一、People

public class People {
    private Integer id;
    private String name;
    private Integer age;
    private String job;
    private String sex;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }
    public void print(){
        System.out.println("我是print本人");
    }
}

二、测试

    /**
     * 案例1：模拟线上环境OOM
     */
    @GetMapping("/add")
    public void addObject(){
        System.err.println("add"+peopleSevice);
        ArrayList<People> people = new ArrayList<>();
        while (true){
            people.add(new People());
        }
    }

三、参数设置

常用参数

-XX:+PrintGCDetails
-XX:MetaspaceSize=64m
-Xss512K
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=heap/heapdump3.hprof
-XX:SurvivorRatio=8
-XX:+PrintGCDateStamps
-Xms80M
-Xmx80M
-Xloggc:log/gc-oom3.log

1、设置内存

-Xms80M
-Xmx80M

2、输出GC打印

-XX:+PrintGCDetails

image.png
java.lang.OutOfMemoryError: Java heap space.png

2022-04-29T13:48:53.158-0800: [GC (Allocation Failure) [PSYoungGen: 5632K->609K(11264K)] 15448K->10426K(45568K), 0.0027678 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 
Disconnected from the target VM, address: '127.0.0.1:61538', transport: 'socket'
2022-04-29T13:49:29.950-0800: [GC (Allocation Failure) [PSYoungGen: 6241K->673K(11264K)] 16058K->10727K(45568K), 0.0201017 secs] [Times: user=0.01 sys=0.00, real=0.02 secs] 
2022-04-29 13:49:29.997  INFO 47978 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'
Heap
 PSYoungGen      total 11264K, used 1002K [0x00000007bef80000, 0x00000007c0000000, 0x00000007c0000000)
  eden space 5632K, 5% used [0x00000007bef80000,0x00000007befd20f0,0x00000007bf500000)
  from space 5632K, 11% used [0x00000007bfa80000,0x00000007bfb287c8,0x00000007c0000000)
  to   space 5632K, 0% used [0x00000007bf500000,0x00000007bf500000,0x00000007bfa80000)
 ParOldGen       total 34304K, used 10053K [0x00000007bce00000, 0x00000007bef80000, 0x00000007bef80000)
  object space 34304K, 29% used [0x00000007bce00000,0x00000007bd7d1598,0x00000007bef80000)
 Metaspace       used 34745K, capacity 36868K, committed 37424K, reserved 1081344K
  class space    used 4642K, capacity 5032K, committed 5168K, reserved 1048576K

Process finished with exit code 130 (interrupted by signal 2: SIGINT)

3、输出日志

-Xloggc:log/gc-oom3.log

4、生成Dump文件

-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=heap/heapdump3.hprof

四、GC日志分析

1、GCeasy分析工具

2、GCeasy结果分析

五、dump文件分析

方式1、MAT(Memory Analyzer Tool)

方式2、jvisualvm，可以通过终端来调起jvisualvm image.png