JVM調優中經常用到的幾個命令
阿新 • • 發佈：2019-01-23
jcmd-查詢jvm程序資訊
jcmd命令預設是查詢jvm程序資訊，也可以執行相關的jvm命令。
幫助資訊
F:\soft\Java\jdk1.8\bin>jcmd -h
Usage: jcmd <pid | main class> <command ...|PerfCounter.print|-f file>
or: jcmd -l
or: jcmd -h
command must be a valid jcmd command for the selected jvm.
Use the command "help" to see which commands are available.
If the 使用例項 1
F:\soft\Java\jdk1.8\bin>jcmd
3068 sun.tools.jcmd.JCmd使用示例 2
使用命令：
jcmd 9816 PerfCounter.print可詳細列印對應java程序的有效效能計數器(performance counters)。
9816:
java.ci.totalTime=106668
java.cls 診斷命令
診斷命令的幫助資訊
D:\>jcmd 9816 help
9816:
The following commands are available:
JFR.stop
JFR.start
JFR.dump
JFR.check
VM.native_memory
VM.check_commercial_features
VM.unlock_commercial_features
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
GC.rotate_log
Thread.print
GC.class_stats
GC.class_histogram
GC.heap_dump
GC.run_finalization
GC.run
VM.uptime
VM.flags
VM.system_properties
VM.command_line
VM.version
help
For more information about a specific command use 'help <command>'.其中9816是某個jvm程序的pid。
具體診斷命令的幫助
如下是GC.run診斷命令的幫助資訊。
D:\>jcmd 9816 help GC.run
9816:
GC.run
Call java.lang.System.gc().
Impact: Medium: Depends on Java heap size and content.
Syntax: GC.run診斷命令的應用
GC.run診斷命令
診斷前：
D:\>jstat -gcutil 9816 500 7
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000
0.00 0.00 24.05 0.00 16.66 19.75 0 0.000 0 0.000 0.000進行診斷操作：
D:\>jcmd 9816 GC.run
9816:
Command executed successfully診斷後：
D:\>jstat -gcutil 9816 500 7
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006
0.00 0.00 0.00 1.21 79.67 87.24 1 0.001 1 0.004 0.006在診斷前後，請注意FGC(Full GC)的變化。
VM.flags診斷命令
此命令只是顯示JVM的引數資訊。
D:\>jcmd 9816 VM.flags
9816:
-XX:CICompilerCount=3 -XX:InitialHeapSize=134217728 -XX:MaxHeapSize=2120220672 -XX:MaxNewSize=706740224 -XX:MinHeapDelta
Bytes=524288 -XX:NewSize=44564480 -XX:OldSize=89653248 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFa
stUnorderedTimeStamps -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC還有更多有用的診斷命令，請自己查驗。
## jinfo-檢視系統資訊和JVM資訊
### 幫助資訊
主要的引數是-flags列印JVM的資訊和-sysprops列印系統的資訊。F:\soft\Java\jdk1.8\bin>jinfo
Usage:
jinfo [option]
(to connect to running process)
jinfo [option]
### 使用例項F:\soft\Java\jdk1.8\bin>jinfo 5952
Attaching to process ID 5952, please wait…
Debugger attached successfully.
Server compiler detected.
JVM version is 25.101-b13
Java System Properties:
java.runtime.name = Java(TM) SE Runtime Environment
java.vm.version = 25.101-b13
sun.boot.library.path = F:\soft\Java\jre1.8\bin
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 = Service Pack 1
sun.java.launcher = SUN_STANDARD
user.script =
user.country = CN
user.dir = D:\web_work\boss\target
java.vm.specification.name = Java Virtual Machine Specification
java.runtime.version = 1.8.0_101-b13
java.awt.graphicsenv = sun.awt.Win32GraphicsEnvironment
os.arch = amd64
java.endorsed.dirs = F:\soft\Java\jre1.8\lib\endorsed
line.separator =
java.io.tmpdir = C:\Users\MICHAE~1\AppData\Local\Temp\
java.vm.specification.vendor = Oracle Corporation
user.variant =
os.name = Windows 7
sun.jnu.encoding = GBK
java.library.path = C:\ProgramData\Oracle\Java\javapath;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;C:\Progra
mData\Oracle\Java\javapath;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell
\v1.0\;D:\soft\svn\bin;F:\soft\Java\jdk1.8\bin;E:\DTool\sdk\platform-tools;E:\DTool\sdk\tools;%MAVEN_HOME%\bin;D:\apache
-maven-3.3.9\bin;D:\soft\MySQL\MySQLServer\bin;D:\as\gradle\gradle-2.14.1\bin;H:\php56\;H:\php56\ext;H:\DownLoad\apache-
ant-1.10.1\bin;F:\Program Files\Git\cmd;F:\Program Files\Git\mingw64\bin;F:\Program Files\Git\usr\bin;F:\Program Files\V
isualSVN Server\bin;F:\soft\python3;F:\Program Files (x86)\AllWinnerTech\PhoenixSuit\;.
java.specification.name = Java Platform API Specification
java.class.version = 52.0
sun.management.compiler = HotSpot 64-Bit Tiered Compilers
os.version = 6.1
user.home = C:\Users\MichaelKoo
user.timezone =
java.awt.printerjob = sun.awt.windows.WPrinterJob
file.encoding = GBK
java.specification.version = 1.8
user.name = MichaelKoo
java.class.path = boss-1.0.1.jar
java.vm.specification.version = 1.8
sun.arch.data.model = 64
sun.java.command = boss-1.0.1.jar 2 124.42.243.67 8010
java.home = F:\soft\Java\jre1.8
user.language = zh
java.specification.vendor = Oracle Corporation
awt.toolkit = sun.awt.windows.WToolkit
java.vm.info = mixed mode
java.version = 1.8.0_101
java.ext.dirs = F:\soft\Java\jre1.8\lib\ext;C:\Windows\Sun\Java\lib\ext
sun.boot.class.path = F:\soft\Java\jre1.8\lib\resources.jar;F:\soft\Java\jre1.8\lib\rt.jar;F:\soft\Java\jre1.8\lib\sunrs
asign.jar;F:\soft\Java\jre1.8\lib\jsse.jar;F:\soft\Java\jre1.8\lib\jce.jar;F:\