JVM调优命令-jinfo

jinfo

JVM Configuration info这个命令作用是实时查看和调整虚拟机运行参数。之前的jps -v口令只能查看到显示指定的参数，如果想要查看未被显示指定的参数的值就要使用jinfo口令。【JVM配置参数调整查看】

[root@localhost bin]# jinfo -help
Usage:
    jinfo [option] <pid>
        (to connect to running process)
    jinfo [option] <executable <core>
        (to connect to a core file)
    jinfo [option] [server_id@]<remote server IP or hostname>
        (to connect to remote debug server)
 
where <option> is one of:
    -flag <name>         to print the value of the named VM flag
    -flag [+|-]<name>    to enable or disable the named VM flag
    -flag <name>=<value> to set the named VM flag to the given value
    -flags               to print VM flags
    -sysprops            to print Java system properties
    <no option>          to print both of the above
    -h | -help           to print this help message

参数

-flag：输出指定args参数的值

-flags：输出所有JVM参数的值

-sysprops：输出系统属性，等同于System.getProperties()

示例

[root@localhost bin]# jinfo -sysprops 24971 | more
Attaching to process ID 24971, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.79-b02
java.runtime.name = Java(TM) SE Runtime Environment
java.vm.version = 24.79-b02
sun.boot.library.path = /usr/local/java/jdk1.7.0_79/jre/lib/amd64
shared.loader = 
java.vendor.url = http://java.oracle.com/
java.vm.vendor = Oracle Corporation
path.separator = :
file.encoding.pkg = sun.io
java.vm.name = Java HotSpot(TM) 64-Bit Server VM
java.util.logging.config.file = /home/yuhuo-tomcat/tomcat2/conf/logging.properties
tomcat.util.buf.StringCache.byte.enabled = true
sun.os.patch.level = unknown
sun.java.launcher = SUN_STANDARD
user.country = CN
user.dir = /home/yuhuo-tomcat/tomcat2/bin
java.vm.specification.name = Java Virtual Machine Specification
java.runtime.version = 1.7.0_79-b15
org.apache.catalina.startup.TldConfig.jarsToSkip = tomcat7-websocket.jar
java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment
os.arch = amd64

[root@localhost bin]# jinfo -flag MaxPermSize 24971
-XX:MaxPermSize=85983232