8.2 Common Commands
8.2.1 jps
View java process jps -l
8.2.2 jinfo
Real-time view and adjust JVM arguments
1) Check the name attribute of a java process
jinfo -flag MaxHeapSize PID
jinfo -flag UseG1GC PID
2) modify the parameters
Only marked as manageable the flag can be modified in real time
jinfo -flag [+|-] PID
jinfo -flag = PID
3) Check out some of the parameters have been assigned
jinfo -flags PID
8.2.3 jstat
1) Check VM performance statistics
2) See class loading information
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
jstat -class PID 1000 10
3) Check the garbage collection information
jstat -gc PID 1000 10
8.2.4 jstack
View thread stack information
jstack PID
8.2.5 jmap
Health heap dump snapshot
1) print out the heap memory information
-XX:PrintFlagsFinal -Xms300M -Xmx300M
jmap -heap PID
2) dump the heap memory information
jmap -dump:format=b,file=heap.hprof PID
3) Set heap memory overflow, automatic dump file
-XX:HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=heap.hprof
8.3 Common tools
8.3.1 jconsole
JConsole is JDK that comes with visual monitoring tool.
命令行输入：jconsole
8.3.2 jvisualvm
Monitoring can be local, remote java process CPU, class, thread
(1) Select the "Remote" in visualvm, right-click the "Add"
(2) the server's ip address written on a host name, such as 31.100.39.63, then click "OK"
(3) Right-click the host "31.100.39.63", adding "JMX" [that is, through JMX technology to monitor a remote server which specific Java process]
In the startup items plus the following parameters:
-Dcom.sun.management.jmxremote - Djava.rmi.server.hostname=31.100.39.63 -Dcom.sun.management.jmxremote.port=8998 -Dcom.sun.management.jmxremote.ssl=false - Dcom.sun.management.jmxremote.authenticate=true - Dcom.sun.management.jmxremote.access.file=../conf/jmxremote.access - Dcom.sun.management.jmxremote.password.file=../conf/jmxremote.password"
Create two files
jmxremote.access
guest readonly
manager readwrite
jmxremote.password
guest guest
manager manager
Grant permission: chmod 600 jmxremot
8.3.3 Arthas
Arthas is a diagnostic tool Alibaba Java open source, using the command line interactive mode,
Official website: https: //github.com/alibaba/arthas
8.3.3.1 download and install
curl -O https://alibaba.github.io/arthas/arthas-boot.jar
java -jar arthas-boot.jar
# 然后可以选择一个Java进程
Print usage
java -jar arthas-boot.jar -h
8.3.3.2 commonly used commands
version:查看arthas版本号
help:查看命名帮助信息
cls:清空屏幕
session:查看当前会话信息
quit:退出arthas客户端
---
dashboard:当前进程的实时数据面板
thread:当前JVM的线程堆栈信息
jvm:查看当前JVM的信息
sysprop:查看JVM的系统属性
---
sc:查看JVM已经加载的类信息
dump:dump已经加载类的byte code到特定目录
jad:反编译指定已加载类的源码
---
monitor:方法执行监控
watch:方法执行数据观测
trace:方法内部调用路径，并输出方法路径上的每个节点上耗时
stack:输出当前方法被调用的调用路径
......
8.3.4 MAT
java heap analyzer for finding memory leaks
Download: https://www.eclipse.org/mat/downloads.php
8.3.5 GC log analysis tool
-XX:+PrintGCDetails
-XX:+PrintGCTimeStamps
-XX:+PrintGCDateStamps
-Xloggc:gc.log
Online
- http://gceasy.io
GCViewer
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