JVM 实践：jps、jinfo、jstat 命令详解

2012-05-09

背景

JVM 性能调优、问题排查过程中，常用几个命令，逐个分析一下细节：

jps：获取 jvm 进程的列表，获取 pid，jvm process status，类似 ps
jinfo：运行环境参数，Java System 属性、JVM 命令参数，class path 等
jstat：JVM 运行状态信息，类加载、内存回收等
jstack：JVM 进程内部，所有线程的运行情况

jps 命令

jps 命令的作用：查看有权限访问的 JVM 进程列表。

常用操作：

# 输出：
# 1. pid
# 2. 完整的 main Class 类名
# 3. main 入口参数
# 4. jvm 启动参数

jps -lmv

命令的详细介绍：

jps [ options ] [ hostid ]

options

jps 命令，可以配置的几个选项：

-l：显示，完整的 main Class 类名
-m：显示，main 函数的入口参数
-v：显示，JVM 启动参数

示例：

[root@ningg ~]# jps
12593 Main
45370 Jps


[root@ningg ~]# jps -l
12593 org.jruby.Main
45518 sun.tools.jps.Jps


[root@ningg ~]# jps -m
12593 Main /usr/share/logstash/lib/bootstrap/environment.rb logstash/runner.rb --path.settings /etc/logstash --node.name mini.ningg.top
45751 Jps -m


[root@ningg ~]# jps -v
12593 Main -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:+DisableExplicitGC -Djava.awt.headless=true -Dfile.encoding=UTF-8 -XX:+HeapDumpOnOutOfMemoryError -Xmx1g -Xms256m -Xss2048k -Djffi.boot.library.path=/usr/share/logstash/vendor/jruby/lib/jni -Xbootclasspath/a:/usr/share/logstash/vendor/jruby/lib/jruby.jar -Djruby.home=/usr/share/logstash/vendor/jruby -Djruby.lib=/usr/share/logstash/vendor/jruby/lib -Djruby.script=jruby -Djruby.shell=/bin/sh
46152 Jps -Dapplication.home=/usr/java/jdk1.8.0_131 -Xms8m

hostid

需要说明的几个细节：

jps 默认，查询 本机 的 JVM 进程列表
jps 也可以查询 远端服务器 的 JVM 进程列表
- 上述 hostid 就是远端服务器的地址
- 一般要求 远端服务器 上运行 jstatd 进程

jinfo 命令

jinfo 命令：运行环境参数，Java System 属性、JVM 命令参数，class path 等

常用操作：

# 输出：
# a. Java System 属性
# b. JVM 命令参数
# c. class path 信息
jinfo [pid]

命令详细介绍：

jinfo [ option ] pid

option

具体几个选项：

no option：同时输出 JVM 配置和命令行参数和 Java System 属性
-flags：JVM 配置和命令行参数
-sysprops：Java System 属性

补充信息：下述选项，属于慎重设置的选项

-flag [args]：查询指定参数的取值
-flag [+|-]name：开启 or 关闭某个 bool 类型参数
-flag name=value：设置某个取值类型参数

特别说明：

有些参数 支持 jinfo 命令 设置，有些参数，不支持 jinfo 命令 设置。

使用下述命令，查询哪些 JVM 参数可以设置：

# java -XX:+PrintFlagsFinal -version |grep 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_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

备注： java -XX:+PrintFlagsFinal -version 命令，表示输出所有参数.

示例

jinfo 命令的具体输出信息

flags

具体示例：

$ jinfo -flags 44736
Attaching to process ID 44736, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.131-b11
Non-default VM flags: -XX:CICompilerCount=4 -XX:InitialHeapSize=268435456 -XX:MaxHeapSize=4294967296 -XX:MaxNewSize=1431306240 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=89128960 -XX:OldSize=179306496 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:+UseParallelGC
Command line:  -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:55041,suspend=y,server=n -Dfile.encoding=UTF-8

上述信息，输出了：

JVM 配置： flags
JVM 命令参数： Command line

sysprops

具体示例：

$ jinfo -sysprops 44736
Attaching to process ID 44736, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.131-b11
java.runtime.name = Java(TM) SE Runtime Environment
java.vm.version = 25.131-b11
sun.boot.library.path = /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib
gopherProxySet = false
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 = CN
user.dir = /Users/guoning/ningg/github/jvm
java.vm.specification.name = Java Virtual Machine Specification
java.runtime.version = 1.8.0_131-b11
java.awt.graphicsenv = sun.awt.CGraphicsEnvironment
os.arch = x86_64
java.endorsed.dirs = /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/endorsed
java.io.tmpdir = /var/folders/w1/28b687hj1n1cngq28t956tzm0000gp/T/
line.separator =

java.vm.specification.vendor = Oracle Corporation
os.name = Mac OS X
sun.jnu.encoding = UTF-8
java.library.path = /Users/guoning/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.
java.specification.name = Java Platform API Specification
java.class.version = 52.0
sun.management.compiler = HotSpot 64-Bit Tiered Compilers
os.version = 10.13.4
user.home = /Users/guoning
user.timezone =
java.awt.printerjob = sun.lwawt.macosx.CPrinterJob
file.encoding = UTF-8
java.specification.version = 1.8
user.name = guoning
java.class.path = /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/tools.jar:/Users/guoning/ningg/github/jvm/target/classes:/Users/guoning/.m2/repository/junit/junit/4.12/junit-4.12.jar:/Users/guoning/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar
java.vm.specification.version = 1.8
sun.arch.data.model = 64
sun.java.command = top.ningg.java.App
java.home = /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre
user.language = zh
java.specification.vendor = Oracle Corporation
user.language.format = en
awt.toolkit = sun.lwawt.macosx.LWCToolkit
java.vm.info = mixed mode
java.version = 1.8.0_131
java.ext.dirs = /Users/guoning/Library/Java/Extensions:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java
sun.boot.class.path = /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/sunrsasign.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/classes
java.vendor = Oracle Corporation
file.separator = /
java.vendor.url.bug = http://bugreport.sun.com/bugreport/
sun.io.unicode.encoding = UnicodeBig
sun.cpu.endian = little
sun.cpu.isalist =

关注几个信息：

java.class.path：类加载路径
java.vm.info：JVM 的模式，一般都为混合模式
java.home：Java 安装路径

jstat 命令

下文所有内容，都是针对 JDK8 来描述的

jstat命令：查看堆内存使用情况，以及加载类的数量。

命令的格式如下：

jstat [-命令选项] [vmid] [间隔时间/毫秒] [查询次数]

其中，选项：

-h n：每输出 n 行，就输出一行 header
class: Displays statistics about the behavior of the class loader.
compiler: Displays statistics about the behavior of the Java HotSpot VM Just-in-Time compiler.
gc: Displays statistics about the behavior of the garbage collected heap.
gccapacity: Displays statistics about the capacities of the generations and their corresponding spaces.
gccause: Displays a summary about garbage collection statistics (same as -gcutil), with the cause of the last and current (when applicable) garbage collection events.
gcnew: Displays statistics of the behavior of the new generation.
gcnewcapacity: Displays statistics about the sizes of the new generations and its corresponding spaces.
gcold: Displays statistics about the behavior of the old generation and metaspace statistics.
gcoldcapacity: Displays statistics about the sizes of the old generation.
gcmetacapacity: Displays statistics about the sizes of the metaspace.
gcutil: Displays a summary about garbage collection statistics.
printcompilation: Displays Java HotSpot VM compilation method statistics.

几个术语：

S0：survivor space 0，新生代-幸存者0区
S1：survivor space 1，新生代-幸存者1区
S0C：S0 Capacity (kB)
S0U：S0 Utilization (kB)
E：eden space，新生代-伊甸区
O：old space，老年代
M：Metaspace，元数据区
CCS：Compressed class space，压缩类空间
YGC：Number of young generation garbage collection events，年轻代 Young GC 的次数
YGCT：Young generation garbage collection time，年轻代 Young GC 累计时间（s）
FGC: Number of full GC events，老年代 Full GC 的次数
FGCT: Full garbage collection time，老年代 Full GC 的累计时间（s）
GCT: Total garbage collection time，累计 GC 的时间
MN：Minimum，最小的
MX：Maximum，最大的
OGCMN：Old Generation Capacity MN，老年代容量的最大取值（kB）
LGCC：Cause of last garbage collection，最后一次 GC 的原因
GCC：Cause of current garbage collection，当前 GC 的原因

几个常用命令：

# 查询 GC 基本情况，以及 GC 次数和 GC 累计时间（s）
jstat -gc -h5 [pid] 1s 20

# 查询 GC 基本情况，容量使用情况
jstat -gcutil -h5 [pid] 1s 20

# 查询「堆」空间分配情况，最大值、最小值、当前值，以及是否在动态扩容
jstat -gccapacity -h5 [pid] 1s 20

更多细节，参考：jstat-Java Platform, Standard Edition Tools Reference

jstack

jstack 命令：JVM 进程内部，所有线程的运行情况

命令详细介绍：

jstack [pid]

附录

JVM 模式

查询 JVM 版本：java -version 通常会出现 mixed mode 是什么含义？

JVM有以下 2 种模式：

-Xmixed ：默认，混合模式（编译器、解释器）
-Xint：解释器模式

使用下述命令，可以验证：

$ java -Xint -version
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, interpreted mode)

$ java -version
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

备注：通过 java -X 可以查看基本所有的命令.

-Xint：代表解释模式(interpreted mode)

解释方式执行所有的字节码
执行速度慢，通常低10倍或更多

-Xmixed代表混合模式(mixed mode)：

JVM的默认工作模式
同时使用编译模式和解释模式
对于字节码中多次被调用的部分，JVM会将其编译成本地代码以提高执行效率；
而被调用很少（甚至只有一次）的方法在解释模式下会继续执行，从而减少编译和优化成本。
JIT编译器在运行时创建方法使用文件，然后一步一步的优化每一个方法，有时候会主动的优化应用的行为。这些优化技术，比如积极的分支预测（optimistic branch prediction），如果不先分析应用就不能有效的使用。这样将频繁调用的部分提取出来，编译成本地代码，也就是在应用中构建某种热点（即HotSpot，这也是HotSpot JVM名字的由来）；
使用混合模式可以获得最好的执行效率；

原文地址：https://ningg.top/jvm-best-practice-cmd-details-jps-jinfo-jstat/

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