jvm参数

jvm常见参数类型

1. 标配参数 如Java -version
2. -X参数
3. -XX参数 我们jvm调优时主要调的就是这类参数

如何查看当前的jvm参数
1.首先查看java应用的进程Id:
jps -l

E:\spring-boot\spring-boot-quickstart>jps -l
10016 org.jetbrains.jps.cmdline.Launcher
7252 org.jetbrains.idea.maven.server.RemoteMavenServer
10520 sun.tools.jps.Jps
10680 org.jetbrains.jps.cmdline.Launcher
12152 com.demo.springbootquickstart.SpringBootQuickstartApplication
12248 org.jetbrains.jps.cmdline.Launcher
2920

根据进程id,可用如下方式指定查看
jinfo -flag PrintGCDetails 12152

E:\spring-boot\spring-boot-quickstart>jinfo -flag PrintGCDetails 12152
-XX:+PrintGCDetails

查看所有
jinfo -flags 2488

E:\spring-boot\spring-boot-quickstart>jinfo -flags 2488
Attaching to process ID 2488, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.201-b09
Non-default VM flags: -XX:-BytecodeVerificationLocal -XX:-BytecodeVerificationRemote -XX:CICompilerCount=3 -XX:InitialHeapSize=134217728 -XX:+ManagementServer -XX:MaxHeapSize=2126512128 -XX:MaxNewSize=708837376 -XX:MetaspaceSize
=134217728 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=44564480 -XX:OldSize=89653248 -XX:TieredStopAtLevel=1 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:-UseLargePagesIndividualAllocat
ion -XX:+UseParallelGC
Command line:  -XX:MetaspaceSize=128m -XX:TieredStopAtLevel=1 -Xverify:none -Dspring.output.ansi.enabled=always -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=51823 -Dcom.sun.management.jmxremote.authenticate
=false -Dcom.sun.management.jmxremote.ssl=false -Djava.rmi.server.hostname=localhost -Dspring.liveBeansView.mbeanDomain -Dspring.application.admin.enabled=true -javaagent:E:\Idea\IntelliJ IDEA 2018.2.3\lib\idea_rt.jar=51824:E:\I
dea\IntelliJ IDEA 2018.2.3\bin -Dfile.encoding=UTF-8

面试中的坑题
Xms Xmx属于哪一种参数类型？Xms  Xmx其实类似数据库别名，Xms等价于InitialHeapSize  Xmx等价于MaxHeapSize