常用的Java命令行工具的使用梳理,方便以后线上问题排查处理.
示例使用的虚拟机版本(JVM自带命令行工具在bin目录下)
[root@localhost ~]# java -version
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)
[root@localhost ~]# which java
/usr/local/jdk1.8.0_121/bin/java
[root@localhost ~]# ls /usr/local/jdk1.8.0_121/bin/ appletviewer jarsigner javah jcmd jhat jmc.ini jstat orbd rmiregistry unpack200 ControlPanel java javap jconsole jinfo jps jstatd pack200 schemagen wsgen extcheck javac javapackager jcontrol jjs jrunscript jvisualvm policytool serialver wsimport idlj javadoc java-rmi.cgi jdb jmap jsadebugd keytool rmic servertool xjc jar javafxpackager javaws jdeps jmc jstack native2ascii rmid tnameserv 常用Java命令行工具
- javap : java字节码信息查看工具
- jps : java虚拟机进程信息工具
- jinfo : java虚拟机进程配置信息工具
- jstat : java虚拟机进程统计信息监控工具
- jstack : java虚拟机进程堆栈跟踪工具, 制作线程Dump
- jmap : java虚拟机进程堆内存映射,制作堆Dump
- jhat : java虚拟机堆转储快照分析工具
- jconsole : 用于提供JVM活动的图形化视图,包括线程的使用、类的使用和GC活动.
- jvisualvm: 监控JVM的GUI工具,可用来剖析运行的应用,分析JVM堆转储.
术语认知
Java Dump介绍
Java虚拟机的运行时快照.将Java虚拟机运行时的状态和信息保存到文件, 用于补足传统Bug分析手段的不足,可在任何Java环境使用; 信息量充足;针对非功能正确性的Bug(像多线程幵发、内存泄漏)
- ThreadDump : 包含所有线程的运行状态.纯文本格式
- HeapDump: 包含线程Dump,幵包含所有堆对象的状态,二进制格式.
制作Java Dump
使用Java虚拟机配置
配置jvm参数 -XX:+HeapDumpOnOutOfMemoryError 让虚拟机在OOM异常出现之后自动生成dump文件.
配置jvm参数 -XX:+HeapDumpOnCtrlBreak 使用Ctrl+Break键,让虚拟机生成dump文件.
使用图形化工具
使用JDK自带工具: Java VisualVM
Linux系统下通过kill命令
Linux系统下通过kill -3 命令发送进程退出信号'吓唬'一下虚拟机,也能拿到dump文件.
使用Java命令行工具
- jstack:打印线程的栈信息,制作线程Dump.
- jmap:打印内存映射,制作堆Dump.
命令行工具-jps
jps(Jvm Process Status Tool) 虚拟机进程状态工具, 可以用于查看当前运行的java行程以及相关参数
jps语法
[root@localhost ~]# jps -help
usage: jps [-help]
jps [-q] [-mlvV] [<hostid>]
Definitions:
<hostid>: <hostname>[:<port>]
参数说明
- -q : 忽略输出的类名、Jar名以及传递给main方法的参数,只输出pid
- -m : 输出虚拟机进程启动时传递给主类main()方法的参数
- -l : 输出主类完整的包名和类名,如果进程执行的是jar包,输出jar包路径
- -v : 输出虚拟机进程启动时jvm参数
- -V : 输出通过标记的文件传递给JVM的参数(.hotspotrc文件,或者是通过参数-XX:Flags=指定的文件)
jps示例
输出Java进程pid
[root@localhost ~]# jps -q
3126
6940
输出主类包名和类名
[root@localhost ~]# jps -l
3126 org.apache.catalina.startup.Bootstrap
6955 sun.tools.jps.Jps
输出进程启动时传递给主类的方法参数
[root@localhost ~]# jps -m
3126 Bootstrap start
6970 Jps -m
[root@localhost ~]# jps -lm
3126 org.apache.catalina.startup.Bootstrap start
6985 sun.tools.jps.Jps -lm
输出通过标记文件传递给Jvm的参数
[root@localhost ~]# jps -V
7011 Jps
3126 Bootstrap
[root@localhost ~]# jps -lV
7026 sun.tools.jps.Jps
3126 org.apache.catalina.startup.Bootstrap
输出进程启动时的jvm参数
[root@localhost ~]# jps -v
7073 Jps -Dapplication.home=/usr/local/jdk1.8.0_121 -Xms8m
3126 Bootstrap -Djava.util.logging.config.file=/usr/local/confluence-6.0.3/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE=32768 -Xms1536m -Xmx2048m -XX:+UseG1GC -Datlassian.plugins.enable.wait=300 -Djava.awt.headless=true -XX:G1ReservePercent=20 -Xloggc:/usr/local/confluence-6.0.3/logs/gc-2017-10-15_16-08-58.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M -XX:-PrintGCDetails -XX:+PrintGCDateStamps -XX:-PrintTenuringDistribution -Dhttp.socket.timeout=10 -Djava.endorsed.dirs=/usr/local/confluence-6.0.3/endorsed -Dcatalina.base=/usr/local/confluence-6.0.3 -Dcatalina.home=/usr/local/confluence-6.0.3 -Djava.io.tmpdir=/usr/local/confluence-6.0.3/temp [root@localhost ~]# jps -lv 7088 sun.tools.jps.Jps -Dapplication.home=/usr/local/jdk1.8.0_121 -Xms8m 3126 org.apache.catalina.startup.Bootstrap -Djava.util.logging.config.file=/usr/local/confluence-6.0.3/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE=32768 -Xms1536m -Xmx2048m -XX:+UseG1GC -Datlassian.plugins.enable.wait=300 -Djava.awt.headless=true -XX:G1ReservePercent=20 -Xloggc:/usr/local/confluence-6.0.3/logs/gc-2017-10-15_16-08-58.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M -XX:-PrintGCDetails -XX:+PrintGCDateStamps -XX:-PrintTenuringDistribution -Dhttp.socket.timeout=10 -Djava.endorsed.dirs=/usr/local/confluence-6.0.3/endorsed -Dcatalina.base=/usr/local/confluence-6.0.3 -Dcatalina.home=/usr/local/confluence-6.0.3 -Djava.io.tmpdir=/usr/local/confluence-6.0.3/temp [root@localhost ~]# jps -lmv 3126 org.apache.catalina.startup.Bootstrap start -Djava.util.logging.config.file=/usr/local/confluence-6.0.3/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE=32768 -Xms1536m -Xmx2048m -XX:+UseG1GC -Datlassian.plugins.enable.wait=300 -Djava.awt.headless=true -XX:G1ReservePercent=20 -Xloggc:/usr/local/confluence-6.0.3/logs/gc-2017-10-15_16-08-58.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M -XX:-PrintGCDetails -XX:+PrintGCDateStamps -XX:-PrintTenuringDistribution -Dhttp.socket.timeout=10 -Djava.endorsed.dirs=/usr/local/confluence-6.0.3/endorsed -Dcatalina.base=/usr/local/confluence-6.0.3 -Dcatalina.home=/usr/local/confluence-6.0.3 -Djava.io.tmpdir=/usr/local/confluence-6.0.3/temp 7103 sun.tools.jps.Jps -lmv -Dapplication.home=/usr/local/jdk1.8.0_121 -Xms8m 命令行工具-jinfo
jinfo(Configuration Info for Java) 作用是实时地查看和调整虚拟机各项参数.
jinfo语法
[root@localhost ~]# 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 jinfo示例
获取应用进程所有配置信息
[root@localhost ~]# jps -l
3126 org.apache.catalina.startup.Bootstrap
4076 sun.tools.jps.Jps
[root@localhost ~]# jinfo 3126
Attaching to process ID 3126, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.121-b13
Java System Properties:
java.vendor = Oracle Corporation
sun.java.launcher = SUN_STANDARD
catalina.base = /usr/local/confluence-6.0.3
sun.management.compiler = HotSpot 64-Bit Tiered Compilers
catalina.useNaming = true os.name = Linux java.util.logging.config.file = /usr/local/confluence-6.0.3/conf/logging.properties sun.boot.class.path = /usr/local/jdk1.8.0_121/jre/lib/resources.jar:/usr/local/jdk1.8.0_121/jre/lib/rt.jar:/usr/local/jdk1.8.0_121/jre/lib/sunrsasign.jar:/usr/local/jdk1.8.0_121/jre/lib/jsse.jar:/usr/local/jdk1.8.0_121/jre/lib/jce.jar:/usr/local/jdk1.8.0_121/jre/lib/charsets.jar:/usr/local/jdk1.8.0_121/jre/lib/jfr.jar:/usr/local/jdk1.8.0_121/jre/classes java.vm.specification.vendor = Oracle Corporation java.runtime.version = 1.8.0_121-b13 atlassian.plugins.enable.wait = 300 user.name = root shared.loader = tomcat.util.scan.StandardJarScanFilter.jarsToScan = log4j-web*.jar,log4j-taglib*.jar,log4javascript*.jar,slf4j-taglib*.jar com.sun.jndi.ldap.connect.pool.protocol = plain ssl com.sun.jndi.ldap.connect.pool.authentication = simple tomcat.util.buf.StringCache.byte.enabled = true user.language = zh java.naming.factory.initial = org.apache.naming.java.javaURLContextFactory sun.boot.library.path = /usr/local/jdk1.8.0_121/jre/lib/amd64 atlassian.enable.spring.strong.cache.bean.metadata = true jdk.tls.ephemeralDHKeySize = 2048 java.version = 1.8.0_121 java.util.logging.manager = org.apache.juli.ClassLoaderLogManager user.timezone = Asia/Shanghai sun.arch.data.model = 64 atlassian.enable.spring.strong.cache.bean.metadata.flush = true java.endorsed.dirs = /usr/local/confluence-6.0.3/endorsed sun.cpu.isalist = sun.jnu.encoding = UTF-8 file.encoding.pkg = sun.io org.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE = 32768 package.access = sun.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.tomcat. file.separator = / java.specification.name = Java Platform API Specification java.class.version = 52.0 user.country = CN java.home = /usr/local/jdk1.8.0_121/jre atlassian.org.osgi.framework.bootdelegation.extra = org.apache.lucene.* java.vm.info = mixed mode os.version = 3.10.0-514.6.1.el7.x86_64 com.sun.jndi.ldap.connect.pool.prefsize = 10 sun.font.fontmanager = sun.awt.X11FontManager path.separator = : java.vm.version = 25.121-b13 java.protocol.handler.pkgs = org.apache.catalina.webresources java.awt.printerjob = sun.print.PSPrinterJob sun.io.unicode.encoding = UnicodeLittle sun.java2d.opengl = true awt.toolkit = sun.awt.X11.XToolkit package.definition = sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.naming.,org.apache.tomcat. java.naming.factory.url.pkgs = org.apache.naming user.home = /root java.specification.vendor = Oracle Corporation tomcat.util.scan.StandardJarScanFilter.jarsToSkip = bootstrap.jar,commons-daemon.jar,tomcat-juli.jar,annotations-api.jar,el-api.jar,jsp-api.jar,servlet-api.jar,websocket-api.jar,catalina.jar,catalina-ant.jar,catalina-ha.jar,catalina-storeconfig.jar,catalina-tribes.jar,jasper.jar,jasper-el.jar,ecj-*.jar,tomcat-api.jar,tomcat-util.jar,tomcat-util-scan.jar,tomcat-coyote.jar,tomcat-dbcp.jar,tomcat-jni.jar,tomcat-websocket.jar,tomcat-i18n-en.jar,tomcat-i18n-es.jar,tomcat-i18n-fr.jar,tomcat-i18n-ja.jar,tomcat-juli-adapters.jar,catalina-jmx-remote.jar,catalina-ws.jar,tomcat-jdbc.jar,tools.jar,commons-beanutils*.jar,commons-codec*.jar,commons-collections*.jar,commons-dbcp*.jar,commons-digester*.jar,commons-fileupload*.jar,commons-httpclient*.jar,commons-io*.jar,commons-lang*.jar,commons-logging*.jar,commons-math*.jar,commons-pool*.jar,jstl.jar,taglibs-standard-spec-*.jar,geronimo-spec-jaxrpc*.jar,wsdl4j*.jar,ant.jar,ant-junit*.jar,aspectj*.jar,jmx.jar,h2*.jar,hibernate*.jar,httpclient*.jar,jmx-tools.jar,jta*.jar,log4j*.jar,mail*.jar,slf4j*.jar,xercesImpl.jar,xmlParserAPIs.jar,xml-apis.jar,junit.jar,junit-*.jar,ant-launcher.jar,cobertura-*.jar,asm-*.jar,dom4j-*.jar,icu4j-*.jar,jaxen-*.jar,jdom-*.jar,jetty-*.jar,oro-*.jar,servlet-api-*.jar,tagsoup-*.jar,xmlParserAPIs-*.jar,xom-*.jar java.library.path = /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib java.vendor.url = http://java.oracle.com/ java.vm.vendor = Oracle Corporation common.loader = "${catalina.base}/lib","${catalina.base}/lib/*.jar","${catalina.home}/lib","${catalina.home}/lib/*.jar" java.runtime.name = Java(TM) SE Runtime Environment sun.java.command = org.apache.catalina.startup.Bootstrap start java.class.path = /usr/local/confluence-6.0.3/bin/bootstrap.jar:/usr/local/confluence-6.0.3/bin/tomcat-juli.jar hibernate.bytecode.use_reflection_optimizer = true com.sun.jndi.ldap.connect.pool.maxsize = 0 java.vm.specification.name = Java Virtual Machine Specification java.vm.specification.version = 1.8 catalina.home = /usr/local/confluence-6.0.3 sun.cpu.endian = little sun.os.patch.level = unknown java.awt.headless = true java.io.tmpdir = /usr/local/confluence-6.0.3/temp java.vendor.url.bug = http://bugreport.sun.com/bugreport/ server.loader = os.arch = amd64 java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment java.ext.dirs = /usr/local/jdk1.8.0_121/jre/lib/ext:/usr/java/packages/lib/ext user.dir = / com.sun.jndi.ldap.connect.pool.initsize = 1 line.separator = java.vm.name = Java HotSpot(TM) 64-Bit Server VM file.encoding = UTF-8 com.sun.jndi.ldap.connect.pool.timeout = 30000 http.socket.timeout = 10 java.specification.version = 1.8 plugin.webresource.javascript.try.catch.wrapping = true VM Flags: Non-default VM flags: -XX:CICompilerCount=3 -XX:ConcGCThreads=1 -XX:G1HeapRegionSize=1048576 -XX:G1ReservePercent=20 -XX:GCLogFileSize=2097152 -XX:InitialHeapSize=1610612736 -XX:MarkStackSize=4194304 -XX:MaxHeapSize=2147483648 -XX:MaxNewSize=1287651328 -XX:MinHeapDeltaBytes=1048576 -XX:NumberOfGCLogFiles=5 -XX:+PrintGC -XX:+PrintGCDateStamps -XX:-PrintGCDetails -XX:+PrintGCTimeStamps -XX:-PrintTenuringDistribution -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:+UseG1GC -XX:+UseGCLogFileRotation Command line: -Djava.util.logging.config.file=/usr/local/confluence-6.0.3/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE=32768 -Xms1536m -Xmx2048m -XX:+UseG1GC -Datlassian.plugins.enable.wait=300 -Djava.awt.headless=true -XX:G1ReservePercent=20 -Xloggc:/usr/local/confluence-6.0.3/logs/gc-2017-10-15_16-08-58.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M -XX:-PrintGCDetails -XX:+PrintGCDateStamps -XX:-PrintTenuringDistribution -Dhttp.socket.timeout=10 -Djava.endorsed.dirs=/usr/local/confluence-6.0.3/endorsed -Dcatalina.base=/usr/local/confluence-6.0.3 -Dcatalina.home=/usr/local/confluence-6.0.3 -Djava.io.tmpdir=/usr/local/confluence-6.0.3/temp 获取应用进程的命令行参数信息
[root@localhost ~]# jinfo -flags 3126
Attaching to process ID 3126, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.121-b13
Non-default VM flags: -XX:CICompilerCount=3 -XX:ConcGCThreads=1 -XX:G1HeapRegionSize=1048576 -XX:G1ReservePercent=20 -XX:GCLogFileSize=2097152 -XX:InitialHeapSize=1610612736 -XX:MarkStackSize=4194304 -XX:MaxHeapSize=2147483648 -XX:MaxNewSize=1287651328 -XX:MinHeapDeltaBytes=1048576 -XX:NumberOfGCLogFiles=5 -XX:+PrintGC -XX:+PrintGCDateStamps -XX:-PrintGCDetails -XX:+PrintGCTimeStamps -XX:-PrintTenuringDistribution -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:+UseG1GC -XX:+UseGCLogFileRotation
Command line: -Djava.util.logging.config.file=/usr/local/confluence-6.0.3/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE=32768 -Xms1536m -Xmx2048m -XX:+UseG1GC -Datlassian.plugins.enable.wait=300 -Djava.awt.headless=true -XX:G1ReservePercent=20 -Xloggc:/usr/local/confluence-6.0.3/logs/gc-2017-10-15_16-08-58.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M -XX:-PrintGCDetails -XX:+PrintGCDateStamps -XX:-PrintTenuringDistribution -Dhttp.socket.timeout=10 -Djava.endorsed.dirs=/usr/local/confluence-6.0.3/endorsed -Dcatalina.base=/usr/local/confluence-6.0.3 -Dcatalina.home=/usr/local/confluence-6.0.3 -Djava.io.tmpdir=/usr/local/confluence-6.0.3/temp [root@localhost ~]# [root@localhost ~]# jinfo -flag PrintGCDetails 3126 -XX:-PrintGCDetails [root@localhost ~]# jinfo -flag MaxHeapSize 3126 -XX:MaxHeapSize=2147483648 打印应用进程的系统参数信息(System.getProperties())
[root@localhost ~]# jinfo -sysprops 3126
Attaching to process ID 3126, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.121-b13
java.vendor = Oracle Corporation
sun.java.launcher = SUN_STANDARD
catalina.base = /usr/local/confluence-6.0.3
sun.management.compiler = HotSpot 64-Bit Tiered Compilers
catalina.useNaming = true
os.name = Linux
java.util.logging.config.file = /usr/local/confluence-6.0.3/conf/logging.properties sun.boot.class.path = /usr/local/jdk1.8.0_121/jre/lib/resources.jar:/usr/local/jdk1.8.0_121/jre/lib/rt.jar:/usr/local/jdk1.8.0_121/jre/lib/sunrsasign.jar:/usr/local/jdk1.8.0_121/jre/lib/jsse.jar:/usr/local/jdk1.8.0_121/jre/lib/jce.jar:/usr/local/jdk1.8.0_121/jre/lib/charsets.jar:/usr/local/jdk1.8.0_121/jre/lib/jfr.jar:/usr/local/jdk1.8.0_121/jre/classes java.vm.specification.vendor = Oracle Corporation java.runtime.version = 1.8.0_121-b13 atlassian.plugins.enable.wait = 300 user.name = root shared.loader = tomcat.util.scan.StandardJarScanFilter.jarsToScan = log4j-web*.jar,log4j-taglib*.jar,log4javascript*.jar,slf4j-taglib*.jar com.sun.jndi.ldap.connect.pool.protocol = plain ssl com.sun.jndi.ldap.connect.pool.authentication = simple tomcat.util.buf.StringCache.byte.enabled = true user.language = zh java.naming.factory.initial = org.apache.naming.java.javaURLContextFactory sun.boot.library.path = /usr/local/jdk1.8.0_121/jre/lib/amd64 atlassian.enable.spring.strong.cache.bean.metadata = true jdk.tls.ephemeralDHKeySize = 2048 java.version = 1.8.0_121 java.util.logging.manager = org.apache.juli.ClassLoaderLogManager user.timezone = Asia/Shanghai sun.arch.data.model = 64 atlassian.enable.spring.strong.cache.bean.metadata.flush = true java.endorsed.dirs = /usr/local/confluence-6.0.3/endorsed sun.cpu.isalist = sun.jnu.encoding = UTF-8 file.encoding.pkg = sun.io org.apache.tomcat.websocket.DEFAULT_BUFFER_SIZE = 32768 package.access = sun.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.tomcat. file.separator = / java.specification.name = Java Platform API Specification java.class.version = 52.0 user.country = CN java.home = /usr/local/jdk1.8.0_121/jre atlassian.org.osgi.framework.bootdelegation.extra = org.apache.lucene.* java.vm.info = mixed mode os.version = 3.10.0-514.6.1.el7.x86_64 com.sun.jndi.ldap.connect.pool.prefsize = 10 sun.font.fontmanager = sun.awt.X11FontManager path.separator = : java.vm.version = 25.121-b13 java.protocol.handler.pkgs = org.apache.catalina.webresources java.awt.printerjob = sun.print.PSPrinterJob sun.io.unicode.encoding = UnicodeLittle sun.java2d.opengl = true awt.toolkit = sun.awt.X11.XToolkit package.definition = sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.naming.,org.apache.tomcat. java.naming.factory.url.pkgs = org.apache.naming user.home = /root java.specification.vendor = Oracle Corporation tomcat.util.scan.StandardJarScanFilter.jarsToSkip = bootstrap.jar,commons-daemon.jar,tomcat-juli.jar,annotations-api.jar,el-api.jar,jsp-api.jar,servlet-api.jar,websocket-api.jar,catalina.jar,catalina-ant.jar,catalina-ha.jar,catalina-storeconfig.jar,catalina-tribes.jar,jasper.jar,jasper-el.jar,ecj-*.jar,tomcat-api.jar,tomcat-util.jar,tomcat-util-scan.jar,tomcat-coyote.jar,tomcat-dbcp.jar,tomcat-jni.jar,tomcat-websocket.jar,tomcat-i18n-en.jar,tomcat-i18n-es.jar,tomcat-i18n-fr.jar,tomcat-i18n-ja.jar,tomcat-juli-adapters.jar,catalina-jmx-remote.jar,catalina-ws.jar,tomcat-jdbc.jar,tools.jar,commons-beanutils*.jar,commons-codec*.jar,commons-collections*.jar,commons-dbcp*.jar,commons-digester*.jar,commons-fileupload*.jar,commons-httpclient*.jar,commons-io*.jar,commons-lang*.jar,commons-logging*.jar,commons-math*.jar,commons-pool*.jar,jstl.jar,taglibs-standard-spec-*.jar,geronimo-spec-jaxrpc*.jar,wsdl4j*.jar,ant.jar,ant-junit*.jar,aspectj*.jar,jmx.jar,h2*.jar,hibernate*.jar,httpclient*.jar,jmx-tools.jar,jta*.jar,log4j*.jar,mail*.jar,slf4j*.jar,xercesImpl.jar,xmlParserAPIs.jar,xml-apis.jar,junit.jar,junit-*.jar,ant-launcher.jar,cobertura-*.jar,asm-*.jar,dom4j-*.jar,icu4j-*.jar,jaxen-*.jar,jdom-*.jar,jetty-*.jar,oro-*.jar,servlet-api-*.jar,tagsoup-*.jar,xmlParserAPIs-*.jar,xom-*.jar java.library.path = /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib java.vendor.url = http://java.oracle.com/ java.vm.vendor = Oracle Corporation common.loader = "${catalina.base}/lib","${catalina.base}/lib/*.jar","${catalina.home}/lib","${catalina.home}/lib/*.jar" java.runtime.name = Java(TM) SE Runtime Environment sun.java.command = org.apache.catalina.startup.Bootstrap start java.class.path = /usr/local/confluence-6.0.3/bin/bootstrap.jar:/usr/local/confluence-6.0.3/bin/tomcat-juli.jar hibernate.bytecode.use_reflection_optimizer = true com.sun.jndi.ldap.connect.pool.maxsize = 0 java.vm.specification.name = Java Virtual Machine Specification java.vm.specification.version = 1.8 catalina.home = /usr/local/confluence-6.0.3 sun.cpu.endian = little sun.os.patch.level = unknown java.awt.headless = true java.io.tmpdir = /usr/local/confluence-6.0.3/temp java.vendor.url.bug = http://bugreport.sun.com/bugreport/ server.loader = os.arch = amd64 java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment java.ext.dirs = /usr/local/jdk1.8.0_121/jre/lib/ext:/usr/java/packages/lib/ext user.dir = / com.sun.jndi.ldap.connect.pool.initsize = 1 line.separator = java.vm.name = Java HotSpot(TM) 64-Bit Server VM file.encoding = UTF-8 com.sun.jndi.ldap.connect.pool.timeout = 30000 http.socket.timeout = 10 java.specification.version = 1.8 plugin.webresource.javascript.try.catch.wrapping = true 命令行工具-javap
javap是jdk自带的一个工具,可以对代码反编译,也可以查看java编译器生成的字节码.
javap语法
[root@localhost ~]# javap -help
用法: javap <options> <classes>
其中, 可能的选项包括:
-help --help -? 输出此用法消息
-version 版本信息
-v -verbose 输出附加信息
-l 输出行号和本地变量表
-public 仅显示公共类和成员
-protected 显示受保护的/公共类和成员
-package 显示程序包/受保护的/公共类
和成员 (默认)
-p -private 显示所有类和成员
-c 对代码进行反汇编
-s 输出内部类型签名
-sysinfo 显示正在处理的类的
系统信息 (路径, 大小, 日期, MD5 散列)
-constants 显示最终常量
-classpath <path> 指定查找用户类文件的位置
-cp <path> 指定查找用户类文件的位置
-bootclasspath <path> 覆盖引导类文件的位置
javap示例
javap命令分解一个class文件,它根据options来决定到底输出什么.如果没有使用options,那么javap将会输出包,类里的protected和public域以及类里的所有方法.javap将会把它们输出在标准输出上
示例代码
[root@localhost ~]# cat ThreadDumpTest.java
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ThreadDumpTest { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(3); for(int i=0; i<5; i++){ executor.submit(new ThreadPrint("测试线程"+ i)); } } static class ThreadPrint implements Runnable{ private String name; private ThreadPrint(String name){ this.name = name; } @Override public void run() { Thread thread = Thread.currentThread(); thread.setName(name); int i=0; while (true){ System.out.println(thread.getName() + "输出" + i++); } } } } [root@localhost ~]# javac ThreadDumpTest.java javap
[root@localhost ~]# javap ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
public static void main(java.lang.String[]);
}
-version
[root@localhost ~]# javap -version ThreadDumpTest.class
1.8.0_121
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
public static void main(java.lang.String[]);
}
-sysinfo
[root@localhost ~]# javap -sysinfo ThreadDumpTest.class
Classfile /root/ThreadDumpTest.class
Last modified 2017-10-15; size 967 bytes
MD5 checksum b8dce8aa07d62201b068e47eef31fa75
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
public static void main(java.lang.String[]);
}
-constants
[root@localhost ~]# javap -constants ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
public static void main(java.lang.String[]);
}
-l
[root@localhost ~]# javap -l ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
LineNumberTable:
line 4: 0
public static void main(java.lang.String[]);
LineNumberTable:
line 8: 0
line 9: 5
line 10: 12
line 9: 46
line 12: 52
}
-c
[root@localhost ~]# javap -c ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: iconst_3
1: invokestatic #2 // Method java/util/concurrent/Executors.newFixedThreadPool:(I)Ljava/util/concurrent/ExecutorService; 4: astore_1 5: iconst_0 6: istore_2 7: iload_2 8: iconst_5 9: if_icmpge 52 12: aload_1 13: new #3 // class ThreadDumpTest$ThreadPrint 16: dup 17: new #4 // class java/lang/StringBuilder 20: dup 21: invokespecial #5 // Method java/lang/StringBuilder."<init>":()V 24: ldc #6 // String 测试线程 26: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 29: iload_2 30: invokevirtual #8 // Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder; 33: invokevirtual #9 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 36: aconst_null 37: invokespecial #10 // Method ThreadDumpTest$ThreadPrint."<init>":(Ljava/lang/String;LThreadDumpTest$1;)V 40: invokeinterface #11, 2 // InterfaceMethod java/util/concurrent/ExecutorService.submit:(Ljava/lang/Runnable;)Ljava/util/concurrent/Future; 45: pop 46: iinc 2, 1 49: goto 7 52: return } -s
[root@localhost ~]# javap -s ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
descriptor: ()V
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
}
-package & -public & -protected & -private
[root@localhost ~]# javap -package ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
public static void main(java.lang.String[]);
}
[root@localhost ~]# javap -public ThreadDumpTest.class
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest {
public ThreadDumpTest();
public static void main(java.lang.String[]);
}
[root@localhost ~]# javap -protected ThreadDumpTest.class Compiled from "ThreadDumpTest.java" public class ThreadDumpTest { public ThreadDumpTest(); public static void main(java.lang.String[]); } [root@localhost ~]# javap -private ThreadDumpTest.class Compiled from "ThreadDumpTest.java" public class ThreadDumpTest { public ThreadDumpTest(); public static void main(java.lang.String[]); } -v
[root@localhost ~]# javap -v ThreadDumpTest.class
Classfile /root/ThreadDumpTest.class
Last modified 2017-10-15; size 967 bytes
MD5 checksum b8dce8aa07d62201b068e47eef31fa75
Compiled from "ThreadDumpTest.java"
public class ThreadDumpTest
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #13.#27 // java/lang/Object."<init>":()V
#2 = Methodref #28.#29 // java/util/concurrent/Executors.newFixedThreadPool:(I)Ljava/util/concurrent/ExecutorService;
#3 = Class #30 // ThreadDumpTest$ThreadPrint #4 = Class #31 // java/lang/StringBuilder #5 = Methodref #4.#27 // java/lang/StringBuilder."<init>":()V #6 = String #32 // 测试线程 #7 = Methodref #4.#33 // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; #8 = Methodref #4.#34 // java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder; #9 = Methodref #4.#35 // java/lang/StringBuilder.toString:()Ljava/lang/String; #10 = Methodref #3.#36 // ThreadDumpTest$ThreadPrint."<init>":(Ljava/lang/String;LThreadDumpTest$1;)V #11 = InterfaceMethodref #37.#38 // java/util/concurrent/ExecutorService.submit:(Ljava/lang/Runnable;)Ljava/util/concurrent/Future; #12 = Class #39 // ThreadDumpTest #13 = Class #40 // java/lang/Object #14 = Class #41 // ThreadDumpTest$1 #15 = Utf8 InnerClasses #16 = Utf8 ThreadPrint #17 = Utf8 <init> #18 = Utf8 ()V #19 = Utf8 Code #20 = Utf8 LineNumberTable #21 = Utf8 main #22 = Utf8 ([Ljava/lang/String;)V #23 = Utf8 StackMapTable #24 = Class #42 // java/util/concurrent/ExecutorService #25 = Utf8 SourceFile #26 = Utf8 ThreadDumpTest.java #27 = NameAndType #17:#18 // "<init>":()V #28 = Class #43 // java/util/concurrent/Executors #29 = NameAndType #44:#45 // newFixedThreadPool:(I)Ljava/util/concurrent/ExecutorService; #30 = Utf8 ThreadDumpTest$ThreadPrint #31 = Utf8 java/lang/StringBuilder #32 = Utf8 测试线程 #33 = NameAndType #46:#47 // append:(Ljava/lang/String;)Ljava/lang/StringBuilder; #34 = NameAndType #46:#48 // append:(I)Ljava/lang/StringBuilder; #35 = NameAndType #49:#50 // toString:()Ljava/lang/String; #36 = NameAndType #17:#51 // "<init>":(Ljava/lang/String;LThreadDumpTest$1;)V #37 = Class #42 // java/util/concurrent/ExecutorService #38 = NameAndType #52:#53 // submit:(Ljava/lang/Runnable;)Ljava/util/concurrent/Future; #39 = Utf8 ThreadDumpTest #40 = Utf8 java/lang/Object #41 = Utf8 ThreadDumpTest$1 #42 = Utf8 java/util/concurrent/ExecutorService #43 = Utf8 java/util/concurrent/Executors #44 = Utf8 newFixedThreadPool #45 = Utf8 (I)Ljava/util/concurrent/ExecutorService; #46 = Utf8 append #47 = Utf8 (Ljava/lang/String;)Ljava/lang/StringBuilder; #48 = Utf8 (I)Ljava/lang/StringBuilder; #49 = Utf8 toString #50 = Utf8 ()Ljava/lang/String; #51 = Utf8 (Ljava/lang/String;LThreadDumpTest$1;)V #52 = Utf8 submit #53 = Utf8 (Ljava/lang/Runnable;)Ljava/util/concurrent/Future; { public ThreadDumpTest(); descriptor: ()V flags: ACC_PUBLIC Code: stack=1, locals=1, args_size=1 0: aload_0 1: invokespecial #1 // Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 4: 0 public static void main(java.lang.String[]); descriptor: ([Ljava/lang/String;)V flags: ACC_PUBLIC, ACC_STATIC Code: stack=5, locals=3, args_size=1 0: iconst_3 1: invokestatic #2 // Method java/util/concurrent/Executors.newFixedThreadPool:(I)Ljava/util/concurrent/ExecutorService; 4: astore_1 5: iconst_0 6: istore_2 7: iload_2 8: iconst_5 9: if_icmpge 52 12: aload_1 13: new #3 // class ThreadDumpTest$ThreadPrint 16: dup 17: new #4 // class java/lang/StringBuilder 20: dup 21: invokespecial #5 // Method java/lang/StringBuilder."<init>":()V 24: ldc #6 // String 测试线程 26: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 29: iload_2 30: invokevirtual #8 // Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder; 33: invokevirtual #9 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 36: aconst_null 37: invokespecial #10 // Method ThreadDumpTest$ThreadPrint."<init>":(Ljava/lang/String;LThreadDumpTest$1;)V 40: invokeinterface #11, 2 // InterfaceMethod java/util/concurrent/ExecutorService.submit:(Ljava/lang/Runnable;)Ljava/util/concurrent/Future; 45: pop 46: iinc 2, 1 49: goto 7 52: return LineNumberTable: line 8: 0 line 9: 5 line 10: 12 line 9: 46 line 12: 52 StackMapTable: number_of_entries = 2 frame_type = 253 /* append */ offset_delta = 7 locals = [ class java/util/concurrent/ExecutorService, int ] frame_type = 250 /* chop */ offset_delta = 44 } SourceFile: "ThreadDumpTest.java" InnerClasses: static #14; //class ThreadDumpTest$1 static #16= #3 of #12; //ThreadPrint=class ThreadDumpTest$ThreadPrint of class ThreadDumpTest 命令行工具-jstat
jstat(JVM Statistics Monitoring Tool) 是用于监视虚拟机各种运行状态信息的命令行工具.它尅显示本地或者远程虚拟机进程中的类装载、内存、垃圾收集、JIT编译等运行数据.
jstat语法
[root@localhost ~]# jstat -help
Usage: jstat -help|-options
jstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]]
Definitions:
<option> An option reported by the -options option
<vmid> Virtual Machine Identifier. A vmid takes the following form:
<lvmid>[@<hostname>[:<port>]]
Where <lvmid> is the local vm identifier for the target
Java virtual machine, typically a process id; <hostname> is
the name of the host running the target Java virtual machine;
and <port> is the port number for the rmiregistry on the target host. See the jvmstat documentation for a more complete description of the Virtual Machine Identifier. <lines> Number of samples between header lines. <interval> Sampling interval. The following forms are allowed: <n>["ms"|"s"] Where <n> is an integer and the suffix specifies the units as milliseconds("ms") or seconds("s"). The default units are "ms". <count> Number of samples to take before terminating. -J<flag> Pass <flag> directly to the runtime system. [root@localhost ~]# jstat -options -class -compiler -gc -gccapacity -gccause -gcmetacapacity -gcnew -gcnewcapacity -gcold -gcoldcapacity -gcutil -printcompilation 参数说明
- -class : 监视类装载、卸载数量、总空间以及类装载所耗费的时间.
- -compiler : 显示编译器编译过的方法、耗时等信息.
- -gc : 显示Java堆状况、包括Eden区、两个survivor区、老年代、永久代等的容量、已用空间、GC次数以及时间等信息.
- -gccapacity: 显示VM内存中三代(young,old,perm）对象的使用和占用大小
- -gcutil : gc统计信息, 输出主要关注已使用空间占总弓箭的百分比
- -gccause : 与-gcutil基本相同, 会额外输出导致上一次GC产生的原因
- -gcnew : 显示新生代GC状况
- -gcnewcapacity : 显示内容与-gcnew相同,输出主要关注使用到的最大最小空间
- -gcold : 显示老年代GC状况
- -gcoldcapacity : 显示内容与-gcold相同,输出主要关注使用到的最大最小空间
- -printcompilation : 当前vm执行的信息
jstat示例说明
每2s执行一次查询统计,执行5次gc统计输出
[root@localhost ~]# jstat -gc 3126 2 5
S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT
0.0 81920.0 0.0 81920.0 566272.0 136192.0 924672.0 558080.0 224076.0 205898.7 31368.0 26476.7 36 2.526 0 0.000 2.526
0.0 81920.0 0.0 81920.0 566272.0 136192.0 924672.0 558080.0 224076.0 205898.7 31368.0 26476.7 36 2.526 0 0.000 2.526
0.0 81920.0 0.0 81920.0 566272.0 136192.0 924672.0 558080.0 224076.0 205898.7 31368.0 26476.7 36 2.526 0 0.000 2.526
0.0 81920.0 0.0 81920.0 566272.0 136192.0 924672.0 558080.0 224076.0 205898.7 31368.0 26476.7 36 2.526 0 0.000 2.526
0.0 81920.0 0.0 81920.0 566272.0 136192.0 924672.0 558080.0 224076.0 205898.7 31368.0 26476.7 36 2.526 0 0.000 2.526
-class
[root@localhost ~]# jstat -class 3126
Loaded Bytes Unloaded Bytes Time
39652 72532.0 15 70.1 76.55
-compiler
[root@localhost ~]# jstat -compiler 3126
Compiled Failed Invalid Time FailedType FailedMethod
28416 5 0 155.87 1 com/mysql/jdbc/AbandonedConnectionCleanupThread run
-gc
[root@localhost ~]# jstat -gc 3126
S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT
0.0 87040.0 0.0 87040.0 601088.0 286720.0 884736.0 513536.0 223820.0 205799.4 31368.0 26473.9 35 2.374 0 0.000 2.374
-gccapacity
[root@localhost ~]# jstat -gccapacity 3126
NGCMN NGCMX NGC S0C S1C EC OGCMN OGCMX OGC OC MCMN MCMX MC CCSMN CCSMX CCSC YGC FGC
0.0 2097152.0 688128.0 0.0 87040.0 601088.0 0.0 2097152.0 884736.0 884736.0 0.0 1241088.0 223820.0 0.0 1048576.0 31368.0 35 0
-gcutil & -gccause
[root@localhost ~]# jstat -gcutil 3126
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT
0.00 100.00 40.03 58.04 91.95 84.40 35 2.374 0 0.000 2.374
[root@localhost ~]# jstat -gccause 3126
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT LGCC GCC
0.00 100.00 40.03 58.04 91.95 84.40 35 2.374 0 0.000 2.374 G1 Evacuation Pause No GC
参数说明
- S0: 新生代中Survivor space 0区已使用空间的百分比
- S1: 新生代中Survivor space 1区已使用空间的百分比
- E: 新生代已使用空间的百分比
- O: 老年代已使用空间的百分比
- P: 永久带已使用空间的百分比
- YGC: 从应用程序启动到当前，发生Yang GC 的次数
- YGCT: 从应用程序启动到当前，Yang GC所用的时间【单位秒】
- FGC: 从应用程序启动到当前，发生Full GC的次数
- FGCT: 从应用程序启动到当前，Full GC所用的时间
- GCT: 从应用程序启动到当前，用于垃圾回收的总时间【单位秒】
-gcmetacapacity
[root@localhost ~]# jstat -gcmetacapacity 3126
MCMN MCMX MC CCSMN CCSMX CCSC YGC FGC FGCT GCT
0.0 1241088.0 223820.0 0.0 1048576.0 31368.0 35 0 0.000 2.374
-gcnew & -gcnewcapacity
[root@localhost ~]# jstat -gcnew 3126
S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
0.0 87040.0 0.0 87040.0 15 15 43520.0 601088.0 354304.0 35 2.374
[root@localhost ~]# jstat -gcnewcapacity 3126
NGCMN NGCMX NGC S0CMX S0C S1CMX S1C ECMX EC YGC FGC
0.0 2097152.0 688128.0 0.0 0.0 2097152.0 87040.0 2097152.0 601088.0 35 0
-gcold & -gcoldcapacity
[root@localhost ~]# jstat -gcold 3126
MC MU CCSC CCSU OC OU YGC FGC FGCT GCT
223820.0 205799.4 31368.0 26473.9 884736.0 513536.0 35 0 0.000 2.374
[root@localhost ~]# jstat -gcoldcapacity 3126
OGCMN OGCMX OGC OC YGC FGC FGCT GCT
0.0 2097152.0 884736.0 884736.0 35 0 0.000 2.374
-printcompilation
[root@localhost ~]# jstat -printcompilation 3126
Compiled Size Type Method
28485 305 1 java/util/GregorianCalendar pinDayOfMonth
[root@localhost ~]# jstat -printcompilation 3126
Compiled Size Type Method
28486 362 1 java/lang/StringCoding encode
命令行工具-jstack
jstack(Stack Trace for Java) 命令用于生成虚拟机当前时刻的线程快照(一般称为threaddump或者javacore文件), 线程快照就是当前虚拟机内每一条线程正在执行的方法堆栈的集合,生成线程快照的主要目的是定位线程出现长时间停顿的原因，如线程间死锁、死循环、请求外部资源导致的长时间等待等.
在实际运行中，往往一次 dump的信息，还不足以确认问题。建议产生三次 dump信息，如果每次 dump都指向同一个问题，我们才确定问题的典型性。
jstack语法
[root@localhost ~]# jstack -help
Usage:
jstack [-l] <pid>
(to connect to running process)
jstack -F [-m] [-l] <pid>
(to connect to a hung process)
jstack [-m] [-l] <executable> <core>
(to connect to a core file)
jstack [-m] [-l] [server_id@]<remote server IP or hostname>
(to connect to a remote debug server)
Options:
-F to force a thread dump. Use when jstack <pid> does not respond (process is hung)
-m to print both java and native frames (mixed mode)
-l long listing. Prints additional information about locks
-h or -help to print this help message 参数说明
- _F : 当正常输出的请求不被响应时,强制输出线程堆栈
- -l : 长列表,打印关于锁的附加信息
- -m : 打印java和native方法(c/c++)的堆栈信息
jstack示例
使用jstack查看线程堆栈
[root@localhost ~]# jstack -l 3126
2017-10-15 20:16:00
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.121-b13 mixed mode):
"Attach Listener" #171 daemon prio=9 os_prio=0 tid=0x00007feab0561800 nid=0x10d4 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"lucene-tracked-searchers-pruner-pool-19-thread-1" #170 prio=5 os_prio=0 tid=0x00007feac483d000 nid=0xdb9 waiting on condition [0x00007fea64670000] java.lang.Thread.State: TIMED_WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000009794bb68> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None "SupportHealthCheckThread-8" #169 daemon prio=5 os_prio=0 tid=0x00007feaa03cc800 nid=0xdb8 waiting on condition [0x00007fea63b65000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000008dc7bc18> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None 使用jstack分析问题代码
示例展示使用Jstack查看CPU导致CPU使用率过高的问题代码
查看CPU使用率比较高的进程
[root@localhost ~]# top
top - 21:06:30 up 4:58, 3 users, load average: 0.59, 0.17, 0.09
Tasks: 185 total, 3 running, 182 sleeping, 0 stopped, 0 zombie
%Cpu(s): 11.7 us, 27.6 sy, 0.0 ni, 60.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 7874196 total, 6227236 free, 855436 used, 791524 buff/cache
KiB Swap: 8126460 total, 8126460 free, 0 used. 6712744 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13176 root 20 0 4643776 60552 11976 S 83.3 0.8 0:14.11 java
13047 root 20 0 151508 6856 3972 R 77.8 0.1 0:52.33 sshd
320 root 20 0 0 0 0 S 38.9 0.0 0:01.67 kworker/1:2
792 root 20 0 4368 588 496 S 5.6 0.0 0:02.37 rngd
13202 root 20 0 157708 2300 1564 R 5.6 0.0 0:00.11 top
1 root 20 0 128092 6700 3948 S 0.0 0.1 0:01.97 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 0:00.02 ksoftirqd/0
5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H
7 root rt 0 0 0 0 S 0.0 0.0 0:00.01 migration/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
9 root 20 0 0 0 0 S 0.0 0.0 0:13.28 rcu_sched
10 root rt 0 0 0 0 S 0.0 0.0 0:00.08 watchdog/0
11 root rt 0 0 0 0 S 0.0 0.0 0:00.08 watchdog/1
12 root rt 0 0 0 0 S 0.0 0.0 0:00.02 migration/1
13 root 20 0 0 0 0 S 0.0 0.0 0:00.10 ksoftirqd/1
15 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/1:0H
16 root rt 0 0 0 0 S 0.0 0.0 0:00.08 watchdog/2
17 root rt 0 0 0 0 S 0.0 0.0 0:00.01 migration/2
18 root 20 0 0 0 0 S 0.0 0.0 0:00.16 ksoftirqd/2
20 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/2:0H
21 root rt 0 0 0 0 S 0.0 0.0 0:00.08 watchdog/3
22 root rt 0 0 0 0 S 0.0 0.0 0:00.01 migration/3
23 root 20 0 0 0 0 S 0.0 0.0 0:00.14 ksoftirqd/3
25 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/3:0H
27 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 khelper
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdevtmpfs
29 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 netns
30 root 20 0 0 0 0 S 0.0 0.0 0:00.01 khungtaskd
31 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 writeback
32 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kintegrityd
33 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset
34 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kblockd
[root@localhost ~]# jps -lv
13176 ThreadDumpTest
13230 sun.tools.jps.Jps -Dapplication.home=/usr/local/jdk1.8.0_121 -Xms8m
上面可以看到CPU使用率比较高的进程为13176, 可以定位CPU使用率过高的进程主类为ThreadDumpTest
查看进程内使用率比较高的线程
[root@localhost ~]# top Hp 13176
top - 21:11:05 up 5:02, 3 users, load average: 0.92, 0.49, 0.23
Threads: 19 total, 2 running, 17 sleeping, 0 stopped, 0 zombie
%Cpu(s): 10.6 us, 26.7 sy, 0.0 ni, 62.6 id, 0.0 wa, 0.0 hi, 0.1 si, 0.0 st
KiB Mem : 7874196 total, 6228368 free, 854004 used, 791824 buff/cache
KiB Swap: 8126460 total, 8126460 free, 0 used. 6713884 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13193 root 20 0 4710340 61008 11976 R 34.7 0.8 0:16.40 java
13191 root 20 0 4710340 61008 11976 R 27.3 0.8 0:20.71 java
13192 root 20 0 4710340 61008 11976 S 14.0 0.8 0:19.79 java
13176 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.00 java
13177 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.04 java
13178 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.01 java
13179 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.02 java
13180 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.02 java
13181 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.02 java
13182 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.01 java
13183 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.00 java
13184 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.00 java
13185 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.00 java
13186 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.13 java
13187 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.10 java
13188 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.02 java
13189 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.00 java
13190 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.03 java
13290 root 20 0 4710340 61008 11976 S 0.0 0.8 0:00.00 java
图中可以看到进程13176中线程13197使用CPU率最高(13191、13192其次)
将线程号(十进制)转换后的16进制
[root@localhost ~]# printf "%x\n" 13193
3389
[root@localhost ~]# printf "%x\n" 13191
3387
[root@localhost ~]# printf "%x\n" 13192
3388
输出线程堆栈信息
[root@localhost ~]# jstack -l 13176
2017-10-15 21:11:23
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.121-b13 mixed mode):
"Attach Listener" #13 daemon prio=9 os_prio=0 tid=0x00007f94ac001000 nid=0x33ea waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"DestroyJavaVM" #12 prio=5 os_prio=0 tid=0x00007f94ec008800 nid=0x3379 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "测试线程2" #11 prio=5 os_prio=0 tid=0x00007f94ec0f8800 nid=0x3389 waiting for monitor entry [0x00007f94cf3f2000] java.lang.Thread.State: BLOCKED (on object monitor) at java.io.PrintStream.println(PrintStream.java:805) - waiting to lock <0x0000000087c06a90> (a java.io.PrintStream) at ThreadDumpTest$ThreadPrint.run(ThreadDumpTest.java:28) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x0000000087c06c30> (a java.util.concurrent.ThreadPoolExecutor$Worker) "测试线程1" #10 prio=5 os_prio=0 tid=0x00007f94ec0f7000 nid=0x3388 waiting for monitor entry [0x00007f94cf4f3000] java.lang.Thread.State: BLOCKED (on object monitor) at java.io.PrintStream.println(PrintStream.java:805) - waiting to lock <0x0000000087c06a90> (a java.io.PrintStream) at ThreadDumpTest$ThreadPrint.run(ThreadDumpTest.java:28) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x0000000087c06f98> (a java.util.concurrent.ThreadPoolExecutor$Worker) "测试线程0" #9 prio=5 os_prio=0 tid=0x00007f94ec0f5000 nid=0x3387 runnable [0x00007f94cf5f4000] java.lang.Thread.State: RUNNABLE at java.io.FileOutputStream.writeBytes(Native Method) at java.io.FileOutputStream.write(FileOutputStream.java:326) at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82) at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140) - locked <0x0000000087c21ca0> (a java.io.BufferedOutputStream) at java.io.PrintStream.write(PrintStream.java:482) - locked <0x0000000087c06a90> (a java.io.PrintStream) at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221) at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291) at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:104) - locked <0x0000000087c081a0> (a java.io.OutputStreamWriter) at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:185) at java.io.PrintStream.newLine(PrintStream.java:546) - eliminated <0x0000000087c06a90> (a java.io.PrintStream) at java.io.PrintStream.println(PrintStream.java:807) - locked <0x0000000087c06a90> (a java.io.PrintStream) at ThreadDumpTest$ThreadPrint.run(ThreadDumpTest.java:28) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x0000000087c0e1c0> (a java.util.concurrent.ThreadPoolExecutor$Worker) "Service Thread" #8 daemon prio=9 os_prio=0 tid=0x00007f94ec0d9800 nid=0x3385 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C1 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007f94ec0bc000 nid=0x3384 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f94ec0ba800 nid=0x3383 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f94ec0b7800 nid=0x3382 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f94ec0b6000 nid=0x3381 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f94ec083000 nid=0x3380 in Object.wait() [0x00007f94cfcfb000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x0000000087c0e4e8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143) - locked <0x0000000087c0e4e8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209) Locked ownable synchronizers: - None "Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f94ec07e800 nid=0x337f in Object.wait() [0x00007f94cfdfc000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x0000000087c10768> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x0000000087c10768> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) Locked ownable synchronizers: - None "VM Thread" os_prio=0 tid=0x00007f94ec076800 nid=0x337e runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f94ec01d800 nid=0x337a runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f94ec01f800 nid=0x337b runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007f94ec021000 nid=0x337c runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007f94ec023000 nid=0x337d runnable "VM Periodic Task Thread" os_prio=0 tid=0x00007f94ec0dc800 nid=0x3386 waiting on condition JNI global references: 11 上面步骤中进程内高CPU线程对应的16进制分表为0x3389、0x3397、0x3388,
分析线程快照可以看到分别对应快照中的nid=0x3389、nid=0x3397、nid=0x3388线程,
发现问题代码ThreadDumpTest$ThreadPrint.run(ThreadDumpTest.java:28)
定位问题代码
上面高CPU线程指向的问题代码如下:
"测试线程2" #11 prio=5 os_prio=0 tid=0x00007f94ec0f8800 nid=0x3389 waiting for monitor entry [0x00007f94cf3f2000]
java.lang.Thread.State: BLOCKED (on object monitor)
at java.io.PrintStream.println(PrintStream.java:805)
- waiting to lock <0x0000000087c06a90> (a java.io.PrintStream)
at ThreadDumpTest$ThreadPrint.run(ThreadDumpTest.java:28)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x0000000087c06c30> (a java.util.concurrent.ThreadPoolExecutor$Worker) 查看我们的问题示例代码
[root@localhost ~]# cat ThreadDumpTest.java -n
1 import java.util.concurrent.ExecutorService;
2 import java.util.concurrent.Executors; 3 4 public class ThreadDumpTest { 5 6 public static void main(String[] args) { 7 8 ExecutorService executor = Executors.newFixedThreadPool(3); 9 for(int i=0; i<5; i++){ 10 executor.submit(new ThreadPrint("测试线程"+ i)); 11 } 12 } 13 14 static class ThreadPrint implements Runnable{ 15 16 private String name; 17 18 private ThreadPrint(String name){ 19 this.name = name; 20 } 21 22 @Override 23 public void run() { 24 Thread thread = Thread.currentThread(); 25 thread.setName(name); 26 int i=0; 27 while (true){ 28 System.out.println(thread.getName() + "输出" + i++); 29 } 30 } 31 } 32 33 } [root@localhost ~]# 死循环输出导致CPU使用率过高.
说明
虚拟机执行Full GC时,会阻塞所有的用户线程。因此,即时获取到同步锁的线程也有可能被阻塞。 在查看线程Dump时,首先查看内存使用情况。
线程状态
通过jstack命令查看线程堆栈信息时可能会看到的线程的几种状态
- NEW : 未启动的。不会出现在Dump中。
- RUNNABLE : 在虚拟机内执行的。
- BLOCKED : 受阻塞并等待监视器锁。
- WATING : 无限期等待另一个线程执行特定操作。
- TIMED_WATING : 有时限的等待另一个线程的特定操作。
- TERMINATED : 已退出的。
命令行工具-Jmap
jmap(Java Memory Map) 用户生成堆转储快照(HeapDump), jmap的作用不仅仅是为了获取HeapDump文件, 它还可以查询finalize执行队列、Java堆和永久待的详细信息, 如空间使用率、当前用的是哪种收集器等.
说明
HeapDump是反应Java堆使用情况的内存镜像;其中主要包括系统信息、虚拟机属性、完整的线程Dump、所有类和对象的状态等.
jmap语法
[root@localhost ~]# jmap -help
Usage:
jmap [option] <pid>
(to connect to running process)
jmap [option] <executable <core>
(to connect to a core file)
jmap [option] [server_id@]<remote server IP or hostname>
(to connect to remote debug server)
where <option> is one of:
<none> to print same info as Solaris pmap
-heap to print java heap summary
-histo[:live] to print histogram of java object heap; if the "live" suboption is specified, only count live objects -clstats to print class loader statistics -finalizerinfo to print information on objects awaiting finalization -dump:<dump-options> to dump java heap in hprof binary format dump-options: live dump only live objects; if not specified, all objects in the heap are dumped. format=b binary format file=<file> dump heap to <file> Example: jmap -dump:live,format=b,file=heap.bin <pid> -F force. Use with -dump:<dump-options> <pid> or -histo to force a heap dump or histogram when <pid> does not respond. The "live" suboption is not supported in this mode. -h | -help to print this help message -J<flag> to pass <flag> directly to the runtime system 参数说明
- -heap : 显示Java堆详细信息,如使用哪种回收机,参数配置,分代状况等.只在Linux/Solaris平台下有效
- -histo : 显示堆中对象统计信息, 包括类、示例梳理、合计容量
- -finalizerinfo : 打印等待终结的对象信息
- -dump : 以hprof二进制格式转储Java堆到指定filename的文件中,live子选项是可选的, 如果指定了live子选项,堆中只有活动的对象会被转储.想要浏览heap dump,你可以使用jhat(Java堆分析工具)读取生成的文件.
- -F : 强制模式.如果指定的pid没有响应,请使用jmap -dump或jmap -histo选项.
- -J<flag> : 指定传递给运行jmap的JVM的参数.
jmap示例
-heap
[root@localhost ~]# jmap -heap 15051
Attaching to process ID 15051, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.121-b13
using thread-local object allocation.
Parallel GC with 4 thread(s)
Heap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize = 2017460224 (1924.0MB)
NewSize = 42467328 (40.5MB)
MaxNewSize = 672137216 (641.0MB)
OldSize = 85458944 (81.5MB)
NewRatio = 2
SurvivorRatio = 8
MetaspaceSize = 21807104 (20.796875MB)
CompressedClassSpaceSize = 1073741824 (1024.0MB)
MaxMetaspaceSize = 17592186044415 MB
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 546832384 (521.5MB)
used = 111311816 (106.15522003173828MB)
free = 435520568 (415.3447799682617MB)
20.355746890074453% used
From Space:
capacity = 59768832 (57.0MB)
used = 40423064 (38.550437927246094MB)
free = 19345768 (18.449562072753906MB)
67.63234724078262% used
To Space:
capacity = 62390272 (59.5MB)
used = 0 (0.0MB)
free = 62390272 (59.5MB)
0.0% used
PS Old Generation
capacity = 170393600 (162.5MB)
used = 68197144 (65.0378646850586MB)
free = 102196456 (97.4621353149414MB)
40.02330134465144% used
31756 interned Strings occupying 3488392 bytes.
参数说明
-
Parallel GC with 4 thread(s): 说明使用的GC为Parallel GC
-
Heap Configuration: 堆内存初始化配置
- MinHeapFreeRatio: 对应jvm启动参数-XX:MinHeapFreeRatio设置JVM堆最小空闲比率(default 40)
- MaxHeapFreeRatio: 对应jvm启动参数 -XX:MaxHeapFreeRatio设置JVM堆最大空闲比率(default 70)
- MaxHeapSize: 对应jvm启动参数-XX:MaxHeapSize=设置JVM堆的最大大小
- NewSize: 对应jvm启动参数-XX:NewSize=设置JVM堆的‘新生代’的默认大小
- MaxNewSize: 对应jvm启动参数-XX:MaxNewSize=设置JVM堆的‘新生代’的最大大小
- OldSize: 对应jvm启动参数-XX:OldSize=<value>:设置JVM堆的‘老生代’的大小
- NewRatio: 对应jvm启动参数-XX:NewRatio=:‘新生代’和‘老生代’的大小比率
- SurvivorRatio: 对应jvm启动参数-XX:SurvivorRatio=设置年轻代中Eden区与Survivor区的大小比值
- PermSize: 对应jvm启动参数-XX:PermSize=<value>:设置JVM堆的‘永生代’的初始大小
- MaxPermSize: 对应jvm启动参数-XX:MaxPermSize=<value>:设置JVM堆的‘永生代’的最大大小
-
Heap Usage: 堆内存使用情况
- PS Young Generation: 当前的年轻代内存分布
- Eden Space: Eden区内存分布
- capacity: 区总容量
- used: 区已使用
- free: 区剩余容量
- From Space: 其中一个Survivor区的内存分布
- To Space: 另一个Survivor区的内存分布
- Eden Space: Eden区内存分布
- PS Old Generation: 当前的老年代内存分布
- PS Perm Generation: 当前的 “永生代” 内存分布
- PS Young Generation: 当前的年轻代内存分布
-histo
jmap -histo 输出堆中对象统计信息(示例截取部分输出)
[root@localhost ~]# jmap -histo 15051
num #instances #bytes class name
----------------------------------------------
1: 500577 126716152 [C
2: 26232 65237120 [B
3: 14504 35776824 [I
4: 383664 9207936 java.lang.String
5: 64455 5672040 java.lang.reflect.Method
6: 51405 4934880 java.util.jar.JarFile$JarFileEntry
7: 97535 3287848 [Ljava.lang.Object;
8: 98414 3149248 java.util.HashMap$Node
9: 72032 2305024 java.util.concurrent.ConcurrentHashMap$Node 10: 25440 1831680 java.lang.reflect.Field 11: 14102 1742584 [Ljava.util.HashMap$Node; 12: 68096 1489240 [Ljava.lang.Class; 13: 25091 1216184 [Ljava.lang.String; 14: 10460 1183000 java.lang.Class 15: 24437 1172976 org.aspectj.weaver.reflect.ShadowMatchImpl 16: 2040 1094240 [Ljava.util.concurrent.ConcurrentHashMap$Node; 17: 31998 1023936 org.apache.ibatis.reflection.property.PropertyTokenizer 18: 17825 998200 java.util.LinkedHashMap 19: 13505 864320 java.net.URL 20: 19868 794720 java.util.LinkedHashMap$Entry 21: 24437 781984 org.aspectj.weaver.patterns.ExposedState 22: 22626 724032 java.lang.ref.WeakReference 23: 14512 696576 java.nio.HeapByteBuffer 24: 14483 695184 java.nio.HeapCharBuffer 25: 21682 693824 java.util.Hashtable$Entry 26: 27121 650904 java.util.ArrayList 27: 26287 630888 java.lang.StringBuilder 28: 13050 626400 java.util.HashMap 29: 11340 453600 com.google.common.collect.AbstractMapBasedMultimap$WrappedSet 30: 11340 453600 com.google.common.collect.LinkedHashMultimap$ValueSet 31: 8848 424704 org.apache.catalina.loader.ResourceEntry 32: 10057 402280 java.util.TreeMap$Entry 33: 17013 400008 [Ljava.lang.reflect.Type; 34: 4850 388000 java.lang.reflect.Constructor 35: 11918 381376 java.lang.StackTraceElement 36: 1219 344448 [Ljava.util.Hashtable$Entry; 37: 3921 332080 [Ljava.lang.reflect.Method; 38: 8123 324920 java.lang.ref.Finalizer 39: 8047 321880 java.lang.ref.SoftReference 说明
jmap -histo:live 这个命令执行,JVM会先触发gc,然后再统计信息.
jmap -dump:format=b,file=heapDump 进程
这个命令执行,JVM会将整个heap的信息dump写入到一个文件,heap如果比较大的话,就会导致这个过程比较耗时,并且执行的过程中为了保证dump的信息是可靠的,所以会暂停应用.
[root@localhost ~]# jmap -dump:format=b,file=heapDump 15051
Dumping heap to /root/heapDump ...
Heap dump file created
[root@localhost ~]# jhat -port 8899 heapDump
Reading from heapDump...
Dump file created Sun Oct 15 23:10:28 CST 2017
Snapshot read, resolving...
Resolving 2737044 objects...
Chasing references, expect 547 dots...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Eliminating duplicate references...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Snapshot resolved.
Started HTTP server on port 8899
Server is ready.
浏览器访问: http://ip:8899/
jmap使用总结
- 如果程序内存不足或者频繁GC,很有可能存在内存泄露情况,这时候就要借助Java堆Dump查看对象的情况
- 要制作堆Dump可以直接使用jvm自带的jmap命令
- 使用jmap -histo:[live]查看堆内存中的对象的情况.如果有大量对象在持续被引用,并没有被释放掉,那就产生了内存泄露,就要结合代码,把不用的对象释放掉
- 用 jmap -dump:format=b,file=<fileName>命令将堆信息保存到一个文件中,再借助jhat命令查看详细内容
- 在内存出现泄露、溢出或者其它前提条件下,建议多dump几次内存,把内存文件进行编号归档,便于后续内存整理分析.
命令行工具-jhat
jhat(JVM Heap Analysis Tool) 命令与jmap搭配使用, 用来分析jmap生成的堆转储快照, jhat内置了一个微型的HTTP/HTML服务器, 方便在浏览器中查看jmap生成的HeadpDump文件.
jhat语法
[root@localhost ~]# jhat -help
Usage: jhat [-stack <bool>] [-refs <bool>] [-port <port>] [-baseline <file>] [-debug <int>] [-version] [-h|-help] <file>
-J<flag> Pass <flag> directly to the runtime system. For
example, -J-mx512m to use a maximum heap size of 512MB
-stack false: Turn off tracking object allocation call stack.
-refs false: Turn off tracking of references to objects
-port <port>: Set the port for the HTTP server. Defaults to 7000 -exclude <file>: Specify a file that lists data members that should be excluded from the reachableFrom query. -baseline <file>: Specify a baseline object dump. Objects in both heap dumps with the same ID and same class will be marked as not being "new". -debug <int>: Set debug level. 0: No debug output 1: Debug hprof file parsing 2: Debug hprof file parsing, no server -version Report version number -h|-help Print this help and exit <file> The file to read For a dump file that contains multiple heap dumps, you may specify which dump in the file by appending "#<number>" to the file name, i.e. "foo.hprof#3". All boolean options default to "true" 参数说明
- -stack : 关闭对象分配调用栈跟踪,如果分配位置信息在堆转储中不可用,则必须将此标志设置为false. 默认值为true.
- -refs : 关闭对象引用跟踪;默认值为true;默认情况下,返回的指针是指向其他特定对象的对象,如反向链接或输入引用,会统计/计算堆中的所有对象.
- -port : 设置jhat HTTP server 的端口号. 默认值7000.
- -exclude : 指定对象查询时需要排除的数据成员列表文件;例如:如果文件列列出了 java.lang.String.value,那么当从某个特定对象Object o计算可达的对象列表时,引用路径涉及 java.lang.String.value的都会被排除.
- -baseline : 指定一个基准堆转储;在两个heap dumps中有相同object ID的对象会被标记为不是新的,其他对象被标记为新的(new),在比较两个不同的堆转储时很有用.
- -debug : 设置debug 级别. 0表示不输出调试信息.
- -version :启动后只显示版本信息就退出
jhat示例
生成java堆转储文件,并用jhat分析
[root@localhost ~]# jmap -dump:format=b,file=heapDump 15051
Dumping heap to /root/heapDump ...
Heap dump file created
[root@localhost ~]# jhat -port 8899 heapDump
Reading from heapDump...
Dump file created Sun Oct 15 23:10:28 CST 2017
Snapshot read, resolving...
Resolving 2737044 objects...
Chasing references, expect 547 dots...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Eliminating duplicate references...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Snapshot resolved.
Started HTTP server on port 8899
Server is ready.
示例机器ip地址: 192.168.0.107, 所以只需要访问http://192.168.0.107:8899即可, 一般查看堆异常情况主要看这个两各部分
- 平台外的所有对象信息: Show instance counts for all classes (excluding platform)
- 以树状图形式展示堆情况: Show heap histogram
具体排查时需要结合代码,观察是否大量应该被回收的对象在一直被引用或者是否有占用内存特别大的对象无法被回收.
jhat对象查询
OQL语句的执行页面: http://ip:端口/oql/
OQL帮助信息页面为: http://ip:端口/oqlhelp/
参考文档
- 《深入理解Java虚拟机》
- http://docs.oracle.com/javase/7/docs/technotes/tools/share/jps.html
- http://docs.oracle.com/javase/7/docs/technotes/tools/share/jinfo.html
- http://www.hollischuang.com/archives/303
- http://docs.oracle.com/javase/7/docs/technotes/tools/share/jstat.html
- http://www.hollischuang.com/archives/481
- http://blog.csdn.net/fenglibing/article/details/6411951
- http://docs.oracle.com/javase/7/docs/technotes/tools/share/jstack.html
- http://www.hollischuang.com/archives/110
- http://www.hollischuang.com/archives/1047
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