java常用命令

1. 查看程序的jvm启动参数

jcmd 106179 VM.flags

-XX:CICompilerCount=3 -XX:CMSInitiatingOccupancyFraction=80 -XX:+DisableExplicitGC -XX:ErrorFile=/opt/logs/operation/operation.hs_err_%p.log -XX:GCLogFileSize=536870912 -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/opt/logs/operation/operation.heap_err_%p.hprof -XX:InitialCodeCacheSize=134217728 -XX:InitialHeapSize=536870912 -XX:MaxHeapSize=536870912 -XX:MaxMetaspaceSize=268435456 -XX:MaxNewSize=178913280 -XX:MetaspaceSize=268435456 -XX:MinHeapDeltaBytes=196608 -XX:NewRatio=2 -XX:NewSize=178913280 -XX:NumberOfGCLogFiles=5 -XX:OldPLABSize=16 -XX:OldSize=357957632 -XX:+PrintGC -XX:+PrintGCDateStamps -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:ReservedCodeCacheSize=134217728 -XX:SurvivorRatio=8 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseConcMarkSweepGC -XX:+UseFastUnorderedTimeStamps -XX:+UseGCLogFileRotation -XX:+UseParNewGC

 

2. 查看java相关程序，先切换到root或对应的用户下

jps

 

3. 查看gc 实时状态

jstat -gcutil 106179 5000 10

pid 106179 每5s打印一次，打印10次

4. 查看实时内存信息

/usr/local/java8/bin/jmap -heap 106179

 

5. 排查cpu使用问题

https://www.cnblogs.com/tankaixiong/p/5984023.html

https://www.cnblogs.com/liusxg/p/5811085.html