JVM性能优化指南
JVM常用命令
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jps
查看java进程
The jps command lists the instrumented Java HotSpot VMs on the target system. The command is limited to reporting information on JVMs for which it has the access permissions.
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jinfo
（1）实时查看和调整JVM配置参数
The jinfo command prints Java configuration information for a specified Java process or core file or a remote debug server. The configuration information includes Java system properties and Java Virtual Machine (JVM) command-line flags.
（2）查看用法
jinfo -flag name PID 查看某个java进程的name属性的值
jinfo -flag MaxHeapSize PID jinfo -flag UseG1GC PID
3）修改
参数只有被标记为manageable的flags可以被实时修改
jinfo -flag [+|-] PID jinfo -flag <name>=<value> PID
（4）查看曾经赋过值的一些参数
jinfo -flags PID
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jstat
（1）查看虚拟机性能统计信息
The jstat command displays performance statistics for an instrumented Java HotSpot VM. The target JVM is identified by its virtual machine identifier, or vmid option.
（2）查看类装载信息
jstat -class PID 1000 10 查看某个java进程的类装载信息，每1000毫秒输出一次，共输出10次
（3）查看垃圾收集信息
jstat -gc PID 1000 10
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jstack
（1）查看线程堆栈信息
The jstack command prints Java stack traces of Java threads for a specified Java process, core file, or remote debug server.
（2）用法
jstack PID
知识来源：马士兵教育
