高并发： High Concurrency

CPU 多级缓存： 数据 存取 通过高速缓存 cache。一级缓存 二级缓存 三级缓存

时间局部性  空间局部性

缓存一致性 MESI （修改  独享 共享 无效） 

乱序执行优化

 

 

JAVA虚拟机-内存模型 JMM

堆： 用户对象信息存储

栈： 对象引用、基本类型变量存储，堆区对象的私有拷贝

 

 

import com.imooc.concurrency.annoations.NodThreadSafe;import java.util.concurrent.CountDownLatch;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Semaphore;@NodThreadSafepublic class ConcurrentyTest {    // 请求总数    public static int countTotle = 5000;    // 并发执行线程数    public static int threadTotle = 200;    public static int sum = 0;    public static void main(String[] args)throws Exception {        ExecutorService executorService = Executors.newCachedThreadPool(); //线程池        final Semaphore semaphore = new Semaphore(threadTotle);             //信号量        final CountDownLatch countDownLatch = new CountDownLatch(countTotle); // 计数器        for (int i=0;i
     
      {                try {                    semaphore.acquire(); // 是否允许被执行                    add();                    semaphore.release();                } catch (Exception e) {                    e.printStackTrace();                }                countDownLatch.countDown();//计数器 -1            });        }        countDownLatch.await();        executorService.shutdown();        System.out.println(sum);    }    private static void add() {        sum++;    }}