669 lines
22 KiB
Groff
Executable File
669 lines
22 KiB
Groff
Executable File
.\" Automatically generated by Pandoc 2.19.2
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.\"
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.\" Define V font for inline verbatim, using C font in formats
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.\" that render this, and otherwise B font.
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.\}
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.TH "JSTAT" "1" "2025" "JDK 24.0.2" "JDK Commands"
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.hy
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.SH NAME
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.PP
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jstat - monitor JVM statistics
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.SH SYNOPSIS
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.PP
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\f[B]Note:\f[R] This command is experimental and unsupported.
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.PP
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\f[V]jstat\f[R] \f[I]generalOptions\f[R]
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.PP
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\f[V]jstat\f[R] \f[I]outputOptions\f[R] [\f[V]-t\f[R]] [\f[V]-h\f[R]
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\f[I]lines\f[R]] \f[I]vmid\f[R] [\f[I]interval\f[R] [\f[I]count\f[R]]]
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.TP
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\f[I]generalOptions\f[R]
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A single general command-line option.
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See \f[B]General Options\f[R].
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.TP
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\f[I]outputOptions\f[R]
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An option reported by the \f[V]-options\f[R] option.
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|
One or more output options that consist of a single
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|
\f[V]statOption\f[R], plus any of the \f[V]-t\f[R], \f[V]-h\f[R], and
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\f[V]-J\f[R] options.
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|
See \f[B]Output Options for the jstat Command\f[R].
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.TP
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\f[V]-t\f[R]
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|
Displays a time-stamp column as the first column of output.
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The time stamp is the time since the start time of the target JVM.
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.TP
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\f[V]-h\f[R] \f[I]n\f[R]
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Displays a column header every \f[I]n\f[R] samples (output rows), where
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\f[I]n\f[R] is a positive integer.
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The default value is \f[V]0\f[R], which displays the column header of
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the first row of data.
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.TP
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\f[I]vmid\f[R]
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|
A virtual machine identifier, which is a string that indicates the
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target JVM.
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|
See \f[B]Virtual Machine Identifier\f[R].
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.TP
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|
\f[I]interval\f[R]
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|
The sampling interval in the specified units, seconds (s) or
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|
milliseconds (ms).
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|
Default units are milliseconds.
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|
This must be a positive integer.
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When specified, the \f[V]jstat\f[R] command produces its output at each
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interval.
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.TP
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\f[I]count\f[R]
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The number of samples to display.
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The default value is infinity, which causes the \f[V]jstat\f[R] command
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to display statistics until the target JVM terminates or the
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\f[V]jstat\f[R] command is terminated.
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This value must be a positive integer.
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.SH DESCRIPTION
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.PP
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The \f[V]jstat\f[R] command displays performance statistics for an
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instrumented Java HotSpot VM.
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The target JVM is identified by its virtual machine identifier, or
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\f[V]vmid\f[R] option.
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.PP
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The \f[V]jstat\f[R] command supports two types of options, general
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options and output options.
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|
General options cause the \f[V]jstat\f[R] command to display simple
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usage and version information.
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|
Output options determine the content and format of the statistical
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output.
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.PP
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All options and their functionality are subject to change or removal in
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future releases.
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.SH GENERAL OPTIONS
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.PP
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|
If you specify one of the general options, then you can\[aq]t specify
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any other option or parameter.
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.TP
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\f[V]-help\f[R]
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|
Displays a help message.
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.TP
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\f[V]-options\f[R]
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|
Displays a list of static options.
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|
See \f[B]Output Options for the jstat Command\f[R].
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|
.SH OUTPUT OPTIONS FOR THE JSTAT COMMAND
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.PP
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|
If you don\[aq]t specify a general option, then you can specify output
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|
options.
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|
Output options determine the content and format of the \f[V]jstat\f[R]
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|
command\[aq]s output, and consist of a single \f[V]statOption\f[R], plus
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any of the other output options (\f[V]-h\f[R], \f[V]-t\f[R], and
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|
\f[V]-J\f[R]).
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|
The \f[V]statOption\f[R] must come first.
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.PP
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|
Output is formatted as a table, with columns that are separated by
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spaces.
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|
A header row with titles describes the columns.
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|
Use the \f[V]-h\f[R] option to set the frequency at which the header is
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displayed.
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|
Column header names are consistent among the different options.
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|
In general, if two options provide a column with the same name, then the
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data source for the two columns is the same.
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|
.PP
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|
Use the \f[V]-t\f[R] option to display a time-stamp column, labeled
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|
Timestamp as the first column of output.
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|
The Timestamp column contains the elapsed time, in seconds, since the
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|
target JVM started.
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|
The resolution of the time stamp is dependent on various factors and is
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|
subject to variation due to delayed thread scheduling on heavily loaded
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systems.
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.PP
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Use the interval and count parameters to determine how frequently and
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|
how many times, respectively, the \f[V]jstat\f[R] command displays its
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|
output.
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.PP
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\f[B]Note:\f[R]
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.PP
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Don\[aq]t write scripts to parse the \f[V]jstat\f[R] command\[aq]s
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|
output because the format might change in future releases.
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|
If you write scripts that parse the \f[V]jstat\f[R] command output, then
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|
expect to modify them for future releases of this tool.
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.TP
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|
\f[V]-statOption\f[R]
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|
Determines the statistics information that the \f[V]jstat\f[R] command
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displays.
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|
The following lists the available options.
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|
Use the \f[V]-options\f[R] general option to display the list of options
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|
for a particular platform installation.
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|
See \f[B]Stat Options and Output\f[R].
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.RS
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.PP
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\f[V]class\f[R]: Displays statistics about the behavior of the class
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|
loader.
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.PP
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|
\f[V]compiler\f[R]: Displays statistics about the behavior of the Java
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|
HotSpot VM Just-in-Time compiler.
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.PP
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|
\f[V]gc\f[R]: Displays statistics about the behavior of the garbage
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|
collected heap.
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.PP
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|
\f[V]gccapacity\f[R]: Displays statistics about the capacities of the
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|
generations and their corresponding spaces.
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|
.PP
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|
\f[V]gccause\f[R]: Displays a summary about garbage collection
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|
statistics (same as \f[V]-gcutil\f[R]), with the cause of the last and
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|
current (when applicable) garbage collection events.
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.PP
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|
\f[V]gcnew\f[R]: Displays statistics about the behavior of the new
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|
generation.
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|
.PP
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|
\f[V]gcnewcapacity\f[R]: Displays statistics about the sizes of the new
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|
generations and their corresponding spaces.
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.PP
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|
\f[V]gcold\f[R]: Displays statistics about the behavior of the old
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|
generation and metaspace statistics.
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.PP
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|
\f[V]gcoldcapacity\f[R]: Displays statistics about the sizes of the old
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|
generation.
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.PP
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\f[V]gcmetacapacity\f[R]: Displays statistics about the sizes of the
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|
metaspace.
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.PP
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|
\f[V]gcutil\f[R]: Displays a summary about garbage collection
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|
statistics.
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.PP
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|
\f[V]printcompilation\f[R]: Displays Java HotSpot VM compilation method
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|
statistics.
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.RE
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.TP
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|
\f[V]-J\f[R]\f[I]javaOption\f[R]
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|
Passes \f[I]javaOption\f[R] to the Java application launcher.
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|
For example, \f[V]-J-Xms48m\f[R] sets the startup memory to 48 MB.
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|
For a complete list of options, see \f[B]java\f[R].
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|
.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
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|
\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
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|
\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
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|
operations.
|
|
.RE
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|
.TP
|
|
\f[V]-compiler\f[R] \f[I]option\f[R]
|
|
Java HotSpot VM Just-in-Time compiler statistics.
|
|
.RS
|
|
.PP
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|
\f[V]Compiled\f[R]: Number of compilation tasks performed.
|
|
.PP
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|
\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
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|
\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
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|
\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
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|
.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
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|
.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
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.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
|