Thread.currentThread().getName();
    
26.         }
    
27.         return LOCK;
    
28. }
    
29. 
    
30. public static void printEnvironmentInfo() {
    
31.    System.out.println("java.runtime.version = "
    
32.        + System.getProperty("java.runtime.version"));
    
33.    System.out.println("java.vendor          = "
    
34.        + System.getProperty("java.vendor"));
    
35.    System.out.println("java.version         = "
    
36.        + System.getProperty("java.version"));
    
37.    System.out.println("os.name              = "
    
38.        + System.getProperty("os.name"));
    
39.    System.out.println("os.version           = "
    
40.        + System.getProperty("os.version"));
    
41. }
    
42. 
    
43. public static void execute() throws InterruptedException {
    
44.     for (int i = 0; i < THREAD_COUNT; i++) {
    
45.       RUNNABLE_ARRAY[i] = new LockingInJava2();
    
46.       THREAD_ARRAY[i] = new Thread(RUNNABLE_ARRAY[i]);
    
47.     }
    
48.     for (Thread t : THREAD_ARRAY) {
    
49.       t.start();
    
50.     }
    
51.     // let the threads run for a while
    
52.     Thread.sleep(10000);
    
53. 
    
54.     for (int i = THREAD_COUNT - 1; i >= 0; i--) {
    
55.       THREAD_ARRAY[i].interrupt();
    
56.     }
    
57.     Thread.sleep(100); // wait a moment for termination, to lazy for join ;)
    
58.   }
    
59. 
    
60.   public static void printResults() {
    
61.         System.out.println("lock creator = " + LOCK_CREATOR);
    
62.     for (int i = 0; i < RUNNABLE_ARRAY.length; i++) {
    
63.       System.out.println("runnable[" + i + "]: " + RUNNABLE_ARRAY[i]);
    
64.     }
    
65.   }
    
66. 
    
67.   public void run() {
    
68.         threadId = Thread.currentThread().getName();
    
69.         Object myLock = getLock();
    
70.     for (;;) {
    
71.       synchronized (myLock) {
    
72.         counter++;
    
73.         try {
    
74.           Thread.sleep(10);
    
75.         } catch (InterruptedException ex) {
    
76.           break;
    
77.         }
    
78.       }
    
79.     }
    
80.   }
    
81. 
    
82.   public String toString() {
    
83.     return "thread name = " + threadId + ", counter=" + counter;
    
84.   }
    
85. }

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key

需要注意的是，我这里运行出来的biased locking结果和原文作者那种极端的starving是不同的，
估计是jdk版本改进后的结果。

原帖由 key 于 30-8-2010 15:20 发表

                               
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之前一直没有注意到Biased Locking的存在。刚刚做了一下实验，的确如此。
下面是程序实验及相关的出处。不过我把程序小改了一下。

1. 参考文章出处：http://ceki.blogspot.com/2009/06/biased-locking-in-java-s ...