查看JVM内存状态的工具使用

只是介绍SUN JDK自带的小工具

一些工具的链接http://docs.oracle.com/javase/1.5.0/docs/tooldocs/

jps -lvm
jinfo
jstat -options查看可用的选项http://docs.oracle.com/javase/1.5.0/docs/tooldocs/share/jstat.html
jstat -gc
jstat -gcutil    统计gc时，heap情况

jmap
jmap prints shared object memory maps or heap memory details of a given process or core file or a remote debug server.
used frequently
    jmap -heap:format=b <pid> to dump java heap in hprof binary format: heap.bin Dump出内存使用详情
    jmap -heap <pid>
jmap [ option ] pid
jmap [ option ] executable core
jmap [ option ] [server-id@]remote-hostname-or-IP    
    ?e.g.?(还不确定如何远程连接)    step 1. jsadebugd 6664 amrndhl235    step 2. jmap -heap 6664@amrndhl235
    rmiregistry -J-Xbootclasspath:$JAVA_HOME/lib/sa-jdi.jar
OPTIONS
    <no option>
        When no option is used jmap prints shared object mappings. For each shared object loaded in the target VM, start address, the size of the mapping, and the full path of the shared object file are printed. This is similar to the Solaris pmap utility.
    -heap
        Prints a heap summary. GC algorithm used, heap configuration and generation wise heap usage are printed.
    -histo
        Prints a histogram of the heap. For each Java class, number of objects, memory size in bytes, and fully qualified class names are printed. VM internal class names are printed with '*' prefix.
    -permstat
        Prints class loader wise statistics of permanent generation of Java heap. For each class loader, its name, liveness, address, parent class loader, and the number and size of classes it has loaded are printed.
    -h    Prints a help message.
        
jconsole监控 (用JMX监测JVM的运行参数)
   使用时需要在启动application时加入参数

    JAVA_OPTS="-Djava.rmi.server.hostname=amrndhl235 -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=5000 -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false"

如果需要设置密码要设置authenticate=true,并且设置密码文件

JAVA_OPTS="$JAVA_OPTS -Dcom.sun.management.jmxremote.access.file=/home/tomcat/jmxremote.access -Dcom.sun.management.jmxremote.password.file=/home/tomcat/jmxremote.password"

密码文件内容

# jmx remote authentication password entries
admin   password
support passwordSupport

在linux上需要设置它的权限chmod 600 jmxremote.password

jmxremote.access文件内容
# Access control entries:
admin   readwrite
support readonly

关于JMX，可以参考

Monitoring and Management Using JMX

用JMX管理你的JVM

    JConsole 运行对application是有开销的，例如：首先独自运行一个应用程序，然后在分析器下运行，并测量差异。比如JDK附带的demo SwingSet2.
    先使用java -verbose:gc -Xms10m -Xmx19m -Djava.rmi.server.hostname=AMRGROLL3DK364 -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=5000 -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false -jar SwingSet2.jar　运行 SwingSet2 来查看垃圾收集清理然后运行同一个应用程序并将 JConsole 分析器连接到它。当 JConsole 连接好了之后，一个稳定的 GC 清理流出现，否则不会出现。这就是分析器的性能开销。
   

JDK 6还带了jvisualvm (VisualVM 入门指南)
推荐安装visualvm的插件Tools->Plugins

安装后，插件位置看Help->About->Detail

Jconsole Plugin (JConsole Plug-in Wrapper Tab)

Click on 'JConsole Plugins'.
Click on 'Add JAR/Folder'  JDK_HOME/demo/management/JTop/JTop.jar
重启visualvm