1、简介
JSTAT即JVM Statistics Monitoring Tool，JVM统计数据监控工具，可以用来查看JVM中GC、类加载等信息
- [option] : 操作参数
- LVMID : 本地虚拟机进程ID
- [interval] : 连续输出的时间间隔
- [count] : 连续输出的次数（默认一直打印）
参数解析：
| Option | Displays… |
|---|---|
| class | class loader的行为统计。Statistics on the behavior of the class loader. |
| compiler | HotSpt JIT编译器行为统计。Statistics of the behavior of the HotSpot Just-in-Time compiler. |
| gc | 垃圾回收堆的行为统计。Statistics of the behavior of the garbage collected heap. |
| gccapacity | 各个垃圾回收代容量(young,old,perm)和他们相应的空间统计。Statistics of the capacities of the generations and their corresponding spaces. |
| gcutil | 垃圾回收统计概述。Summary of garbage collection statistics. |
| gccause | 垃圾收集统计概述（同-gcutil），附加最近两次垃圾回收事件的原因。Summary of garbage collection statistics (same as -gcutil), with the cause of the last and |
| gcnew | 新生代行为统计。Statistics of the behavior of the new generation. |
| gcnewcapacity | 新生代与其相应的内存空间的统计。Statistics of the sizes of the new generations and its corresponding spaces. |
| gcold | 年老代和永生代行为统计。Statistics of the behavior of the old and permanent generations. |
| gcoldcapacity | 年老代行为统计。Statistics of the sizes of the old generation. |
| gcpermcapacity | 永生代行为统计。Statistics of the sizes of the permanent generation. |
| printcompilation | HotSpot编译方法统计。HotSpot compilation method statistics. |
2、操作
（1）
| class | class loader的行为统计。Statistics on the behavior of the class loader. |
（2）
| compiler | HotSpt JIT编译器行为统计。Statistics of the behavior of the HotSpot Just-in-Time compiler. |
（3）
| gc | 垃圾回收堆的行为统计。Statistics of the behavior of the garbage collected heap. |
（4）
| gccapacity | 各个垃圾回收代容量(young,old,perm)和他们相应的空间统计。Statistics of the capacities of the generations and their corresponding spaces. |
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