JVM学习笔记-内存溢出
JVM学习笔记-内存处理一文中已经介绍了JVM对内存区域的划分和处理。在实际编程过程中,会遇到一些OutOfMemory(OOM)异常。通过模拟。我们可以直接指出这些场景的本质,从而在纷繁复杂的千万行代码中避免这样去Coding。导致OOM的情况有多种,包括Java或Native Method Stack的内存不足或者栈空间溢出、Heap内存溢出、Non-heap内存溢出、Direct Memory溢出。
Java Method Stack栈溢出模拟
什么时候会让Java Method Stack栈溢出?栈的基本特点就是FILO(First In Last Out),如果in的太多而out的太少,就可能overflow了。而Java Method Statck的功能就是保存每一次函数调用时的“现场”,即为入栈,函数返回对应出栈,所以函数的调用深度越大,栈就变得越大,足够大的时候就会溢出。所以模拟Java Method Stack溢出,只要不断递归调用某一函数就可以导致溢出。
[java]
package com.jony.java;
public class TestStackOverflow {
private int stackLength = 0;
public void stackOverFlow(){
++stackLength;
stackOverFlow();
}
public static void main(String[] args){
TestStackOverflow test = new TestStackOverflow();
try {
test.stackOverFlow();
} catch (Throwable e) {
System.out.println("Stack Length:" + test.stackLength);
e.printStackTrace();
}
}
}
package com.jony.java;
public class TestStackOverflow {
private int stackLength = 0;
public void stackOverFlow(){
++stackLength;
stackOverFlow();
}
public static void main(String[] args){
TestStackOverflow test = new TestStackOverflow();
try {
test.stackOverFlow();
} catch (Throwable e) {
System.out.println("Stack Length:" + test.stackLength);
e.printStackTrace();
}
}
}
运行结果:
Stack Length:11477
java.lang.StackOverflowError
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:7)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
at com.jony.java.TestStackOverflow.stackOverFlow(TestStackOverflow.java:8)
2. Java Method Stack内存溢出模拟-Heap内存溢出
堆是用来存储对象的,当然对象不一定都存在堆里(栈上分配、标量替换技术)。那么堆如果溢出了,一定是不能被杀掉的对象太多了。模拟Heap内存溢出,只要不断的创建对象并保存对象引用存在即可。
[java]
package com.jony.java;
import java.util.ArrayList;
public class TestHeapOverflow {
static class TestOomHeap {}
public static void main(String[] args) {
ArrayList<TestOomHeap> list = new ArrayList<TestHeapOverflow.TestOomHeap>();
while (true) {
list.add(new TestOomHeap());
}
}
}
package com.jony.java;
import java.util.ArrayList;
public class TestHeapOverflow {
static class TestOomHeap {}
public static void main(String[] args) {
ArrayList<TestOomHeap> list = new ArrayList<TestHeapOverflow.TestOomHeap>();
while (true) {
list.add(new TestOomHeap());
}
}
}
运行结果:
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at com.jony.java.TestHeapOverflow.main(TestHeapOverflow.java:13)
3. Method Area内存溢出
Method Area内存溢出,也就是Non-heap,是用来存储Object Class Data、变量、静态常量、JIT编译后的代码。如果该区域溢出,则说明某种数据创建的实在是太多了,模拟该异常,可以不断创建新的class,知道溢出为止。下面实例中会用到asm-all-3.0.jar和cglib2.2.jar 下载
[java]
package com.jony.java;
import java.lang.reflect.Method;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
public class TestMethodAreaOverflow {
static class MethodAreaOom {}
public static void main(String[] args) {
while (true) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(MethodAreaOom.class);
enhancer.setUseCache(false);
enhancer.setCallback(new MethodInterceptor() {
@Override
public Object intercept(Object arg0, Method arg1, Object[] arg2,
MethodProxy proxy) throws Throwable {
return proxy.invoke(arg0, arg2);
}
});
补充:软件开发 , Java ,