OutOfMemoryErrorLab

Java堆溢出

jvm参数设置：指定堆的大小，避免堆太大运行时间过长（运行的时间同样很长，不懂原因）测试堆内存溢出，没必要分配太大堆内存。-XX:+HeapDumpOnOutOfMemoryError开启HeapDumpOnOutOfMemoryError

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-Xmx51m -Xms24m -XX:+HeapDumpOnOutOfMemoryError

heapOOM.java

new对象存储在堆区，无限new对象可使堆内存溢出，new的对象存放List内避免对象被清理。

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public class HeapOOM {
    static class OOMObject{}
    public static void main(String[] args) {
        List<OOMObject> list = new ArrayList<>();
        while (true) list.add(new OOMObject());
    }
}

运行结果：

虚拟机栈和本地方法栈溢出

  1. 如果线程请求的栈深度大于虚拟机所允许的最大深度，将抛出StackOverflowError异常。
  2. 如果虚拟机的栈内存允许动态扩展，当扩展栈容量无法申请到足够的内存时，将抛出OutOfMemoryError异常。

1 栈深度过深

使用-Xss参数减少栈内存容量

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-Xss1m

class

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public class JavaVMStackSOF {

    private int stackLength = 0;
    private void stackLeak() {
        ++stackLength;
        stackLeak();
    }
    public static void main(String[] args) {
        JavaVMStackSOF oom = new JavaVMStackSOF();
        try{
            oom.stackLeak();
        } catch (StackOverflowError error) {
            System.out.println("oom.stackLength = " + oom.stackLength);
            throw error;
        }
    }
}

运行结果

image-20220424213613321

2 栈申请内存不足

栈大小参数

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-Xss128k

class

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public class JavaVMStackSOF2 {

    private static int stackLength = 0;

    public static void test() {
        long unused1, unused2, unused3, unused4, unused5,
                unused6, unused7, unused8, unused9, unused10,
                unused11, unused12, unused13, unused14, unused15,
                unused16, unused17, unused18, unused19, unused20,
                unused21, unused22, unused23, unused24, unused25,
                unused26, unused27, unused28, unused29, unused30,
                unused31, unused32, unused33, unused34, unused35,
                unused36, unused37, unused38, unused39, unused40,
                unused41, unused42, unused43, unused44, unused45,
                unused46, unused47, unused48, unused49, unused50,
                unused51, unused52, unused53, unused54, unused55,
                unused56, unused57, unused58, unused59, unused60,
                unused61, unused62, unused63, unused64, unused65,
                unused66, unused67, unused68, unused69, unused70,
                unused71, unused72, unused73, unused74, unused75,
                unused76, unused77, unused78, unused79, unused80,
                unused81, unused82, unused83, unused84, unused85,
                unused86, unused87, unused88, unused89, unused90,
                unused91, unused92, unused93, unused94, unused95,
                unused96, unused97, unused98, unused99, unused100;
        stackLength++;
        test();
        unused1 = unused2 = unused3 = unused4 = unused5 = unused6 =
            unused7 = unused8 = unused9 = unused10 =
            unused11 = unused12 = unused13 = unused14 = unused15 =
            unused16 = unused17 = unused18 = unused19 = unused20 =
            unused21 = unused22 = unused23 = unused24 = unused25 =
            unused26 = unused27 = unused28 = unused29 = unused30 =
            unused31 = unused32 = unused33 = unused34 = unused35 =
            unused36 = unused37 = unused38 = unused39 = unused40 =
            unused41 = unused42 = unused43 = unused44 = unused45 =
            unused46 = unused47 = unused48 = unused49 = unused50 =
            unused51 = unused52 = unused53 = unused54 = unused55 =
            unused56 = unused57 = unused58 = unused59 = unused60 =
            unused61 = unused62 = unused63 = unused64 = unused65 =
            unused66 = unused67 = unused68 = unused69 = unused70 =
            unused71 = unused72 = unused73 = unused74 = unused75 =
            unused76 = unused77 = unused78 = unused79 = unused80 =
            unused81 = unused82 = unused83 = unused84 = unused85 =
            unused86 = unused87 = unused88 = unused89 = unused90 =
            unused91 = unused92 = unused93 = unused94 = unused95 =
            unused96 = unused97 = unused98 = unused99 = unused100 = 0;
    }

    public static void main(String[] args) {
        try {
            test();
        } catch (Error e) {
            System.out.println("stackLength = " + stackLength);
            throw e;
        }
    }
}
jvm3

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