jvm之JSTAT

http://java.sun.com/javase/6/docs/technotes/tools/share/jstat.html

SYNOPSIS

  

 jstat [ generalOption | outputOptions vmid [interval[s|ms] [count]] ]

PARAMETERS

    generalOption
        A single general command-line option (-help, -options, or -version)
    outputOptions
        One or more output options, consisting of a single statOption, plus any of the -t, -h, and -J options.
    vmid
        Virtual machine identifier, a string indicating the target Java virtual machine (JVM). The general syntax is

      

 [protocol:][//]lvmid[@hostname[:port]/servername]

        The syntax of the vmid string largely corresponds to the syntax of a URI. The vmid can vary from a simple integer representing a local JVM to a more complex construction specifying a communications protocol, port number, and other implementation-specific values. See Virtual Machine Identifier for details.
    interval[s|ms]
        Sampling interval in the specified units, seconds (s) or milliseconds (ms). Default units are milliseconds.  Must be a positive integer.  If specified, jstat will produce its output at each interval.
    count
        Number of samples to display. Default value is infinity; that is, jstat displays statistics until the target JVM terminates or the jstat command is terminated.  Must be a positive integer.

DESCRIPTION

    The jstat tool displays performance statistics for an instrumented HotSpot Java virtual machine (JVM). The target JVM is identified by its virtual machine identifier, or vmid option described below.

    NOTE: This utility is unsupported and may not be available in future versions of the JDK. It is not currently available on Windows 98 and Windows ME. platforms.

VIRTUAL MACHINE IDENTIFIER

    The syntax of the vmid string largely corresponds to the syntax of a URI:

  

 [protocol:][//]lvmid[@hostname][:port][/servername]

    protocol
        The communications protocol. If the protocol is omitted and a hostname is not specified, the default protocol is a platform specific optimized local protocol. If the protocol is omitted and a hostname is specified, then the default protocol is rmi.
    lvmid
        The local virtual machine identifier for the target JVM. The lvmid is a platform-specific value that uniquely identifies a JVM on a system. The lvmid is the only required component of a virtual machine identifier. The lvmid is typically, but not necessarily, the operating system's process identifier for the target JVM process. You can use the jps command to determine the lvmid. Also, you can determine lvmid on Unix platforms with the ps command, and on Windows with the Windows Task Manager.
    hostname
        A hostname or IP address indicating the target host. If hostname is omitted, then the target host is the local host.
    port
        The default port for communicating with the remote server. If the hostname is omitted or the protocol specifies an optimized, local protocol, then port is ignored. Otherwise, treatment of the port parameter is implementation specific. For the default rmi protocol, the port indicates the port number for the rmiregistry on the remote host. If port is omitted, and protocol indicates rmi, then the default rmiregistry port (1099) is used.
    servername
        The treatment of this parameter depends on implementation. For the optimized local protocol, this field is ignored. For the rmi protocol, it represents the name of the RMI remote object on the remote host.

OPTIONS

    The jstat command supports two types of options, general options and output options. General options cause jstat to display simple usage and version information. Output options determine the content and format of the statistical output.

    NOTE: All options, and their functionality are subject to change or removal in future releases.
    GENERAL OPTIONS

    If you specify one of the general options, you cannot specify any other option or parameter.

    -help
        Display help message.
    -version
        Display version information.
    -options
        Display list of statistics options. See the Output Options section below.

OUTPUT OPTIONS

    If you do not specify a general option, then you can specify output options. Output options determine the content and format of jstat's output, and consist of a single statOption, plus any of the other output options (-h, -t, and -J).  The statOption must come first.

    Output is formatted as a table, with columns are separated by spaces. A header row with titles describes the columns.  Use the -h option to set the frequency at which the header is displayed.  Column header names are generally consistent between the different options. In general, if two options provide a column with the same name, then the data source for the two columns are the same.

    Use the -t option to display a time stamp column, labeled Timestamp as the first column of output. The Timestamp column contains the elapsed time, in seconds, since startup of the target JVM. The resolution of the time stamp is dependent on various factors and is subject to variation due to delayed thread scheduling on heavily loaded systems.

    Use the interval and count parameters to determine how frequently and how many times, respectively, jstat displays its output.

    NOTE: You are advised not to write scripts to parse jstat's output since the format may change in future releases. If you choose to write scripts that parse jstat output, expect to modify them for future releases of this tool.

    -statOption
        Determines the statistics information that jstat displays. The following table lists the available options.  Use the -options general option to display the list of options for a particular platform installation.

        Option Displays...
        class Statistics on the behavior of the class loader.
        compiler Statistics of the behavior of the HotSpot Just-in-Time compiler.
        gc Statistics of the behavior of the garbage collected heap.
        gccapacity Statistics of the capacities of the generations and their corresponding spaces.
        gccause Summary of garbage collection statistics (same as -gcutil), with the cause of the last and current (if applicable) garbage collection events.
        gcnew Statistics of the behavior of the new generation.
        gcnewcapacity Statistics of the sizes of the new generations and its corresponding spaces.
        gcold Statistics of the behavior of the old and permanent generations.
        gcoldcapacity Statistics of the sizes of the old generation.
        gcpermcapacity Statistics of the sizes of the permanent generation.
        gcutil Summary of garbage collection statistics.
        printcompilation HotSpot compilation method statistics.
    -h n
        Display a column header every n samples (output rows), where n is a positive integer. Default value is 0, which displays the column header above the first row of data.
    -t n
        Display a timestamp column as the first column of output. The timestamp is the the time since the start time of the target JVM.
    -JjavaOption
        Pass javaOption to the java application launcher. For example, -J-Xms48m sets the startup memory to 48 megabytes. For a complete list of options, see java - the Java application launcher

STATOPTIONS AND OUTPUT

    The following tables summarize the columns that jstat outputs for each statOption.
    -class Option

    Class Loader Statistics Column 	Description
    Loaded 	Number of classes loaded.
    Bytes 	Number of Kbytes loaded.
    Unloaded 	Number of classes unloaded.
    Bytes 	Number of Kbytes unloaded.
    Time 	Time spent performing class load and unload operations.

    -compiler Option
   

HotSpot Just-In-Time Compiler Statistics Column 	Description
    Compiled 	Number of compilation tasks performed.
    Failed 	Number of compilation tasks that failed.
    Invalid 	Number of compilation tasks that were invalidated.
    Time 	Time spent performing compilation tasks.
    FailedType 	Compile type of the last failed compilation.
    FailedMethod 	Class name and method for the last failed compilation.

    -gc Option
   

Garbage-collected heap statistics Column 	Description
    S0C 	Current survivor space 0 capacity (KB).
    S1C 	Current survivor space 1 capacity (KB).
    S0U 	Survivor space 0 utilization (KB).
    S1U 	Survivor space 1 utilization (KB).
    EC 	Current eden space capacity (KB).
    EU 	Eden space utilization (KB).
    OC 	Current old space capacity (KB).
    OU 	Old space utilization (KB).
    PC 	Current permanent space capacity (KB).
    PU 	Permanent space utilization (KB).
    YGC 	Number of young generation GC Events.
    YGCT 	Young generation garbage collection time.
    FGC 	Number of full GC events.
    FGCT 	Full garbage collection time.
    GCT 	Total garbage collection time.

    -gccapacity Option
   

Memory Pool Generation and Space Capacities Column 	Description
    NGCMN 	Minimum new generation capacity (KB).
    NGCMX 	Maximum new generation capacity (KB).
    NGC 	Current new generation capacity (KB).
    S0C 	Current survivor space 0 capacity (KB).
    S1C 	Current survivor space 1 capacity (KB).
    EC 	Current eden space capacity (KB).
    OGCMN 	Minimum old generation capacity (KB).
    OGCMX 	Maximum old generation capacity (KB).
    OGC 	Current old generation capacity (KB).
    OC 	Current old space capacity (KB).
    PGCMN 	Minimum permanent generation capacity (KB).
    PGCMX 	Maximum Permanent generation capacity (KB).
    PGC 	Current Permanent generation capacity (KB).
    PC 	Current Permanent space capacity (KB).
    YGC 	Number of Young generation GC Events.
    FGC 	Number of Full GC Events.

    -gccause Option

    This option displays the same summary of garbage collection statistics as the -gcutil option, but includes the causes of the last garbage collection event and (if applicable) the current garbage collection event. In addition to the columns listed for -gcutil, this option adds the following columns:
    Garbage Collection Statistics, Including GC Events Column Description
    LGCC Cause of last Garbage Collection.
    GCC Cause of current Garbage Collection.
    -gcnew Option
   

New Generation Statistics Column 	Description
    S0C 	Current survivor space 0 capacity (KB).
    S1C 	Current survivor space 1 capacity (KB).
    S0U 	Survivor space 0 utilization (KB).
    S1U 	Survivor space 1 utilization (KB).
    TT 	Tenuring threshold.
    MTT 	Maximum tenuring threshold.
    DSS 	Desired survivor size (KB).
    EC 	Current eden space capacity (KB).
    EU 	Eden space utilization (KB).
    YGC 	Number of young generation GC events.
    YGCT 	Young generation garbage collection time.

    -gcnewcapacity Option
   

New Generation Space Size Statistics Column 	Description
    NGCMN          
    	Minimum new generation capacity (KB).
    NGCMX     	Maximum new generation capacity (KB).
    NGC     	Current new generation capacity (KB).
    S0CMX 	Maximum survivor space 0 capacity (KB).
    S0C 	Current survivor space 0 capacity (KB).
    S1CMX 	Maximum survivor space 1 capacity (KB).
    S1C 	Current survivor space 1 capacity (KB).
    ECMX 	Maximum eden space capacity (KB).
    EC 	Current eden space capacity (KB).
    YGC 	Number of young generation GC events.
    FGC 	Number of Full GC Events.

    -gcold Option
   

Old and Permanent Generation Statistics Column 	Description
    PC 	Current permanent space capacity (KB).
    PU 	Permanent space utilization (KB).
    OC 	Current old space capacity (KB).
    OU 	old space utilization (KB).
    YGC 	Number of young generation GC events.
    FGC 	Number of full GC events.
    FGCT 	Full garbage collection time.
    GCT 	Total garbage collection time.

    -gcoldcapacity Option
   

Old Generation Statistics Column 	Description
    OGCMN 	Minimum old generation capacity (KB).
    OGCMX 	Maximum old generation capacity (KB).
    OGC 	Current old generation capacity (KB).
    OC 	Current old space capacity (KB).
    YGC 	Number of young generation GC events.
    FGC 	Number of full GC events.
    FGCT 	Full garbage collection time.
    GCT 	Total garbage collection time.

    -gcpermcapacity Option
   

Permanent Generation Statistics Column 	Description
    PGCMN 	Minimum permanent generation capacity (KB).
    PGCMX 	Maximum permanent generation capacity (KB).
    PGC 	Current permanent generation capacity (KB).
    PC 	Current permanent space capacity (KB).
    YGC 	Number of young generation GC events.
    FGC 	Number of full GC events.
    FGCT 	Full garbage collection time.
    GCT 	Total garbage collection time.

    -gcutil Option
   

Summary of Garbage Collection Statistics Column 	Description
    S0 	Survivor space 0 utilization as a percentage of the space's current capacity.
    S1 	Survivor space 1 utilization as a percentage of the space's current capacity.
    E 	Eden space utilization as a percentage of the space's current capacity.
    O 	Old space utilization as a percentage of the space's current capacity.
    P 	Permanent space utilization as a percentage of the space's current capacity.
    YGC 	Number of young generation GC events.
    YGCT 	Young generation garbage collection time.
    FGC 	Number of full GC events.
    FGCT 	Full garbage collection time.
    GCT 	Total garbage collection time.

    -printcompilation Option
   

HotSpot Compiler Method Statistics Column 	Description
    Compiled 	Number of compilation tasks performed.
    Size 	Number of bytes of bytecode for the method.
    Type 	Compilation type.
    Method 	Class name and method name identifying the compiled method. Class name uses "/" instead of "." as namespace separator. Method name is the method within the given class. The format for these two fields is consistent with the HotSpot - XX:+PrintComplation option.

    This section presents some examples of monitoring a local JVM with a lvmid of 21891.
    Using the gcutil option

    This example attaches to lvmid 21891 and takes 7 samples at 250 millisecond intervals and displays the output as specified by the -gcutil option.

    jstat -gcutil 21891 250 7

      S0     S1     E      O      P     YGC    YGCT    FGC    FGCT     GCT

     12.44   0.00  27.20   9.49  96.70    78    0.176     5    0.495    0.672

     12.44   0.00  62.16   9.49  96.70    78    0.176     5    0.495    0.672

     12.44   0.00  83.97   9.49  96.70    78    0.176     5    0.495    0.672

      0.00   7.74   0.00   9.51  96.70    79    0.177     5    0.495    0.673

      0.00   7.74  23.37   9.51  96.70    79    0.177     5    0.495    0.673

      0.00   7.74  43.82   9.51  96.70    79    0.177     5    0.495    0.673

      0.00   7.74  58.11   9.51  96.71    79    0.177     5    0.495    0.673

    The output of this example shows that a young generation collection occurred between the 3rd and 4th sample. The collection took 0.001 seconds and promoted objects from the eden space (E) to the old space (O), resulting in an increase of old space utilization from 9.49% to 9.51%. Before the collection, the survivor space was 12.44% utilized, but after this collection it is only 7.74% utilized.
    Repeating the column header string

    This example attaches to lvmid 21891 and takes samples at 250 millisecond intervals and displays the output as specified by -gcutil option. In addition, it uses the -h3 option to output the column header after every 3 lines of data.

    jstat -gcnew -h3 21891 250

     S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT

      64.0   64.0    0.0   31.7 31  31   32.0    512.0    178.6    249    0.203

      64.0   64.0    0.0   31.7 31  31   32.0    512.0    355.5    249    0.203

      64.0   64.0   35.4    0.0  2  31   32.0    512.0     21.9    250    0.204

     S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT

      64.0   64.0   35.4    0.0  2  31   32.0    512.0    245.9    250    0.204

      64.0   64.0   35.4    0.0  2  31   32.0    512.0    421.1    250    0.204

      64.0   64.0    0.0   19.0 31  31   32.0    512.0     84.4    251    0.204

     S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT

      64.0   64.0    0.0   19.0 31  31   32.0    512.0    306.7    251    0.204

    In addition to showing the repeating header string, this example shows that between the 2nd and 3rd samples, a young GC occurred. Its duration was 0.001 seconds. The collection found enough live data that the survivor space 0 utilization (S0U) would would have exceeded the desired survivor Size (DSS). As a result, objects were promoted to the old generation (not visible in this output), and the tenuring threshold (TT) was lowered from 31 to 2.

    Another collection occurs between the 5th and 6th samples. This collection found very few survivors and returned the tenuring threshold to 31.
    Including a time stamp for each sample

    This example attaches to lvmid 21891 and takes 3 samples at 250 millisecond intervals. The -t option is used to generate a time stamp for each sample in the first column.

    jstat -gcoldcapacity -t 21891 250 3

    Timestamp          OGCMN        OGCMX         OGC           OC       YGC   FGC    FGCT    GCT

              150.1       1408.0      60544.0      11696.0      11696.0   194    80    2.874   3.799

              150.4       1408.0      60544.0      13820.0      13820.0   194    81    2.938   3.863

              150.7       1408.0      60544.0      13820.0      13820.0   194    81    2.938   3.863

    The Timestamp column reports the elapsed time in seconds since the start of the target JVM. In addition, the -gcoldcapacity output shows the old generation capacity (OGC) and the old space capacity (OC) increasing as the heap expands to meet allocation and/or promotion demands. The old generation capacity (OGC) has grown to from 11696 KB to 13820 KB after the 81st Full GC (FGC). The maximum capacity of the generation (and space) is 60544 KB (OGCMX), so it still has room to expand.
    Monitor instrumentation for a remote JVM

    This example attaches to lvmid 40496 on the system named remote.domain using the -gcutil option, with samples taken every second indefinitely.

    jstat -gcutil [e-mail] 1000

    ... output omitted

    The lvmid is combined with the name of the remote host to construct a vmid of [e-mail]. This vmid results in the use of the rmi protocol to communicate to the default jstatd server on the remote host. The jstatd server is located using the rmiregistry on remote.domain that is bound to the default rmiregistry port (port 1099).