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| .TH "JSTAT" "1" "2023" "JDK 21" "JDK Commands" |
| .hy |
| .SH NAME |
| .PP |
| jstat - monitor JVM statistics |
| .SH SYNOPSIS |
| .PP |
| \f[B]Note:\f[R] This command is experimental and unsupported. |
| .PP |
| \f[V]jstat\f[R] \f[I]generalOptions\f[R] |
| .PP |
| \f[V]jstat\f[R] \f[I]outputOptions\f[R] [\f[V]-t\f[R]] [\f[V]-h\f[R] |
| \f[I]lines\f[R]] \f[I]vmid\f[R] [\f[I]interval\f[R] [\f[I]count\f[R]]] |
| .TP |
| \f[I]generalOptions\f[R] |
| A single general command-line option. |
| See \f[B]General Options\f[R]. |
| .TP |
| \f[I]outputOptions\f[R] |
| An option reported by the \f[V]-options\f[R] option. |
| One or more output options that consist of a single |
| \f[V]statOption\f[R], plus any of the \f[V]-t\f[R], \f[V]-h\f[R], and |
| \f[V]-J\f[R] options. |
| See \f[B]Output Options for the jstat Command\f[R]. |
| .TP |
| \f[V]-t\f[R] |
| 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. |
| .TP |
| \f[V]-h\f[R] \f[I]n\f[R] |
| Displays a column header every \f[I]n\f[R] samples (output rows), where |
| \f[I]n\f[R] is a positive integer. |
| The default value is \f[V]0\f[R], which displays the column header of |
| the first row of data. |
| .TP |
| \f[I]vmid\f[R] |
| A virtual machine identifier, which is a string that indicates the |
| target JVM. |
| See \f[B]Virtual Machine Identifier\f[R]. |
| .TP |
| \f[I]interval\f[R] |
| 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 \f[V]jstat\f[R] command produces its output at each |
| interval. |
| .TP |
| \f[I]count\f[R] |
| The number of samples to display. |
| The default value is infinity, which causes the \f[V]jstat\f[R] command |
| to display statistics until the target JVM terminates or the |
| \f[V]jstat\f[R] command is terminated. |
| This value must be a positive integer. |
| .SH DESCRIPTION |
| .PP |
| The \f[V]jstat\f[R] command displays performance statistics for an |
| instrumented Java HotSpot VM. |
| The target JVM is identified by its virtual machine identifier, or |
| \f[V]vmid\f[R] option. |
| .PP |
| The \f[V]jstat\f[R] command supports two types of options, general |
| options and output options. |
| General options cause the \f[V]jstat\f[R] command to display simple |
| usage and version information. |
| Output options determine the content and format of the statistical |
| output. |
| .PP |
| All options and their functionality are subject to change or removal in |
| future releases. |
| .SH GENERAL OPTIONS |
| .PP |
| If you specify one of the general options, then you can\[aq]t specify |
| any other option or parameter. |
| .TP |
| \f[V]-help\f[R] |
| Displays a help message. |
| .TP |
| \f[V]-options\f[R] |
| Displays a list of static options. |
| See \f[B]Output Options for the jstat Command\f[R]. |
| .SH OUTPUT OPTIONS FOR THE JSTAT COMMAND |
| .PP |
| If you don\[aq]t specify a general option, then you can specify output |
| options. |
| Output options determine the content and format of the \f[V]jstat\f[R] |
| command\[aq]s output, and consist of a single \f[V]statOption\f[R], plus |
| any of the other output options (\f[V]-h\f[R], \f[V]-t\f[R], and |
| \f[V]-J\f[R]). |
| The \f[V]statOption\f[R] must come first. |
| .PP |
| Output is formatted as a table, with columns that are separated by |
| spaces. |
| A header row with titles describes the columns. |
| Use the \f[V]-h\f[R] option 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. |
| .PP |
| Use the \f[V]-t\f[R] 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. |
| .PP |
| Use the interval and count parameters to determine how frequently and |
| how many times, respectively, the \f[V]jstat\f[R] command displays its |
| output. |
| .PP |
| \f[B]Note:\f[R] |
| .PP |
| Don\[aq]t write scripts to parse the \f[V]jstat\f[R] command\[aq]s |
| output because the format might change in future releases. |
| If you write scripts that parse the \f[V]jstat\f[R] command output, then |
| expect to modify them for future releases of this tool. |
| .TP |
| \f[V]-statOption\f[R] |
| Determines the statistics information that the \f[V]jstat\f[R] command |
| displays. |
| The following lists the available options. |
| Use the \f[V]-options\f[R] general option to display the list of options |
| for a particular platform installation. |
| See \f[B]Stat Options and Output\f[R]. |
| .RS |
| .PP |
| \f[V]class\f[R]: Displays statistics about the behavior of the class |
| loader. |
| .PP |
| \f[V]compiler\f[R]: Displays statistics about the behavior of the Java |
| HotSpot VM Just-in-Time compiler. |
| .PP |
| \f[V]gc\f[R]: Displays statistics about the behavior of the garbage |
| collected heap. |
| .PP |
| \f[V]gccapacity\f[R]: Displays statistics about the capacities of the |
| generations and their corresponding spaces. |
| .PP |
| \f[V]gccause\f[R]: Displays a summary about garbage collection |
| statistics (same as \f[V]-gcutil\f[R]), with the cause of the last and |
| current (when applicable) garbage collection events. |
| .PP |
| \f[V]gcnew\f[R]: Displays statistics about the behavior of the new |
| generation. |
| .PP |
| \f[V]gcnewcapacity\f[R]: Displays statistics about the sizes of the new |
| generations and their corresponding spaces. |
| .PP |
| \f[V]gcold\f[R]: Displays statistics about the behavior of the old |
| generation and metaspace statistics. |
| .PP |
| \f[V]gcoldcapacity\f[R]: Displays statistics about the sizes of the old |
| generation. |
| .PP |
| \f[V]gcmetacapacity\f[R]: Displays statistics about the sizes of the |
| metaspace. |
| .PP |
| \f[V]gcutil\f[R]: Displays a summary about garbage collection |
| statistics. |
| .PP |
| \f[V]printcompilation\f[R]: Displays Java HotSpot VM compilation method |
| statistics. |
| .RE |
| .TP |
| \f[V]-J\f[R]\f[I]javaOption\f[R] |
| Passes \f[I]javaOption\f[R] to the Java application launcher. |
| For example, \f[V]-J-Xms48m\f[R] sets the startup memory to 48 MB. |
| For a complete list of options, see \f[B]java\f[R]. |
| .SH STAT OPTIONS AND OUTPUT |
| .PP |
| The following information summarizes the columns that the |
| \f[V]jstat\f[R] command outputs for each \f[I]statOption\f[R]. |
| .TP |
| \f[V]-class\f[R] \f[I]option\f[R] |
| Class loader statistics. |
| .RS |
| .PP |
| \f[V]Loaded\f[R]: Number of classes loaded. |
| .PP |
| \f[V]Bytes\f[R]: Number of KB loaded. |
| .PP |
| \f[V]Unloaded\f[R]: Number of classes unloaded. |
| .PP |
| \f[V]Bytes\f[R]: Number of KB unloaded. |
| .PP |
| \f[V]Time\f[R]: Time spent performing class loading and unloading |
| operations. |
| .RE |
| .TP |
| \f[V]-compiler\f[R] \f[I]option\f[R] |
| Java HotSpot VM Just-in-Time compiler statistics. |
| .RS |
| .PP |
| \f[V]Compiled\f[R]: Number of compilation tasks performed. |
| .PP |
| \f[V]Failed\f[R]: Number of compilations tasks failed. |
| .PP |
| \f[V]Invalid\f[R]: Number of compilation tasks that were invalidated. |
| .PP |
| \f[V]Time\f[R]: Time spent performing compilation tasks. |
| .PP |
| \f[V]FailedType\f[R]: Compile type of the last failed compilation. |
| .PP |
| \f[V]FailedMethod\f[R]: Class name and method of the last failed |
| compilation. |
| .RE |
| .TP |
| \f[V]-gc\f[R] \f[I]option\f[R] |
| Garbage collected heap statistics. |
| .RS |
| .PP |
| \f[V]S0C\f[R]: Current survivor space 0 capacity (KB). |
| .PP |
| \f[V]S1C\f[R]: Current survivor space 1 capacity (KB). |
| .PP |
| \f[V]S0U\f[R]: Survivor space 0 utilization (KB). |
| .PP |
| \f[V]S1U\f[R]: Survivor space 1 utilization (KB). |
| .PP |
| \f[V]EC\f[R]: Current eden space capacity (KB). |
| .PP |
| \f[V]EU\f[R]: Eden space utilization (KB). |
| .PP |
| \f[V]OC\f[R]: Current old space capacity (KB). |
| .PP |
| \f[V]OU\f[R]: Old space utilization (KB). |
| .PP |
| \f[V]MC\f[R]: Metaspace Committed Size (KB). |
| .PP |
| \f[V]MU\f[R]: Metaspace utilization (KB). |
| .PP |
| \f[V]CCSC\f[R]: Compressed class committed size (KB). |
| .PP |
| \f[V]CCSU\f[R]: Compressed class space used (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation garbage collection (GC) |
| events. |
| .PP |
| \f[V]YGCT\f[R]: Young generation garbage collection time. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .PP |
| \f[V]FGCT\f[R]: Full garbage collection time. |
| .PP |
| \f[V]GCT\f[R]: Total garbage collection time. |
| .RE |
| .TP |
| \f[V]-gccapacity\f[R] \f[I]option\f[R] |
| Memory pool generation and space capacities. |
| .RS |
| .PP |
| \f[V]NGCMN\f[R]: Minimum new generation capacity (KB). |
| .PP |
| \f[V]NGCMX\f[R]: Maximum new generation capacity (KB). |
| .PP |
| \f[V]NGC\f[R]: Current new generation capacity (KB). |
| .PP |
| \f[V]S0C\f[R]: Current survivor space 0 capacity (KB). |
| .PP |
| \f[V]S1C\f[R]: Current survivor space 1 capacity (KB). |
| .PP |
| \f[V]EC\f[R]: Current eden space capacity (KB). |
| .PP |
| \f[V]OGCMN\f[R]: Minimum old generation capacity (KB). |
| .PP |
| \f[V]OGCMX\f[R]: Maximum old generation capacity (KB). |
| .PP |
| \f[V]OGC\f[R]: Current old generation capacity (KB). |
| .PP |
| \f[V]OC\f[R]: Current old space capacity (KB). |
| .PP |
| \f[V]MCMN\f[R]: Minimum metaspace capacity (KB). |
| .PP |
| \f[V]MCMX\f[R]: Maximum metaspace capacity (KB). |
| .PP |
| \f[V]MC\f[R]: Metaspace Committed Size (KB). |
| .PP |
| \f[V]CCSMN\f[R]: Compressed class space minimum capacity (KB). |
| .PP |
| \f[V]CCSMX\f[R]: Compressed class space maximum capacity (KB). |
| .PP |
| \f[V]CCSC\f[R]: Compressed class committed size (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .RE |
| .TP |
| \f[V]-gccause\f[R] \f[I]option\f[R] |
| This option displays the same summary of garbage collection statistics |
| as the \f[V]-gcutil\f[R] 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 \f[V]-gcutil\f[R], this option |
| adds the following columns: |
| .RS |
| .PP |
| \f[V]LGCC\f[R]: Cause of last garbage collection |
| .PP |
| \f[V]GCC\f[R]: Cause of current garbage collection |
| .RE |
| .TP |
| \f[V]-gcnew\f[R] \f[I]option\f[R] |
| New generation statistics. |
| .RS |
| .PP |
| \f[V]S0C\f[R]: Current survivor space 0 capacity (KB). |
| .PP |
| \f[V]S1C\f[R]: Current survivor space 1 capacity (KB). |
| .PP |
| \f[V]S0U\f[R]: Survivor space 0 utilization (KB). |
| .PP |
| \f[V]S1U\f[R]: Survivor space 1 utilization (KB). |
| .PP |
| \f[V]TT\f[R]: Tenuring threshold. |
| .PP |
| \f[V]MTT\f[R]: Maximum tenuring threshold. |
| .PP |
| \f[V]DSS\f[R]: Desired survivor size (KB). |
| .PP |
| \f[V]EC\f[R]: Current eden space capacity (KB). |
| .PP |
| \f[V]EU\f[R]: Eden space utilization (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]YGCT\f[R]: Young generation garbage collection time. |
| .RE |
| .TP |
| \f[V]-gcnewcapacity\f[R] \f[I]option\f[R] |
| New generation space size statistics. |
| .RS |
| .PP |
| \f[V]NGCMN\f[R]: Minimum new generation capacity (KB). |
| .PP |
| \f[V]NGCMX\f[R]: Maximum new generation capacity (KB). |
| .PP |
| \f[V]NGC\f[R]: Current new generation capacity (KB). |
| .PP |
| \f[V]S0CMX\f[R]: Maximum survivor space 0 capacity (KB). |
| .PP |
| \f[V]S0C\f[R]: Current survivor space 0 capacity (KB). |
| .PP |
| \f[V]S1CMX\f[R]: Maximum survivor space 1 capacity (KB). |
| .PP |
| \f[V]S1C\f[R]: Current survivor space 1 capacity (KB). |
| .PP |
| \f[V]ECMX\f[R]: Maximum eden space capacity (KB). |
| .PP |
| \f[V]EC\f[R]: Current eden space capacity (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .RE |
| .TP |
| \f[V]-gcold\f[R] \f[I]option\f[R] |
| Old generation size statistics. |
| .RS |
| .PP |
| \f[V]MC\f[R]: Metaspace Committed Size (KB). |
| .PP |
| \f[V]MU\f[R]: Metaspace utilization (KB). |
| .PP |
| \f[V]CCSC\f[R]: Compressed class committed size (KB). |
| .PP |
| \f[V]CCSU\f[R]: Compressed class space used (KB). |
| .PP |
| \f[V]OC\f[R]: Current old space capacity (KB). |
| .PP |
| \f[V]OU\f[R]: Old space utilization (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .PP |
| \f[V]FGCT\f[R]: Full garbage collection time. |
| .PP |
| \f[V]GCT\f[R]: Total garbage collection time. |
| .RE |
| .TP |
| \f[V]-gcoldcapacity\f[R] \f[I]option\f[R] |
| Old generation statistics. |
| .RS |
| .PP |
| \f[V]OGCMN\f[R]: Minimum old generation capacity (KB). |
| .PP |
| \f[V]OGCMX\f[R]: Maximum old generation capacity (KB). |
| .PP |
| \f[V]OGC\f[R]: Current old generation capacity (KB). |
| .PP |
| \f[V]OC\f[R]: Current old space capacity (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .PP |
| \f[V]FGCT\f[R]: Full garbage collection time. |
| .PP |
| \f[V]GCT\f[R]: Total garbage collection time. |
| .RE |
| .TP |
| \f[V]-gcmetacapacity\f[R] \f[I]option\f[R] |
| Metaspace size statistics. |
| .RS |
| .PP |
| \f[V]MCMN\f[R]: Minimum metaspace capacity (KB). |
| .PP |
| \f[V]MCMX\f[R]: Maximum metaspace capacity (KB). |
| .PP |
| \f[V]MC\f[R]: Metaspace Committed Size (KB). |
| .PP |
| \f[V]CCSMN\f[R]: Compressed class space minimum capacity (KB). |
| .PP |
| \f[V]CCSMX\f[R]: Compressed class space maximum capacity (KB). |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .PP |
| \f[V]FGCT\f[R]: Full garbage collection time. |
| .PP |
| \f[V]GCT\f[R]: Total garbage collection time. |
| .RE |
| .TP |
| \f[V]-gcutil\f[R] \f[I]option\f[R] |
| Summary of garbage collection statistics. |
| .RS |
| .PP |
| \f[V]S0\f[R]: Survivor space 0 utilization as a percentage of the |
| space\[aq]s current capacity. |
| .PP |
| \f[V]S1\f[R]: Survivor space 1 utilization as a percentage of the |
| space\[aq]s current capacity. |
| .PP |
| \f[V]E\f[R]: Eden space utilization as a percentage of the space\[aq]s |
| current capacity. |
| .PP |
| \f[V]O\f[R]: Old space utilization as a percentage of the space\[aq]s |
| current capacity. |
| .PP |
| \f[V]M\f[R]: Metaspace utilization as a percentage of the space\[aq]s |
| current capacity. |
| .PP |
| \f[V]CCS\f[R]: Compressed class space utilization as a percentage. |
| .PP |
| \f[V]YGC\f[R]: Number of young generation GC events. |
| .PP |
| \f[V]YGCT\f[R]: Young generation garbage collection time. |
| .PP |
| \f[V]FGC\f[R]: Number of full GC events. |
| .PP |
| \f[V]FGCT\f[R]: Full garbage collection time. |
| .PP |
| \f[V]GCT\f[R]: Total garbage collection time. |
| .RE |
| .TP |
| \f[V]-printcompilation\f[R] \f[I]option\f[R] |
| Java HotSpot VM compiler method statistics. |
| .RS |
| .PP |
| \f[V]Compiled\f[R]: Number of compilation tasks performed by the most |
| recently compiled method. |
| .PP |
| \f[V]Size\f[R]: Number of bytes of byte code of the most recently |
| compiled method. |
| .PP |
| \f[V]Type\f[R]: Compilation type of the most recently compiled method. |
| .PP |
| \f[V]Method\f[R]: 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 |
| \f[V]-XX:+PrintCompilation\f[R] option. |
| .RE |
| .SH VIRTUAL MACHINE IDENTIFIER |
| .PP |
| The syntax of the \f[V]vmid\f[R] string corresponds to the syntax of a |
| URI: |
| .RS |
| .PP |
| [\f[I]protocol\f[R]\f[V]:\f[R]][\f[V]//\f[R]]\f[I]lvmid\f[R][\f[V]\[at]\f[R]\f[I]hostname\f[R][\f[V]:\f[R]\f[I]port\f[R]][\f[V]/\f[R]\f[I]servername\f[R]] |
| .RE |
| .PP |
| The syntax of the \f[V]vmid\f[R] string corresponds to the syntax of a |
| URI. |
| The \f[V]vmid\f[R] string can vary from a simple integer that represents |
| a local JVM to a more complex construction that specifies a |
| communications protocol, port number, and other implementation-specific |
| values. |
| .TP |
| \f[I]protocol\f[R] |
| The communications protocol. |
| If the \f[I]protocol\f[R] value is omitted and a host name isn\[aq]t |
| specified, then the default protocol is a platform-specific optimized |
| local protocol. |
| If the \f[I]protocol\f[R] value is omitted and a host name is specified, |
| then the default protocol is \f[V]rmi\f[R]. |
| .TP |
| \f[I]lvmid\f[R] |
| The local virtual machine identifier for the target JVM. |
| The \f[I]lvmid\f[R] is a platform-specific value that uniquely |
| identifies a JVM on a system. |
| The \f[I]lvmid\f[R] is the only required component of a virtual machine |
| identifier. |
| The \f[I]lvmid\f[R] is typically, but not necessarily, the operating |
| system\[aq]s process identifier for the target JVM process. |
| You can use the \f[V]jps\f[R] command to determine the \f[I]lvmid\f[R] |
| provided the JVM processes is not running in a separate docker instance. |
| You can also determine the \f[I]lvmid\f[R] on Linux and macOS platforms |
| with the \f[V]ps\f[R] command, and on Windows with the Windows Task |
| Manager. |
| .TP |
| \f[I]hostname\f[R] |
| A host name or IP address that indicates the target host. |
| If the \f[I]hostname\f[R] value is omitted, then the target host is the |
| local host. |
| .TP |
| \f[I]port\f[R] |
| The default port for communicating with the remote server. |
| If the \f[I]hostname\f[R] value is omitted or the \f[I]protocol\f[R] |
| value specifies an optimized, local protocol, then the \f[I]port\f[R] |
| value is ignored. |
| Otherwise, treatment of the \f[I]port\f[R] parameter is |
| implementation-specific. |
| For the default \f[V]rmi\f[R] protocol, the port value indicates the |
| port number for the \f[V]rmiregistry\f[R] on the remote host. |
| If the \f[I]port\f[R] value is omitted and the \f[I]protocol\f[R] value |
| indicates \f[V]rmi\f[R], then the default rmiregistry port (1099) is |
| used. |
| .TP |
| \f[I]servername\f[R] |
| The treatment of the \f[I]servername\f[R] parameter depends on |
| implementation. |
| For the optimized local protocol, this field is ignored. |
| For the \f[V]rmi\f[R] protocol, it represents the name of the RMI remote |
| object on the remote host. |
| .SH EXAMPLES |
| .PP |
| This section presents some examples of monitoring a local JVM with an |
| \f[I]lvmid\f[R] of 21891. |
| .SH THE GCUTIL OPTION |
| .PP |
| This example attaches to lvmid 21891 and takes 7 samples at 250 |
| millisecond intervals and displays the output as specified by the |
| \f[V]-gcutil\f[R] option. |
| .PP |
| The output of this example shows that a young generation collection |
| occurred 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\[aq]s 91.03% utilized. |
| .IP |
| .nf |
| \f[CB] |
| 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 |
| \f[R] |
| .fi |
| .SH REPEAT THE COLUMN HEADER STRING |
| .PP |
| This example attaches to lvmid 21891 and takes samples at 250 |
| millisecond intervals and displays the output as specified by |
| \f[V]-gcnew\f[R] option. |
| In addition, it uses the \f[V]-h3\f[R] option to output the column |
| header after every 3 lines of data. |
| .PP |
| 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 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. |
| .PP |
| Another collection occurs between the fifth and sixth samples. |
| This collection found very few survivors and returned the tenuring |
| threshold to 31. |
| .IP |
| .nf |
| \f[CB] |
| 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 |
| \f[R] |
| .fi |
| .SH INCLUDE A TIME STAMP FOR EACH SAMPLE |
| .PP |
| This example attaches to lvmid 21891 and takes 3 samples at 250 |
| millisecond intervals. |
| The \f[V]-t\f[R] option is used to generate a time stamp for each sample |
| in the first column. |
| .PP |
| The Timestamp column reports the elapsed time in seconds since the start |
| of the target JVM. |
| In addition, the \f[V]-gcoldcapacity\f[R] output shows the old |
| generation capacity (OGC) and the old space capacity (OC) increasing 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 capacity of the generation (and space) is 60,544 KB (OGCMX), |
| so it still has room to expand. |
| .IP |
| .nf |
| \f[CB] |
| 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 |
| \f[R] |
| .fi |
| .SH MONITOR INSTRUMENTATION FOR A REMOTE JVM |
| .PP |
| This example attaches to lvmid 40496 on the system named |
| \f[V]remote.domain\f[R] using the \f[V]-gcutil\f[R] option, with samples |
| taken every second indefinitely. |
| .PP |
| The lvmid is combined with the name of the remote host to construct a |
| vmid of \f[V]40496\[at]remote.domain\f[R]. |
| This vmid results in the use of the \f[V]rmi\f[R] protocol to |
| communicate to the default \f[V]jstatd\f[R] server on the remote host. |
| The \f[V]jstatd\f[R] server is located using the \f[V]rmiregistry\f[R] |
| command on \f[V]remote.domain\f[R] that\[aq]s bound to the default port |
| of the \f[V]rmiregistry\f[R] command (port 1099). |
| .IP |
| .nf |
| \f[CB] |
| jstat -gcutil 40496\[at]remote.domain 1000 |
| \&... output omitted |
| \f[R] |
| .fi |
