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jstat(1)                         JDK Commands                         jstat(1)




NAME

       jstat - monitor JVM statistics


SYNOPSIS

       Note: This command is experimental and unsupported.

       jstat generalOptions

       jstat outputOptions [-t] [-h lines] vmid [interval [count]]

       generalOptions
              A single general command-line option.  See General Options.

       outputOptions
              An  option  reported by the -options option.  One or more output
              options that consist of a single statOption, plus any of the -t,
              -h, and -J options.  See Output Options for the jstat Command.

       -t     Displays a time-stamp column as the first column of output.  The
              time stamp is the time since the start time of the target JVM.

       -h n   Displays a column header every n samples (output rows), where  n
              is  a  positive integer.  The default value is 0, which displays
              the column header of the first row of data.

       vmid   A virtual machine identifier, which is a string  that  indicates
              the target JVM.  See Virtual Machine Identifier.

       interval
              The  sampling  interval  in  the specified units, seconds (s) or
              milliseconds (ms).  Default units are milliseconds.   This  must
              be  a  positive integer.  When specified, the jstat command pro-
              duces its output at each interval.

       count  The number of samples to display.  The default value is  infini-
              ty,  which  causes the jstat command to display statistics until
              the target JVM terminates or the jstat  command  is  terminated.
              This value must be a positive integer.


DESCRIPTION

       The  jstat  command displays performance statistics for an instrumented
       Java HotSpot VM.  The target JVM is identified by its  virtual  machine
       identifier, or vmid option.

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

       All options and their functionality are subject to change or removal in
       future releases.


GENERAL OPTIONS

       If  you  specify one of the general options, then you can't specify any
       other option or parameter.

       -help  Displays a help message.

       -options
              Displays a list of static options.  See Output Options  for  the
              jstat Command.


OUTPUT OPTIONS FOR THE JSTAT COMMAND

       If  you don't specify a general option, then you can specify output op-
       tions.  Output options determine the content and format  of  the  jstat
       command'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 that are separated by spa-
       ces.  A header row with titles describes the columns.  Use the  -h  op-
       tion  to  set  the  frequency at which the header is displayed.  Column
       header names are consistent among the different options.   In  general,
       if  two  options  provide  a  column  with the same name, then the data
       source for the two columns is 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 the target JVM started.  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, the jstat command displays its output.

       Note:

       Don't  write  scripts  to  parse the jstat command's output because the
       format might change in future releases.   If  you  write  scripts  that
       parse  the  jstat command output, then expect to modify them for future
       releases of this tool.

       -statOption
              Determines the statistics information  that  the  jstat  command
              displays.   The  following lists the available options.  Use the
              -options general option to display the list  of  options  for  a
              particular  platform installation.  See Stat Options and Output.

              class: Displays statistics about the behavior of the class load-
              er.

              compiler:  Displays  statistics  about  the behavior of the Java
              HotSpot VM Just-in-Time compiler.

              gc: Displays statistics about the behavior of the  garbage  col-
              lected heap.

              gccapacity: Displays statistics about the capacities of the gen-
              erations 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 about the behavior of the new genera-
              tion.

              gcnewcapacity:  Displays  statistics  about the sizes of the new
              generations and their corresponding spaces.

              gcold: Displays statistics about the behavior of the old genera-
              tion 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.

       -JjavaOption
              Passes  javaOption  to the Java application launcher.  For exam-
              ple, -J-Xms48m sets the startup memory to 48 MB.  For a complete
              list of options, see java.


STAT OPTIONS AND OUTPUT

       The following information summarizes the columns that the jstat command
       outputs for each statOption.

       -class option
              Class loader statistics.

              Loaded: Number of classes loaded.

              Bytes: Number of KB loaded.

              Unloaded: Number of classes unloaded.

              Bytes: Number of KB loaded.

              Time: Time spent performing class loading and  unloading  opera-
              tions.

       -compiler option
              Java HotSpot VM Just-in-Time compiler statistics.

              Compiled: Number of compilation tasks performed.

              Failed: Number of compilations tasks 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 of the last failed compila-
              tion.

       -gc option
              Garbage collected heap statistics.

              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).

              MC: Metaspace Committed Size (KB).

              MU: Metaspace utilization (KB).

              CCSC: Compressed class committed size (KB).

              CCSU: Compressed class space used (KB).

              YGC: Number of young generation garbage collection (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.

              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).

              MCMN: Minimum metaspace capacity (KB).

              MCMX: Maximum metaspace capacity (KB).

              MC: Metaspace Committed Size (KB).

              CCSMN: Compressed class space minimum capacity (KB).

              CCSMX: Compressed class space maximum capacity (KB).

              CCSC: Compressed class committed size (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 sta-
              tistics as the -gcutil option, but includes the  causes  of  the
              last garbage collection event and (when applicable), the current
              garbage collection event.  In addition to the columns listed for
              -gcutil, this option adds the following columns:

              LGCC: Cause of last garbage collection

              GCC: Cause of current garbage collection

       -gcnew option
              New generation statistics.

              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.

              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 generation size statistics.

              MC: Metaspace Committed Size (KB).

              MU: Metaspace utilization (KB).

              CCSC: Compressed class committed size (KB).

              CCSU: Compressed class space used (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.

              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.

       -gcmetacapacity option
              Metaspace size statistics.

              MCMN: Minimum metaspace capacity (KB).

              MCMX: Maximum metaspace capacity (KB).

              MC: Metaspace Committed Size (KB).

              CCSMN: Compressed class space minimum capacity (KB).

              CCSMX: Compressed class space maximum 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.

              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.

              M:  Metaspace utilization as a percentage of the space's current
              capacity.

              CCS: Compressed class space utilization as a percentage.

              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
              Java HotSpot VM compiler method statistics.

              Compiled: Number of compilation tasks performed by the most  re-
              cently compiled method.

              Size: Number of bytes of byte code of the most recently compiled
              method.

              Type: Compilation type of the most recently compiled method.

              Method: Class name and method name identifying the most recently
              compiled  method.   Class name uses a slash (/) instead of a dot
              (.) as a name space separator.  The method name  is  the  method
              within  the specified class.  The format for these two fields is
              consistent with the HotSpot -XX:+PrintCompilation option.


VIRTUAL MACHINE IDENTIFIER

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

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

       The syntax of the vmid string corresponds to the syntax of a URI.   The
       vmid  string can vary from a simple integer that represents a local JVM
       to a more complex construction that specifies a  communications  proto-
       col, port number, and other implementation-specific values.

       protocol
              The  communications  protocol.  If the protocol value is omitted
              and a host name isn't specified, then the default protocol is  a
              platform-specific  optimized  local  protocol.   If the protocol
              value is omitted and a host name 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  provided the JVM processes is not running in a sepa-
              rate docker instance.  You can also determine the lvmid on Linux
              and  OS X platforms with the ps command, and on Windows with the
              Windows Task Manager.

       hostname
              A host name or IP address that indicates the  target  host.   If
              the hostname value is omitted, then the target host is the local
              host.

       port   The default port for communicating with the remote  server.   If
              the hostname value is omitted or the protocol value specifies an
              optimized, local protocol, then the port value is ignored.  Oth-
              erwise,  treatment  of the port parameter is implementation-spe-
              cific.  For the default rmi protocol, the port  value  indicates
              the  port number for the rmiregistry on the remote host.  If the
              port value is omitted and the protocol value indicates rmi, then
              the default rmiregistry port (1099) is used.

       servername
              The treatment of the servername parameter depends on implementa-
              tion.  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.


EXAMPLES

       This section presents some examples of monitoring a local JVM  with  an
       lvmid of 21891.


THE GCUTIL OPTION

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

       The output of this example shows that a young generation collection oc-
       curred between the third and fourth sample.  The collection took  0.078
       seconds  and  promoted objects from the eden space (E) to the old space
       (O), resulting in an increase of old space utilization from  66.80%  to
       68.19%.  Before the collection, the survivor space was 97.02% utilized,
       but after this collection it's 91.03% utilized.

              jstat -gcutil 21891 250 7
                S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT
                0.00  97.02  70.31  66.80  95.52  89.14      7    0.300     0    0.000    0.300
                0.00  97.02  86.23  66.80  95.52  89.14      7    0.300     0    0.000    0.300
                0.00  97.02  96.53  66.80  95.52  89.14      7    0.300     0    0.000    0.300
               91.03   0.00   1.98  68.19  95.89  91.24      8    0.378     0    0.000    0.378
               91.03   0.00  15.82  68.19  95.89  91.24      8    0.378     0    0.000    0.378
               91.03   0.00  17.80  68.19  95.89  91.24      8    0.378     0    0.000    0.378
               91.03   0.00  17.80  68.19  95.89  91.24      8    0.378     0    0.000    0.378


REPEAT THE COLUMN HEADER STRING

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

       In  addition to showing the repeating header string, this example shows
       that between the second and third samples, a young  GC  occurred.   Its
       duration  was  0.001  seconds.  The collection found enough active data
       that the survivor space 0 utilization (S0U) would have exceeded the de-
       sired  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 fifth and sixth samples.  This
       collection found very few survivors and returned the tenuring threshold
       to 31.

              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


INCLUDE A TIME STAMP FOR EACH SAMPLE

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

       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) in-
       creasing as the heap expands to meet allocation or  promotion  demands.
       The old generation capacity (OGC) has grown from 11,696 KB to 13,820 KB
       after the eighty-first full garbage collection (FGC).  The maximum  ca-
       pacity  of the generation (and space) is 60,544 KB (OGCMX), so it still
       has room to expand.

              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


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.

       The lvmid is combined with the name of the remote host to  construct  a
       vmid  of  40496@remote.domain.  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 command on
       remote.domain that's bound to the default port of the rmiregistry  com-
       mand (port 1099).

              jstat -gcutil 40496@remote.domain 1000
              ... output omitted



JDK 15                               2020                             jstat(1)

openjdk 15.0.2 - Generated Tue Feb 23 16:14:51 CST 2021
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