新生代内存不足创建的对象直接进入老年代

package com.tech.gc.gc;

import java.util.ArrayList;
import java.util.List;


public class Demo_1 {
    private static final int _512KB = 512 * 1024;
    private static final int _1MB = 1024 * 1024;
    private static final int _6MB = 6 * 1024 * 1024;
    private static final int _7MB = 7 * 1024 * 1024;
    private static final int _8MB = 8 * 1024 * 1024;

    public static void main(String[] args) {
        List list = new ArrayList();
        list.add(new byte[_8MB]);
    }
}

设置JVM参数

堆的初始和最大内存为20M,新生代分配10M老年代剩余10M,使用SerialGC垃圾回收器，打印GC日志
-Xms20M -Xmx20M -Xmn10M -XX:+UseSerialGC -XX:+PrintGCDetails -verbose:gc

运行日志：

"C:Program FilesJavajdk1.8.0_251binjava.exe" -Xms20M -Xmx20M -Xmn10M -XX:+UseSerialGC -XX:+PrintGCDetails -verbose:gc "-javaagent:D:TechresourceIntelliJ IDEA 2018.3.1libidea_rt.jar=57058:D:TechresourceIntelliJ IDEA 2018.3.1bin" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_251jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_251jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_251jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_251jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_251jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_251jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_251jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_251jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_251jrelibextnashorn.jar;C:Program FilesJavajdk1.8.0_251jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_251jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_251jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_251jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_251jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_251jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_251jrelibjce.jar;C:Program FilesJavajdk1.8.0_251jrelibjfr.jar;C:Program FilesJavajdk1.8.0_251jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_251jrelibjsse.jar;C:Program FilesJavajdk1.8.0_251jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_251jrelibplugin.jar;C:Program FilesJavajdk1.8.0_251jrelibresources.jar;C:Program FilesJavajdk1.8.0_251jrelibrt.jar;D:Techcodetech-jvmtargetclasses;C:Userslw.m2repositoryorgprojectlomboklombok1.18.22lombok-1.18.22.jar;C:Userslw.m2repositorycomfasterxmljacksoncorejackson-annotations2.12.4jackson-annotations-2.12.4.jar;C:Userslw.m2repositorycomfasterxmljacksoncorejackson-core2.12.4jackson-core-2.12.4.jar;C:Userslw.m2repositorycomfasterxmljacksoncorejackson-databind2.12.4jackson-databind-2.12.4.jar" com.tech.gc.gc.Demo_1
Heap
 def new generation   total 9216K, used 2203K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)
  eden space 8192K,  26% used [0x00000000fec00000, 0x00000000fee26ec0, 0x00000000ff400000)
  from space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)
  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)
 tenured generation   total 10240K, used 8192K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)
   the space 10240K,  80% used [0x00000000ff600000, 0x00000000ffe00010, 0x00000000ffe00200, 0x0000000100000000)
 metaspace       used 3274K, capacity 4496K, committed 4864K, reserved 1056768K
  class space    used 357K, capacity 388K, committed 512K, reserved 1048576K

Process finished with exit code 0

新生代的Eden区、From区、To区分别为8M 1M 1M，有一部分系统对象占用了Eden区一部分内存，当添加一个8M数组时，新生代的Eden区和From区都放不下它，对象被直接放入到了老年代，并没有GC的产生。