参考：
JVM内存分区及作用（JDK8）
https://blog.csdn.net/BigBug_500/article/details/104734957
java 进程占用系统内存过高分析
https://blog.csdn.net/fxh13579/article/details/104754340
Java之jvm和线程的内存
https://blog.csdn.net/qq_39507276/article/details/123376949
JVM:浅谈CodeCache
https://www.jianshu.com/p/cbab2371b164
JVM参数与内存模型
https://www.cnblogs.com/lowerma/p/12404423.html
怎么做JDK8的内存调优
https://www.cnblogs.com/heihaozi/p/13417591.html
JVM内存分配(JDK8)
https://blog.csdn.net/paopaodog/article/details/127151177
top命令详解
https://blog.csdn.net/yaomingyang/article/details/78968573
JVM内存泄漏之MaxDirectMemory
https://www.jianshu.com/p/dfc847086ee1
Linux与JVM的内存关系分析
https://blog.csdn.net/William0318/article/details/124973838
JVM内存 ≈ Java永久代 ＋ Java堆(新生代和老年代) ＋ 线程栈＋ Java NIO
JVM堆内存详解
https://blog.csdn.net/guorui_java/article/details/109437377
