JVM - 列出JVM默认参数及运行时生效参数

分手后的思念是犯贱 2023-02-23 08:26 17阅读 0赞

### 文章目录 ###

*  Pre
 *  \-XX:+PrintFlagsInitial 列出JVM参数的默认值
 *  \-XX:+PrintFlagsFinal 列出运行程序时生效的值
 *  \-XX:+PrintCommandLineFlags 列出被用户或者JVM优化设置过的详细的XX参数的名称和值
 *  列举附加隐藏参数
 *  jinfo 查看正在运行的Java应用程序的扩展参数
 *   *  jps
     *  jinfo

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]

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# Pre #

有的时候，想看下自己没有设置的JVM参数的值， 或者有的时候想看下JVM某个参数的默认值 ，亦或想看下用户或者JVM修改的JVM参数 ？

咋办 ？

JVM在1.6.0\_14以后提供了几个参数可以打印出来所有XX参数和对应的值

-XX:+PrintFlagsInitial 表示打印出所有参数选项的默认值
     -XX:+PrintFlagsFinal 表示打印出所有参数选项在运行程序时生效的值

执行的话

java -XX:+PrintFlagsInitial
    java -XX:+PrintFlagsFinal

--------------------

# \-XX:+PrintFlagsInitial 列出JVM参数的默认值 #

Java诞生了25年+， N多个参数 ，鬼记得住~

我们只需要直到常用的，会找就可以了。

我这用的1.8.0\_181 列举出了 866个

部分截图如下

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 1]

*  第一列表示参数的数据类型
 *  第二列是名称
 *   第三列”=”表示第四列是参数的默认值，如果是”:=” 表明了参数被用户或者JVM赋值了
 *  第四列为值
 *  第五列是参数的类别

--------------------

# \-XX:+PrintFlagsFinal 列出运行程序时生效的值 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 2]  
”:=” 表明了参数被用户或者JVM赋值了， 也间接证明了Java8默认的垃圾回收器是Parallel + Parallel Old .

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 3]

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# \-XX:+PrintCommandLineFlags 列出被用户或者JVM优化设置过的详细的XX参数的名称和值 #

这一步其实就是列出 `-XX:+PrintFlagsFinal`的结果中第三列有":="的参数 。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 4]

也可以理解为打印命令行参数

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# 列举附加隐藏参数 #

-XX:+UnlockDiagnosticVMOptions  解锁诊断参数
    
    -XX:+UnlockExperimentalVMOptions   解锁实验参数
    
    -XX:+UnlockInternalVMOptions 解锁内部参数

这个就是隐藏副本了 ，愿君多留意~

--------------------

# jinfo 查看正在运行的Java应用程序的扩展参数 #

当然了 还有其他参数 也可以看

jps + jinfo

--------------------

## jps ##

[root@artisan ~]# jps --help
    illegal argument: --help
    usage: jps [-help]
           jps [-q] [-mlvV] [<hostid>]
    
    Definitions:
        <hostid>:      <hostname>[:<port>]

最常用的jps , 查看PID

输出更多信息

jps -v

【demo】

[root@artisan ~]# jps
    5811 kooteam.jar
    6043 Jps
    [root@artisan ~]# jps -v
    5811 kooteam.jar -Xms1024m -Xmx1024m
    6054 Jps -Denv.class.path=.:/usr/java/jdk1.8.0_221-amd64/jre/lib:/usr/java/jdk1.8.0_221-amd64/lib:/usr/java/jdk1.8.0_221-amd64/lib/tools.jar -Dapplication.home=/usr/java/jdk1.8.0_221-amd64 -Xms8m
    [root@artisan ~]#

--------------------

## jinfo ##

[root@artisan ~]# 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
    [root@artisan ~]#

【查看jvm的参数】

[root@artisan ~]# jinfo -flags 5811
    Attaching to process ID 5811, please wait...
    Debugger attached successfully.
    Server compiler detected.
    JVM version is 25.221-b11
    Non-default VM flags: -XX:CICompilerCount=2 -XX:InitialHeapSize=1073741824 -XX:MaxHeapSize=1073741824 -XX:MaxNewSize=357892096 -XX:MinHeapDeltaBytes=196608 -XX:NewSize=357892096 -XX:OldSize=715849728 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps 
    Command line:  -Xms1024m -Xmx1024m
    [root@artisan ~]#

【查看java系统参数】

[root@artisan ~]# jinfo -sysprops  5811
    Attaching to process ID 5811, please wait...
    Debugger attached successfully.
    Server compiler detected.
    JVM version is 25.221-b11
    java.runtime.name = Java(TM) SE Runtime Environment
    java.vm.version = 25.221-b11
    sun.boot.library.path = /usr/java/jdk1.8.0_221-amd64/jre/lib/amd64
    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
    sun.os.patch.level = unknown
    sun.java.launcher = SUN_STANDARD
    user.country = US
    user.dir = /root
    java.vm.specification.name = Java Virtual Machine Specification
    java.runtime.version = 1.8.0_221-b11
    java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment
    os.arch = amd64
    java.endorsed.dirs = /usr/java/jdk1.8.0_221-amd64/jre/lib/endorsed
    line.separator = 
    
    java.io.tmpdir = /tmp
    java.vm.specification.vendor = Oracle Corporation
    os.name = Linux
    sun.jnu.encoding = UTF-8
    java.library.path = /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
    sun.nio.ch.bugLevel = 
    java.specification.name = Java Platform API Specification
    java.class.version = 52.0
    sun.management.compiler = HotSpot 64-Bit Tiered Compilers
    os.version = 3.10.0-123.el7.x86_64
    user.home = /root
    user.timezone = Asia/Shanghai
    java.awt.printerjob = sun.print.PSPrinterJob
    file.encoding = UTF-8
    java.specification.version = 1.8
    user.name = root
    java.class.path = ./kooteam.jar
    java.vm.specification.version = 1.8
    sun.arch.data.model = 64
    sun.java.command = ./kooteam.jar
    java.home = /usr/java/jdk1.8.0_221-amd64/jre
    user.language = en
    java.specification.vendor = Oracle Corporation
    awt.toolkit = sun.awt.X11.XToolkit
    java.vm.info = mixed mode
    java.version = 1.8.0_221
    java.ext.dirs = /usr/java/jdk1.8.0_221-amd64/jre/lib/ext:/usr/java/packages/lib/ext
    sun.boot.class.path = /usr/java/jdk1.8.0_221-amd64/jre/lib/resources.jar:/usr/java/jdk1.8.0_221-amd64/jre/lib/rt.jar:/usr/java/jdk1.8.0_221-amd64/jre/lib/sunrsasign.jar:/usr/java/jdk1.8.0_221-amd64/jre/lib/jsse.jar:/usr/java/jdk1.8.0_221-amd64/jre/lib/jce.jar:/usr/java/jdk1.8.0_221-amd64/jre/lib/charsets.jar:/usr/java/jdk1.8.0_221-amd64/jre/lib/jfr.jar:/usr/java/jdk1.8.0_221-amd64/jre/classes
    java.vendor = Oracle Corporation
    com.zaxxer.hikari.pool_number = 1
    file.separator = /
    java.vendor.url.bug = http://bugreport.sun.com/bugreport/
    sun.io.unicode.encoding = UnicodeLittle
    sun.cpu.endian = little
    sun.cpu.isalist = 
    [root@artisan ~]#

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200706155704737.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/2020070615583877.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ==,size_16,color_FFFFFF,t_70
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