打印Mark Work信息

    1. //引入工具包依赖
    2. <dependency>
    3.     <groupId>org.openjdk.jol</groupId>
    4.     <artifactId>jol-core</artifactId>
    5.     <version>0.8</version>
    6. </dependency>
    1. //示例代码
    3. @Slf4j
    4. public class MonitorDemo {
    6.     static Object monitor = new Object();
    8.     public static void main(String[] args) {
    9.         defaultLock();
    10. //        lock2();
    11.     }
    13.     public static void lock2(){
    14.         new Thread(() -> {
    15.             synchronized (monitor){
    16.                 try {
    17.                     print(monitor);
    18.                     Thread.sleep(5000);
    19.                 } catch (InterruptedException e) {
    20.                     e.printStackTrace();
    21.                 }
    22.             }
    23.         }).start();
    24.         try {
    25.             Thread.sleep(3000);
    26.         } catch (InterruptedException e) {
    27.             e.printStackTrace();
    28.         }
    29.         new Thread(() -> {
    30.             //存在锁竞争，锁膨胀至重量级锁
    31.             synchronized (monitor){
    32.                 print(monitor);
    33.             }
    34.         }).start();
    35.     }
    37.     /**
    38.      * VM参数：-XX:+UseBiasedLocking -XX:BiasedLockingStartupDelay=0
    39.      * 使JVM不延迟加载偏向锁，默认是延迟几秒的，因为JVM初始化期间存在大量的同步方法，锁升级会严重影响性能
    40.      */
    41.     public static void defaultLock(){
    42.         //打印初始的Mark Work
    43.         print(monitor);
    44.         synchronized (monitor){
    45.             //偏向锁
    46.             log.info("locking...");
    47.             print(monitor);
    48.         }
    49.         //锁释放
    50.         print(monitor);
    51.         new Thread(() -> {
    52.             //更新偏向锁获得者的线程ID
    53.             synchronized (monitor){
    54.                 log.info("locking 2 ...");
    55.                 print(monitor);
    56.             }
    57.         }).start();
    58.         // 计算hashcode，Mark Work中的线程ID位置被占用，偏向锁永久撤销
    59.         System.out.println(monitor.hashCode());
    60.         print(monitor);
    61.         //锁升级至轻量级锁
    62.         synchronized (monitor){
    63.             log.info("locking...");
    64.             print(monitor);
    65.         }
    66.     }
    68.     public static void print(Object monitor){
    69.         log.info("# # # # # # # # # # # # # # # # # # # # ");
    70.         log.info(ClassLayout.parseInstance(monitor).toPrintable());
    71.     }
    73. }

    Mark Work打印信息
    image.png