为什么使用两个线程作为计数器会降低Java的性能?

在里面 python 使用两个 Threads 对于一个简单的计数器程序(如下所示),它比使用单个计数器的程序慢 thread 。原因是背后的机制 Global Interpreter lock .

我在 java 看演出。在这里,我再次看到 Thread 表现出色 two-threaded 一个具有显著的时间尺度。为什么会这样?

代码如下:

public class ThreadTiming {

    static void threadMessage(String message) {
        String threadName =
            Thread.currentThread().getName();
        System.out.format("%s: %s%n",
                          threadName,
                          message);
    }

    private static class Counter implements Runnable {

        private int count=500000000;
        @Override
        public void run() {

            while(count>0) {
                count--;
            }
            threadMessage("done processing");
        }
    }

    public static void main(String[] args) throws InterruptedException{
        Thread t1 = new Thread(new Counter());
        Thread t2 = new Thread(new Counter());

        long startTime=System.currentTimeMillis();
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        long endTime=System.currentTimeMillis();
        System.out.println("Time taken by two threads "+ (endTime-startTime)/1000.0);

        startTime=System.currentTimeMillis();
        Calculate(2*500000000);
        endTime=System.currentTimeMillis();
        System.out.println("Time taken by single thread "+ (endTime-startTime)/1000.0);
    }

    public static void Calculate(int x){
        while (x>0){
            x--;
        }
        threadMessage("Done processing");
    }
}

输出:

Thread-1: done processing
Thread-2: done processing
Time taken by two threads 0.052
main: Done processing
Time taken by single thread 0.0010