Java常见性能问题定位

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   /**
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     * 模拟CPU占满
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     */
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    @GetMapping("/cpu/loop")
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    public void testCPULoop() throws InterruptedException {
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        System.out.println("请求cpu死循环");
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        Thread.currentThread().setName("loop-thread-cpu");
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        int num = 0;
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        while (true) {
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            num++;
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            if (num == Integer.MAX_VALUE) {
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                System.out.println("reset");
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            }
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            num = 0;
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        }
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    }

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 ExecutorService service = new ThreadPoolExecutor(4, 10,
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            0, TimeUnit.SECONDS, new LinkedBlockingQueue(1024),
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            Executors.defaultThreadFactory(),
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            new ThreadPoolExecutor.AbortPolicy());
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   /**
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     * 模拟死锁
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     */
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    @GetMapping("/cpu/test")
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    public String testCPU() throws InterruptedException {
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        System.out.println("请求cpu");
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        Object lock1 = new Object();
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        Object lock2 = new Object();
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        service.submit(new DeadLockThread(lock1, lock2), "deadLookThread-" + new Random().nextInt());
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        service.submit(new DeadLockThread(lock2, lock1), "deadLookThread-" + new Random().nextInt());
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        return "ok";
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    }
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public class DeadLockThread implements Runnable {
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    private Object lock1;
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    private Object lock2;
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    public DeadLockThread1(Object lock1, Object lock2) {
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        this.lock1 = lock1;
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        this.lock2 = lock2;
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    }
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    @Override
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    public void run() {
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        synchronized (lock2) {
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            System.out.println(Thread.currentThread().getName()+"get lock2 and wait lock1");
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            try {
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                TimeUnit.MILLISECONDS.sleep(2000);
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            } catch (InterruptedException e) {
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                e.printStackTrace();
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            }
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            synchronized (lock1) {
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                System.out.println(Thread.currentThread().getName()+"get lock1 and lock2 ");
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            }
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        }
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    }
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}

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Java stack information for the threads listed above:
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===================================================
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"pool-1-thread-2":
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        at top.luozhou.analysisdemo.controller.DeadLockThread2.run(DeadLockThread.java:30)
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        - waiting to lock  (a java.lang.Object)
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        - locked  (a java.lang.Object)
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        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
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        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
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        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
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        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
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        at java.lang.Thread.run(Thread.java:748)
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"pool-1-thread-1":
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        at top.luozhou.analysisdemo.controller.DeadLockThread1.run(DeadLockThread.java:30)
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        - waiting to lock  (a java.lang.Object)
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        - locked  (a java.lang.Object)
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        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
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        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
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        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
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        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
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        at java.lang.Thread.run(Thread.java:748)
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 Found 5 deadlocks.

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 @GetMapping(value = "/thread/swap")
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    public String theadSwap(int num) {
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        System.out.println("模拟线程切换");
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        for (int i = 0; i 总结
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本文模拟了常见的性能问题场景，分析了如何定位CPU100%、内存泄漏、死锁、线程频繁切换问题。分析问题我们需要做好两件事，第一，掌握基本的原理，第二，借助好工具。本文也列举了分析问题的常用工具和命令，希望对你解决问题有所帮助。当然真正的线上环境可能十分复杂，并没有模拟的环境那么简单，但是原理是一样的，问题的表现也是类似的，我们重点抓住原理，活学活用，相信复杂的线上问题也可以顺利解决。
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参考
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1、https://linux.die.net/man/1/pidstat
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2、https://linux.die.net/man/8/vmstat
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3、https://help.eclipse.org/2020-03/index.jsp?topic=/org.eclipse.mat.ui.help/welcome.html
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4、https://www.linuxblogs.cn/articles/18120200.html
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5、https://www.tutorialspoint.com/what-is-context-switching-in-operating-system
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原文链接：https://snailclimb.gitee.io/javaguide/#/./docs/java/%E6%89%8B%E6%8A%8A%E6%89%8B%E6%95%99%E4%BD%A0%E5%AE%9A%E4%BD%8D%E5%B8%B8%E8%A7%81Java%E6%80%A7%E8%83%BD%E9%97%AE%E9%A2%98