Serviceability Agent (SA)是啥？
HotSpot Glossary of Terms 写道
The Serviceablity Agent is collection of Sun internal code that aids in debugging HotSpot problems. It is also used by several JDK tools - jstack, jmap, jinfo, and jdb. See SA for more information.
简单说，这部分是用来调试查看hotspot的。
Problem:1.VisualVM无法运行提示"Cannot find Java 1.7 or higher"
解决办法：
①.在VisualVM安装位置下找到etc目录
②.修改etc目录下的visualvm.conf文件
③.加入配置参数指定JDK或JRE路径，如 visualvm_jdkhome="D:\jdk1.7.0_07"
2.visualVM里面添加JConsole plugin插件
https://visualvm.java.net/jconsole_plugin_wrapper_tab.html
注意：jdk1.7中不一定有JTop.jar，可以从jdk1.6中拷贝过来
