Java JVM内存管理

java对象内存分配验证

对象在Eden区分配内存

/**
 * 对象优先在eden区域分配
 * -verbose:gc：在控制台输出gc情况
 * -Xms20M -Xmx20M：设置堆的大小
 * -Xmn10M：设置新生代大小10M
 * -XX:+PrintGCDetails“：打印GC详细信息
 * -XX:SurvivorRatio=8：定义了新生代中Eden区域和Survivor区域（From幸存区或To幸存区）的比例
 *
 * 启动参数: -verbose:gc -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:SurvivorRatio=8
 *
 */
public class EdenAllocateTest {

    //这边定义一个1MB的对象
    private static final int _1MB = 1024 * 1024;

    public static void main(String[] args) {
        //512K
        byte[] arr1 = new byte[_1MB / 2];
        System.out.println("1-----------------");
    }
}


/**===================================运行结果===================================*/

1-----------------
Heap
//新生区
 PSYoungGen      total 9216K, used 2692K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)
  //Eden 被使用32%
  eden space 8192K, 32% used [0x00000000ff600000,0x00000000ff8a1188,0x00000000ffe00000)
  from space 1024K, 0% used [0x00000000fff00000,0x00000000fff00000,0x0000000100000000)
  to   space 1024K, 0% used [0x00000000ffe00000,0x00000000ffe00000,0x00000000fff00000)
 ParOldGen       total 10240K, used 0K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)
  object space 10240K, 0% used [0x00000000fec00000,0x00000000fec00000,0x00000000ff600000)
 Metaspace       used 3340K, capacity 4496K, committed 4864K, reserved 1056768K
  class space    used 364K, capacity 388K, committed 512K, reserved 1048576K

验证大的对象直接进入老年代

/**
 * 验证大对象直接进入老年代
 * -XX:+UseSerialGC：新生代和老年代使用串行回收器
 * -XX:PretenureSizeThreshold=5M：大于5M这个值的参数直接在老年代分配。
 *
 * 启动参数: -XX:+UseSerialGC -verbose:gc -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:PretenureSizeThreshold=5M
 *
 * 只对Serial与ParNew垃圾收集器有效
 */

public class LargeObjectAllocate {

    private static final int _1MB = 1024 * 1024;

    public static void main(String[] args) {
        System.out.println(String.format("Allocate 【%dMB】, 【%dKB】 space", 6, 6 * 1024));
        //定义6MB对象，直接在老年代中分配内存
        byte[] bytes = new byte[6 * _1MB];
        System.out.println(String.format("End allocate 【%dMB】, 【%dKB】 space", 6, 6 * 1024));

    }
}

/**===================================运行结果===================================*/

Allocate 【6MB】, 【6144KB】 space
End allocate 【6MB】, 【6144KB】 space
Heap
 def new generation   total 9216K, used 3037K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)
  eden space 8192K,  37% used [0x00000000fec00000, 0x00000000feef7538, 0x00000000ff400000)
  from space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)
  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)
//老年代被使用6144K，差不多6MB的样子
 tenured generation   total 10240K, used 6144K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)
   the space 10240K,  60% used [0x00000000ff600000, 0x00000000ffc00010, 0x00000000ffc00200, 0x0000000100000000)
 Metaspace       used 3917K, capacity 4642K, committed 4864K, reserved 1056768K
  class space    used 435K, capacity 462K, committed 512K, reserved 1048576K

验证元空间OOM溢出

/**
 * 验证元空间溢出
 *
 * -XX:MetaspaceSize=10m -XX:MaxMetaspaceSize=10m：设置元空间大小
 * 启动参数: -XX:MetaspaceSize=10m -XX:MaxMetaspaceSize=10m
 *
 */


public class MetaspaceOOM {

    public static void main(String[] args) {
        //获取当前JVM的类加载信息
        ClassLoadingMXBean loadingMXBean = ManagementFactory.getClassLoadingMXBean();
        while(true) {
            //Enhancer是cglib中使用频率很高的一个类，它是一个字节码增强器，可以用来为无接口的类创建代理
            Enhancer enhancer = new Enhancer();
            enhancer.setSuperclass(MetaspaceOOM.class);
            enhancer.setCallbackTypes(new Class[]{Dispatcher.class, MethodInterceptor.class});
            enhancer.setCallbackFilter(new CallbackFilter() {

                @Override
                public int accept(Method method) {
                    return 1;
                }

                @Override
                public boolean equals(Object obj) {
                    return super.equals(obj);
                }
            });

            Class clazz = enhancer.createClass();
            System.out.println(clazz.getName());
            //显示数量信息（共加载过的类型数目，当前还有效的类型数目，已经被卸载的类型数目）
            System.out.println("total: " + loadingMXBean.getTotalLoadedClassCount());
            System.out.println("active: " + loadingMXBean.getLoadedClassCount());
            System.out.println("unloaded: " + loadingMXBean.getUnloadedClassCount());
        }

    }
}

/**===================================运行结果===================================*/

allocate.MetaspaceOOM$$EnhancerByCGLIB$$4837d5cd
total: 1204
active: 1204
unloaded: 0
Exception in thread "main" net.sf.cglib.core.CodeGenerationException: java.lang.reflect.InvocationTargetException-->null
  at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:237)
  at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
  at net.sf.cglib.proxy.Enhancer.createClass(Enhancer.java:317)
  at allocate.MetaspaceOOM.main(MetaspaceOOM.java:44)
Caused by: java.lang.reflect.InvocationTargetException
  at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:498)
  at net.sf.cglib.core.ReflectUtils.defineClass(ReflectUtils.java:384)
  at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:219)
  ... 3 more
    //元空间溢出
Caused by: java.lang.OutOfMemoryError: Metaspace
  at java.lang.ClassLoader.defineClass1(Native Method)
  at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
  ... 8 more

栈溢出验证

public class StackOverflowTest {

    private static int deep = 0;

    public static void main(String[] args) {
        try {
            recursive();
        } catch (Throwable t) {
            t.printStackTrace();
        }
        System.out.println("执行了：" + deep + "次");
    }

    //不断递归调用
    private static void recursive(){
        deep++;
        recursive();
    }
}

/**===================================运行结果===================================*/

...前省略
    //显示栈溢出
    at allocate.StackOverflowTest.recursive(StackOverflowTest.java:19)
  at allocate.StackOverflowTest.recursive(StackOverflowTest.java:19)
  at allocate.StackOverflowTest.recursive(StackOverflowTest.java:19)
  at allocate.StackOverflowTest.recursive(StackOverflowTest.java:19)
    //总共递归调用了26269次
执行了：26269次

堆溢出验证

/**
 * -Xmx10m -Xms10m
 */

public class StringOOMTest {
    public static void main(String[] args) {
        try {
            List<String> list = new ArrayList<>();
            for(int i = 0;; i++) {
                System.out.println(i);
                //JDK1.7常量池迁移到堆中，这里我们不断地在常量池中创建引用
                //这里的intern方法可以去多了解一下
                list.add(("String" + i++).intern());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

/**===================================运行结果===================================*/
...前省略
213420
    //堆空间溢出
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
  at java.util.Arrays.copyOf(Arrays.java:3210)
  at java.util.Arrays.copyOf(Arrays.java:3181)
  at java.util.ArrayList.grow(ArrayList.java:265)
  at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:239)
  at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:231)
  at java.util.ArrayList.add(ArrayList.java:462)
  at allocate.StringOOMTest.main(StringOOMTest.java:17)

验证长期存在的对象进入老年代

/**
 * 长期存活的对象进入老年代
 *
 * XX:MaxTenuringThreshold=3：设置年龄阈值，对象在Eden出生如果经第一次Minor GC后仍然存活, 且能被Survivor容纳的话, 将被移动到Survivor空间中, 并将年龄设为1. 以后对象在Survivor区中每熬过一次Minor GC年龄就+1. 当增加到设置的阀值时将会晋升到老年代。
 * -XX:+PrintTenuringDistribution：JVM 在每次新生代GC时，打印出幸存区中对象的年龄分布。
 * -XX:+PrintHeapAtGC：输出程序运行前后对的概况
 * 启动参数: -verbose:gc -Xms40M -Xmx40M -Xmn20M -XX:+PrintGCDetails -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=3 -XX:+PrintTenuringDistribution -XX:+UseSerialGC -XX:+PrintHeapAtGC
 */

public class TenuringTest {

    public static void main(String[] args) throws Exception {
        
        byte[] arr1 = AllocateUtil.allocate256KB();
        AllocateUtil.allocate8MB();
        System.out.println("\n");

        System.in.read();
        System.out.println("1111=========");
        AllocateUtil.allocate8MB();
        byte[] arr2 = AllocateUtil.allocate512KB();
        System.out.println("\n");

        System.in.read();
        System.out.println("22222=============");
        AllocateUtil.allocate8MB();
        byte[] arr3 = AllocateUtil.allocate256KB();
        System.out.println("\n");

        System.in.read();
        System.out.println("3333=============");
        AllocateUtil.allocate8MB();
        byte[] arr4 = AllocateUtil.allocate512KB();
        System.out.println("\n");

        System.in.read();
        System.out.println("4444=============");
        AllocateUtil.allocate8MB();
        byte[] arr5 = AllocateUtil.allocate256KB();
        System.out.println("\n");

        System.in.read();
        System.out.println("55555=============");
        AllocateUtil.allocate8MB();
        byte[] arr6 = AllocateUtil.allocate512KB();
        System.out.println("\n");

        System.in.read();
        System.out.println("6666=============");
        AllocateUtil.allocateMB(8);
    }

}
class AllocateUtil {

    private static final int _1KB = 1024;

    private static final int _1MB = _1KB * 1024;

    public static byte[] allocate8MB() {
        return allocateMB(8);
    }

    public static byte[] allocateMB(int mb) {
        System.out.println(String.format("Allocate 【%dMB】, 【%dKB】 space", mb, mb * 1024));
        byte[] bytes = new byte[mb * _1MB];
        System.out.println(String.format("End allocate 【%dMB】, 【%dKB】 space", mb, mb * 1024));
        return bytes;
    }

    public static byte[] allocateKB(int kb) {
        System.out.println(String.format("Allocate 【%dKB】 space", kb));
        return new byte[kb * _1KB];
    }


    public static byte[] allocate256KB() {
        return allocateKB(256);
    }

    public static byte[] allocate512KB() {
        return allocateKB(512);
    }
}

/**===================================运行结果===================================*/

Allocate 【256KB】 space
Allocate 【8MB】, 【8192KB】 space
End allocate 【8MB】, 【8192KB】 space

1111=========
Allocate 【8MB】, 【8192KB】 space
{Heap before GC invocations=0 (full 0):
 def new generation   total 18432K, used 12409K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  //创建对象在Eden区
  eden space 16384K,  75% used [0x00000000fd800000, 0x00000000fe41e698, 0x00000000fe800000)
  from space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
 tenured generation   total 20480K, used 0K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   0% used [0x00000000fec00000, 0x00000000fec00000, 0x00000000fec00200, 0x0000000100000000)
 Metaspace       used 3779K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [DefNew
Desired survivor size 1048576 bytes, new threshold 1 (max 3)
  //1130720 / 1024 = 1028K岁数为1
- age   1:    1130720 bytes,    1130720 total
: 12409K->1104K(18432K), 0.0013928 secs] 12409K->1104K(38912K), 0.0014149 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap after GC invocations=1 (full 0):
 def new generation   total 18432K, used 1104K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,   0% used [0x00000000fd800000, 0x00000000fd800000, 0x00000000fe800000)
  from space 2048K,  53% used [0x00000000fea00000, 0x00000000feb140e0, 0x00000000fec00000)
  to   space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
 tenured generation   total 20480K, used 0K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   0% used [0x00000000fec00000, 0x00000000fec00000, 0x00000000fec00200, 0x0000000100000000)
 Metaspace       used 3779K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
}
End allocate 【8MB】, 【8192KB】 space
Allocate 【512KB】 space

22222=============
Allocate 【8MB】, 【8192KB】 space
{Heap before GC invocations=1 (full 0):
 def new generation   total 18432K, used 10450K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,  57% used [0x00000000fd800000, 0x00000000fe120960, 0x00000000fe800000)
  from space 2048K,  53% used [0x00000000fea00000, 0x00000000feb140e0, 0x00000000fec00000)
  to   space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
 tenured generation   total 20480K, used 0K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   0% used [0x00000000fec00000, 0x00000000fec00000, 0x00000000fec00200, 0x0000000100000000)
 Metaspace       used 3779K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [DefNew
Desired survivor size 1048576 bytes, new threshold 3 (max 3)
  //524384 / 1024 = 512岁数为1
- age   1:     524384 bytes,     524384 total
: 10450K->512K(18432K), 0.0012789 secs] 10450K->1540K(38912K), 0.0012954 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap after GC invocations=2 (full 0):
 def new generation   total 18432K, used 512K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,   0% used [0x00000000fd800000, 0x00000000fd800000, 0x00000000fe800000)
  from space 2048K,  25% used [0x00000000fe800000, 0x00000000fe880060, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
  //之前的对象以及进入老年代了                        
 tenured generation   total 20480K, used 1028K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   5% used [0x00000000fec00000, 0x00000000fed01110, 0x00000000fed01200, 0x0000000100000000)
 Metaspace       used 3779K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
}
End allocate 【8MB】, 【8192KB】 space
Allocate 【256KB】 space

3333=============
Allocate 【8MB】, 【8192KB】 space
{Heap before GC invocations=2 (full 0):
 def new generation   total 18432K, used 9016K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,  51% used [0x00000000fd800000, 0x00000000fe04e2e8, 0x00000000fe800000)
  from space 2048K,  25% used [0x00000000fe800000, 0x00000000fe880060, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
 tenured generation   total 20480K, used 1028K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   5% used [0x00000000fec00000, 0x00000000fed01110, 0x00000000fed01200, 0x0000000100000000)
 Metaspace       used 3780K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [DefNew
Desired survivor size 1048576 bytes, new threshold 3 (max 3)
 //524384 / 1024 = 512岁数为2
 //262240 / 1024 = 256岁数为1                         
- age   1:     262240 bytes,     262240 total
- age   2:     524384 bytes,     786624 total
: 9016K->768K(18432K), 0.0016583 secs] 10045K->1796K(38912K), 0.0016733 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap after GC invocations=3 (full 0):
 def new generation   total 18432K, used 768K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,   0% used [0x00000000fd800000, 0x00000000fd800000, 0x00000000fe800000)
  from space 2048K,  37% used [0x00000000fea00000, 0x00000000feac00c0, 0x00000000fec00000)
  to   space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
 tenured generation   total 20480K, used 1028K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   5% used [0x00000000fec00000, 0x00000000fed01110, 0x00000000fed01200, 0x0000000100000000)
 Metaspace       used 3780K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
}
End allocate 【8MB】, 【8192KB】 space
Allocate 【512KB】 space

4444=============
Allocate 【8MB】, 【8192KB】 space
{Heap before GC invocations=3 (full 0):
 def new generation   total 18432K, used 9786K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,  55% used [0x00000000fd800000, 0x00000000fe0ce760, 0x00000000fe800000)
  from space 2048K,  37% used [0x00000000fea00000, 0x00000000feac00c0, 0x00000000fec00000)
  to   space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
 tenured generation   total 20480K, used 1028K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   5% used [0x00000000fec00000, 0x00000000fed01110, 0x00000000fed01200, 0x0000000100000000)
 Metaspace       used 3781K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [DefNew
Desired survivor size 1048576 bytes, new threshold 3 (max 3)
 //524384 / 1024 = 512岁数为3
 //262240 / 1024 = 256岁数为2
 //524384 / 1024 = 512岁数为1
- age   1:     524384 bytes,     524384 total
- age   2:     262240 bytes,     786624 total
- age   3:     524384 bytes,    1311008 total
: 9786K->1280K(18432K), 0.0005653 secs] 10814K->2308K(38912K), 0.0005804 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap after GC invocations=4 (full 0):
 def new generation   total 18432K, used 1280K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,   0% used [0x00000000fd800000, 0x00000000fd800000, 0x00000000fe800000)
  from space 2048K,  62% used [0x00000000fe800000, 0x00000000fe940120, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
 tenured generation   total 20480K, used 1028K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   5% used [0x00000000fec00000, 0x00000000fed01110, 0x00000000fed01200, 0x0000000100000000)
 Metaspace       used 3781K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
}
End allocate 【8MB】, 【8192KB】 space
Allocate 【256KB】 space

55555=============
Allocate 【8MB】, 【8192KB】 space
{Heap before GC invocations=4 (full 0):
 def new generation   total 18432K, used 9790K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,  51% used [0x00000000fd800000, 0x00000000fe04f818, 0x00000000fe800000)
  from space 2048K,  62% used [0x00000000fe800000, 0x00000000fe940120, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
 tenured generation   total 20480K, used 1028K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   5% used [0x00000000fec00000, 0x00000000fed01110, 0x00000000fed01200, 0x0000000100000000)
 Metaspace       used 3781K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [DefNew
Desired survivor size 1048576 bytes, new threshold 3 (max 3)
  //同上
- age   1:     262240 bytes,     262240 total
- age   2:     524384 bytes,     786624 total
- age   3:     262240 bytes,    1048864 total
: 9790K->1024K(18432K), 0.0008305 secs] 10818K->2564K(38912K), 0.0008514 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap after GC invocations=5 (full 0):
 def new generation   total 18432K, used 1024K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,   0% used [0x00000000fd800000, 0x00000000fd800000, 0x00000000fe800000)
  from space 2048K,  50% used [0x00000000fea00000, 0x00000000feb00120, 0x00000000fec00000)
  to   space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
 tenured generation   total 20480K, used 1540K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   7% used [0x00000000fec00000, 0x00000000fed81170, 0x00000000fed81200, 0x0000000100000000)
 Metaspace       used 3781K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
}
End allocate 【8MB】, 【8192KB】 space
Allocate 【512KB】 space

6666=============
Allocate 【8MB】, 【8192KB】 space
{Heap before GC invocations=5 (full 0):
 def new generation   total 18432K, used 10045K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,  55% used [0x00000000fd800000, 0x00000000fe0cf4e0, 0x00000000fe800000)
  from space 2048K,  50% used [0x00000000fea00000, 0x00000000feb00120, 0x00000000fec00000)
  to   space 2048K,   0% used [0x00000000fe800000, 0x00000000fe800000, 0x00000000fea00000)
 tenured generation   total 20480K, used 1540K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   7% used [0x00000000fec00000, 0x00000000fed81170, 0x00000000fed81200, 0x0000000100000000)
 Metaspace       used 3782K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
[GC (Allocation Failure) [DefNew
Desired survivor size 1048576 bytes, new threshold 3 (max 3)
- age   1:     524384 bytes,     524384 total
- age   2:     262240 bytes,     786624 total
- age   3:     524384 bytes,    1311008 total
: 10045K->1280K(18432K), 0.0004927 secs] 11585K->3076K(38912K), 0.0005076 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap after GC invocations=6 (full 0):
 def new generation   total 18432K, used 1280K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,   0% used [0x00000000fd800000, 0x00000000fd800000, 0x00000000fe800000)
  from space 2048K,  62% used [0x00000000fe800000, 0x00000000fe940120, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
 tenured generation   total 20480K, used 1796K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   8% used [0x00000000fec00000, 0x00000000fedc11d0, 0x00000000fedc1200, 0x0000000100000000)
 Metaspace       used 3782K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 411K, capacity 434K, committed 512K, reserved 1048576K
}
End allocate 【8MB】, 【8192KB】 space
Heap
 def new generation   total 18432K, used 10120K [0x00000000fd800000, 0x00000000fec00000, 0x00000000fec00000)
  eden space 16384K,  53% used [0x00000000fd800000, 0x00000000fe0a20e0, 0x00000000fe800000)
  from space 2048K,  62% used [0x00000000fe800000, 0x00000000fe940120, 0x00000000fea00000)
  to   space 2048K,   0% used [0x00000000fea00000, 0x00000000fea00000, 0x00000000fec00000)
 tenured generation   total 20480K, used 1796K [0x00000000fec00000, 0x0000000100000000, 0x0000000100000000)
   the space 20480K,   8% used [0x00000000fec00000, 0x00000000fedc11d0, 0x00000000fedc1200, 0x0000000100000000)
 Metaspace       used 3788K, capacity 4670K, committed 4864K, reserved 1056768K
  class space    used 412K, capacity 434K, committed 512K, reserved 1048576K
Disconnected from the target VM, address: '127.0.0.1:50446', transport: 'socket'

Process finished with exit code 0