jdk工具之jinfo命令(Java Configuration Info)

jinfo

jinfo可以查看正在运行的 JVM 进程信息

语法

jinfo [option] <pid>

$ jinfo --help
Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
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

查看一个JVM进程的最大堆内存

# 这里的单位是 byte
$ jinfo -flag MaxHeapSize 13116
Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
-XX:MaxHeapSize=4271898624

-flags 查看非JVM默认参数信息

# 这里查看的是一个 spring cloud 的一个网关程序
$ jinfo -flags 12299
Attaching to process ID 12299, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.111-b14
# 不是 JVM 默认参数，被修改过
Non-default VM flags: -XX:CICompilerCount=3 -XX:InitialHeapSize=62914560 -XX:MaxHeapSize=1048576000 -XX:MaxNewSize=349175808 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=20971520 -XX:OldSize=41943040 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:+UseParallelGC 
# 这里是前几天我通过命令行运行程序的时候加上的 java -Xmx1000m -jar xxx
Command line:  -Xmx1000m

查看垃圾回收器

# 表示ConcMarkSweepGC是关闭状态的
$ jinfo -flag UseConcMarkSweepGC 12299
-XX:-UseConcMarkSweepGC
# 表示G1GC是关闭状态的
$ jinfo -flag UseG1GC 12299
-XX:-UseG1GC
# 表示ParallelGC是开启状态的
$ jinfo -flag UseParallelGC 12299
-XX:+UseParallelGC