Java 9 中 Thread.onSpinWait() 方法的重要性?


Thread.onSpinWait() 方法已在 Java 9 中引入。它是 Thread 类的静态方法,可以在忙等待循环中按需调用。在某些系统架构上,它允许 JVM 发出处理器指令以改善此类自旋等待循环的反应时间,同时降低核心线程的耗电量。它可以使 Java 程序的整体功耗受益,并允许其他核心线程在相同的功耗范围内以更快的速度执行。

语法

public static void onSpinWait()

示例

public class ThreadOnSpinWaitTest {
   public static void main(final String args[]) throws InterruptedException {
      final NormalTask task1 = new NormalTask();
      final SpinWaitTask task2 = new SpinWaitTask();
      final Thread thread1 = new Thread(task1);
      thread1.start();
      final Thread thread2 = new Thread(task2);
      thread2.start();
      new Thread(() -> {
         try {
            Thread.sleep(1000);
         } catch(final InterruptedException e) {
            e.printStackTrace();
         } finally {
            task1.start();
            task2.sta*rt();
         }
      }).start();
      thread1.join();
      thread2.join();
   }
   private abstract static class Task implements Runnable {
      volatile boolean canStart;
      void start() {
         this.canStart = true;
      }
   }
   private static class NormalTask extends Task {
      @Override
      public void run() {
         while(!this.canStart) {
         }
         System.out.println("Done!");
      }
   }
   private static class SpinWaitTask extends Task {
      @Override
      public void run() {
         while(!this.canStart) {
            Thread.onSpinWait();
         }
         System.out.println("Done!");
      }
   }
}

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输出

Done!
Done!

更新于: 31-3-2020

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