添加 JVM 参数选项

淩亂°似流年 2022-09-10 05:14 182阅读 0赞

# 一 IDE #

Eclipse 和 IDEA 中配置简单，在 Run Configurations 中 VM Options 中配置即可，大同小异。

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAY2hlbmdxaXVtaW5n_size_20_color_FFFFFF_t_70_g_se_x_16][]

# 二 运行 jar 包 #

> java -Xms100m -Xmx100m -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -jar demo.jar

# 三 Tomcat 运行 war 包 #

> \# Linux 下 tomcat/bin/catalina.sh 添加
> 
> JAVA\_OPTS="-Xms512M -Xmx1024M"
> 
> \# windows下 catalina.bat 添加
> 
> set "JAVA\_OPTS=-Xms512M -Xmx1024M"

# 四 程序运行过程中 #

> \# 设置Boolean类型参数
> 
> jinfo -flag \[+|-\]<name> <pid>
> 
> \# 设置非Boolean类型参数
> 
> jinfo -flag <name>=<value> <pid>

# 五 实战——运行过程中，哪些参数选项可以被修改 #

E:\JVMDemo3>jps
    7408 Jps
    7300 RemoteMavenServer36
    8356 Launcher
    10364 OOMTest
    7356
    
    # 查看某个数值型参数
    E:\JVMDemo3>jinfo -flag InitialHeapSize 10364
    -XX:InitialHeapSize=251658240
    
    # 运行时，InitialHeapSize 参数不能被修改
    E:\JVMDemo3>jinfo -flag InitialHeapSize=10000 10364
    Exception in thread "main" com.sun.tools.attach.AttachOperationFailedException: flag 'InitialHeapSize' cannot be changed
            at sun.tools.attach.WindowsVirtualMachine.execute(WindowsVirtualMachine.java:117)
            at sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:261)
            at sun.tools.attach.HotSpotVirtualMachine.setFlag(HotSpotVirtualMachine.java:234)
            at sun.tools.jinfo.JInfo.flag(JInfo.java:134)
            at sun.tools.jinfo.JInfo.main(JInfo.java:81)
    
    # 查看某个布尔型参数
    E:\JVMDemo3>jinfo -flag UseG1GC 10364
    -XX:-UseG1GC
    
    # 运行时，UseG1GC 参数不能被修改
    E:\JVMDemo3>jinfo -flag +UseG1GC 10364
    Exception in thread "main" com.sun.tools.attach.AttachOperationFailedException: flag 'UseG1GC' cannot be changed
            at sun.tools.attach.WindowsVirtualMachine.execute(WindowsVirtualMachine.java:117)
            at sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:261)
            at sun.tools.attach.HotSpotVirtualMachine.setFlag(HotSpotVirtualMachine.java:234)
            at sun.tools.jinfo.JInfo.flag(JInfo.java:140)
            at sun.tools.jinfo.JInfo.main(JInfo.java:81)
    
    # 运行中能被修改的参数很少，仅下面这些
    E:\JVMDemo3>java -XX:+PrintFlagsFinal -version|find "manageable"
         intx CMSAbortablePrecleanWaitMillis            = 100                                 {manageable}
         intx CMSTriggerInterval                        = -1                                  {manageable}
         intx CMSWaitDuration                           = 2000                                {manageable}
         bool HeapDumpAfterFullGC                       = false                               {manageable}
         bool HeapDumpBeforeFullGC                      = false                               {manageable}
         bool HeapDumpOnOutOfMemoryError                = false                               {manageable}
        ccstr HeapDumpPath                              =                                     {manageable}
        uintx MaxHeapFreeRatio                          = 100                                 {manageable}
        uintx MinHeapFreeRatio                          = 0                                   {manageable}
         bool PrintClassHistogram                       = false                               {manageable}
         bool PrintClassHistogramAfterFullGC            = false                               {manageable}
         bool PrintClassHistogramBeforeFullGC           = false                               {manageable}
         bool PrintConcurrentLocks                      = false                               {manageable}
         bool PrintGC                                   = false                               {manageable}
         bool PrintGCDateStamps                         = false                               {manageable}
         bool PrintGCDetails                            = false                               {manageable}
         bool PrintGCID                                 = false                               {manageable}
         bool PrintGCTimeStamps                         = false                               {manageable}
    java version "1.8.0_251"
    Java(TM) SE Runtime Environment (build 1.8.0_251-b08)
    Java HotSpot(TM) 64-Bit Server VM (build 25.251-b08, mixed mode)
    
    # 运行中，HeapDumpAfterFullGC 可以被修改
    E:\JVMDemo3>jinfo -flag HeapDumpAfterFullGC 10364
    -XX:-HeapDumpAfterFullGC
    
    E:\JVMDemo3>jinfo -flag +HeapDumpAfterFullGC 10364
    
    E:\JVMDemo3>jinfo -flag HeapDumpAfterFullGC 10364
    -XX:+HeapDumpAfterFullGC
    
    # 运行中，HeapDumpPath 可以被修改
    E:\JVMDemo3>jinfo -flag HeapDumpPath 10364
    -XX:HeapDumpPath=
    
    E:\JVMDemo3>jinfo -flag HeapDumpPath=d:/ 10364
    
    E:\JVMDemo3>jinfo -flag HeapDumpPath 10364
    -XX:HeapDumpPath=d:/

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