Java启动参数

关键字：`java启动参数` `jvm启动参数`

```shell
java -X
java -XX:+PrintFlagsFinal -version
java -XX:+PrintCommandLineFlags -version
java -XX:+PrintFlagsInitial -version
```

```shell
-server -Xmx9g -Xms9g -Xmn3g -Xss500k -XX:+DisableExplicitGC -XX:MetaspaceSize=2048m -XX:MaxMetaspaceSize=2048m -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled -XX:LargePageSizeInBytes=128m -XX:+UseFastAccessorMethods -XX:+UseCMSInitiatingOccupancyOnly -XX:CMSInitiatingOccupancyFraction=70 -Dfile.encoding=UTF8 -Duser.timezone=GMT+08

' -Xdebug -Xrunjdwp:transport=dt_socket,address=5005,server=y,suspend=n -Xmx512m -Xms512m -Xss512k -XX:+UseG1GC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:MaxGCPauseMillis=200 -XX:InitiatingHeapOccupancyPercent=45 -Djava.io.tmpdir=/tmp -Xloggc:/workspace/logs/dev-wolf/wolf-app-analyzer/gc.log'
```

## gc log

before java11

https://docs.oracle.com/en/java/javase/11/jrockit-hotspot/logging.html

```text
-XX:+PrintGC
-XX:+PrintGCDetails
-XX:+PrintGCDateStamps
-XX:+PrintGCTimeStamps
```

after java11

```text
# https://docs.oracle.com/en/java/javase/11/tools/java.html
"-Xlog:gc*=info:file=/root/workbench/springboot-simple/gc-%t.log:time,level,tags:filecount=50,filesize=100m",

```