参见：https://csp1999.blog.csdn.net/article/details/116903563 优先看这个
https://nyimac.gitee.io/2020/07/03/JVM%E5%AD%A6%E4%B9%A0/
https://blog.csdn.net/weixin_50280576/article/details/113784268
https://blog.csdn.net/m0_37989980/article/details/111193308 杂乱，如同看一本书，没有总结性的