jvm内存泄露和内存死锁排查

使用工具jconsole和visualvm

jconsole可以查看内存状况和死锁

内存泄露代码

package com.test;

import java.util.*;

public class Heap{

    public static void main(String[] args) throws InterruptedException{

        ArrayList list=new ArrayList();
        Integer count = 0;
        Thread.sleep(30000);

        System.out.print("start");
        while(true){
            //System.out.println("第次"+ ++count +"进入循环-----");
            Thread.sleep(50);
            list.add(new Heap());
        }

    }

}

死锁代码

package com.test;


public class SynAddRunable {

    static class synRun implements Runnable {
        int a;
        int b;

        public synRun(int a, int b) {
            this.a = a;
            this.b = b;
        }

        @Override
        public void run() {
            // Integer.valueOf(a) 会换存-128~127的数字，实际就返回了2和3两个对象
            synchronized (Integer.valueOf(a)) {
                // 假如在两个synchronized之间发生了线程切换，那就会出现线程a等待线程b的(Integer.valueOf(b))对象，
                // 而线程b又等待线程a的(Integer.valueOf(a))的对象，结果都跑不下去了，线程卡住，都等不了对方释放锁了
                synchronized (Integer.valueOf(b)) {
                    System.out.println(a + " + " + b + "=" + (a + b));
                }
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Thread.sleep(30000);// 30秒，有空余时间来启动,jconsole,并链接这个java进程
        System.out.println("start------");
        // 200个线程
        for (int i = 0; i < 100; i++) {
            new Thread(new synRun(2, 3)).start();
            new Thread(new synRun(3, 2)).start();
        }
        System.out.println("end------");
        Thread.sleep(10000000);// 一直停顿，方便查看数据

    }

}

 

线程等待代码

package com.test;

import java.io.*;

public class BusyThread {

    /**
     * 线程死循环演示
     */
    public static void createBusyThread() {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                while (true)   // 第41行
                    ;
            }
        }, "testBusyThread");
        thread.start();
    }

    /**
     * 线程锁等待演示
     */
    public static void createLockThread(final Object lock) {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (lock) {
                    try {
                        lock.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "testLockThread");
        thread.start();
    }

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        br.readLine();
        createBusyThread();
        br.readLine();
        Object obj = new Object();
        createLockThread(obj);
    }


}

 

visualvm查看堆dump排查内存泄露

 

 线程死锁

jconsole