[Java知识库]jvm堆外内存泄漏分析简介

先上一个代码demo,利用unsafe开辟1g内存空间，不释放。

import java.lang.reflect.Field;
import java.util.concurrent.CountDownLatch;

import sun.misc.Unsafe;

public class OutOfHeapOOM {
    public static final Unsafe UNSAFE;
    static {
        try {
            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
            theUnsafe.setAccessible(true);
            UNSAFE = (Unsafe) theUnsafe.get(null);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    public static void main(String[] args) {
        CountDownLatch latch = new CountDownLatch(1);
        Thread thread = new Thread(() -> {
            UNSAFE.allocateMemory(1024 * 1024 * 1024);
            try {
                latch.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        thread.setName("oom thread");
        thread.start();
    }
}

javac?OutOfHeapOOM.java生成字节码文件

排查步骤：

java -XX:NativeMemoryTracking=detail OutOfHeapOOM

jcmd pid VM.native_memory detail scale=MB > temp.tx

根据下面的pmap命令输出的地址找到pid

strace -f -e trace=mmap java -XX:NativeMemoryTracking=detail OutOfHeapOOM

打印进程内存映射地址

pmap pid

查看线程栈快照

jstack pid