GNU/Linux |
CentOS 5.3 |
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jstat(1) |
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jstat
jstat
NAME
SYNOPSIS
PARAMETERS
DESCRIPTION
OPTIONS
This section presents some examples of monitoring a local JVM with alvmid of 21891.Using the gcutil optionThis example attaches to lvmid 21891 and takes 7 samples at 250millisecond intervals and displays the output as specified by the−gcutil option.jstat −gcutil 21891 250 7S0 S1 E O P YGC YGCT FGC FGCT GCT12.44 0.00 27.20 9.49 96.70 78 0.176 5 0.495 0.67212.44 0.00 62.16 9.49 96.70 78 0.176 5 0.495 0.67212.44 0.00 83.97 9.49 96.70 78 0.176 5 0.495 0.6720.00 7.74 0.00 9.51 96.70 79 0.177 5 0.495 0.6730.00 7.74 23.37 9.51 96.70 79 0.177 5 0.495 0.6730.00 7.74 43.82 9.51 96.70 79 0.177 5 0.495 0.6730.00 7.74 58.11 9.51 96.71 79 0.177 5 0.495 0.673The output of this example shows that a young generation collectionoccurred between the 3rd and 4th sample. The collection took 0.001seconds and promoted objects from the eden space (E) to the old space(O), resulting in an increase of old space utilization from 9.49% to9.51%. Before the collection, the survivor space was 12.44% utilized,but after this collection it is only 7.74% utilized.Repeating the column headerstringThis example attaches to lvmid 21891 and takes samples at 250millisecond intervals and displays the output as specified by −gcutiloption. In addition, it uses the −h3 option to output the column headerafter every 3 lines of data.jstat −gcnew −h3 21891 250S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT64.0 64.0 0.0 31.7 31 31 32.0 512.0 178.6 249 0.20364.0 64.0 0.0 31.7 31 31 32.0 512.0 355.5 249 0.20364.0 64.0 35.4 0.0 2 31 32.0 512.0 21.9 250 0.204S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT64.0 64.0 35.4 0.0 2 31 32.0 512.0 245.9 250 0.20464.0 64.0 35.4 0.0 2 31 32.0 512.0 421.1 250 0.20464.0 64.0 0.0 19.0 31 31 32.0 512.0 84.4 251 0.204S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT64.0 64.0 0.0 19.0 31 31 32.0 512.0 306.7 251 0.204In addition to showing the repeating header string, this example showsthat between the 2nd and 3rd samples, a young GC occurred. Its durationwas 0.001 seconds. The collection found enough live data that thesurvivor space 0 utilization (S0U) would would have exceeded thedesired survivor Size (DSS). As a result, objects were promoted to theold 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. Thiscollection found very few survivors and returned the tenuring thresholdto 31.Including atime stamp for each sampleThis example attaches to lvmid 21891 and takes 3 samples at 250millisecond intervals. The −t option is used to generate a time stampfor each sample in the first column.jstat −gcoldcapacity −t 21891 250 3Timestamp OGCMN OGCMX OGC OC YGC FGC FGCT GCT150.1 1408.0 60544.0 11696.0 11696.0 194 80 2.874 3.799150.4 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863150.7 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863The Timestamp column reports the elapsed time in seconds since thestart of the target JVM. In addition, the −gcoldcapacity output showsthe old generation capacity (OGC) and the old space capacity (OC)increasing as the heap expands to meet allocation and/or promotiondemands. The old generation capacity (OGC) has grown to from 11696 KBto 13820 KB after the 81st Full GC (FGC). The maximum capacity of thegeneration (and space) is 60544 KB (OGCMX), so it still has room toexpand.Monitorinstrumentation for a remote JVMThis example attaches to lvmid 40496 on the system named remote.domainusing the −gcutil option, with samples taken every second indefinitely.jstat −gcutil 40496@remote.domain 1000The lvmid is combined with the name of the remote host to construct avmid of 40496@remote.domain. This vmid results in the use of the rmiprotocol to communicate to the default jstatd server on the remotehost. The jstatd server is located using the rmiregistry onremote.domain that is bound to the default rmiregistry port (port1099).SEE ALSO
NAME
jstat −
Java Virtual Machine Statistics Monitoring Tool
SYNOPSIS
jstat [
generalOption | outputOptionsvmid
[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.
−hn
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.
−tn
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 the following
documents:
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java − the Java application launcher
(Solaris) @ |
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http://java.sun.com/javase/6/docs/technotes/tools/solaris/java.html
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java − the Java
application launcher (Linux) @ |
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http://java.sun.com/javase/6/docs/technotes/tools/linux/java.html
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java − the Java
application launcher (Windows) |
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STATOPTIONS
AND
OUTPUT
The following
tables summarize the columns that jstat outputs for
each statOption.
−class
Option
−compiler
Option
−gc
Option
−gccapacity
Option
−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:
−gcnew
Option
−gcnewcapacity
Option
−gcold
Option
−gcoldcapacity
Option
−gcpermcapacity
Option
−gcutil
Option
−printcompilation
Option
This section presents some examples of monitoring a local JVM with alvmid of 21891.Using the gcutil optionThis example attaches to lvmid 21891 and takes 7 samples at 250millisecond intervals and displays the output as specified by the−gcutil option.jstat −gcutil 21891 250 7S0 S1 E O P YGC YGCT FGC FGCT GCT12.44 0.00 27.20 9.49 96.70 78 0.176 5 0.495 0.67212.44 0.00 62.16 9.49 96.70 78 0.176 5 0.495 0.67212.44 0.00 83.97 9.49 96.70 78 0.176 5 0.495 0.6720.00 7.74 0.00 9.51 96.70 79 0.177 5 0.495 0.6730.00 7.74 23.37 9.51 96.70 79 0.177 5 0.495 0.6730.00 7.74 43.82 9.51 96.70 79 0.177 5 0.495 0.6730.00 7.74 58.11 9.51 96.71 79 0.177 5 0.495 0.673The output of this example shows that a young generation collectionoccurred between the 3rd and 4th sample. The collection took 0.001seconds and promoted objects from the eden space (E) to the old space(O), resulting in an increase of old space utilization from 9.49% to9.51%. Before the collection, the survivor space was 12.44% utilized,but after this collection it is only 7.74% utilized.Repeating the column headerstringThis example attaches to lvmid 21891 and takes samples at 250millisecond intervals and displays the output as specified by −gcutiloption. In addition, it uses the −h3 option to output the column headerafter every 3 lines of data.jstat −gcnew −h3 21891 250S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT64.0 64.0 0.0 31.7 31 31 32.0 512.0 178.6 249 0.20364.0 64.0 0.0 31.7 31 31 32.0 512.0 355.5 249 0.20364.0 64.0 35.4 0.0 2 31 32.0 512.0 21.9 250 0.204S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT64.0 64.0 35.4 0.0 2 31 32.0 512.0 245.9 250 0.20464.0 64.0 35.4 0.0 2 31 32.0 512.0 421.1 250 0.20464.0 64.0 0.0 19.0 31 31 32.0 512.0 84.4 251 0.204S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT64.0 64.0 0.0 19.0 31 31 32.0 512.0 306.7 251 0.204In addition to showing the repeating header string, this example showsthat between the 2nd and 3rd samples, a young GC occurred. Its durationwas 0.001 seconds. The collection found enough live data that thesurvivor space 0 utilization (S0U) would would have exceeded thedesired survivor Size (DSS). As a result, objects were promoted to theold 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. Thiscollection found very few survivors and returned the tenuring thresholdto 31.Including atime stamp for each sampleThis example attaches to lvmid 21891 and takes 3 samples at 250millisecond intervals. The −t option is used to generate a time stampfor each sample in the first column.jstat −gcoldcapacity −t 21891 250 3Timestamp OGCMN OGCMX OGC OC YGC FGC FGCT GCT150.1 1408.0 60544.0 11696.0 11696.0 194 80 2.874 3.799150.4 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863150.7 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863The Timestamp column reports the elapsed time in seconds since thestart of the target JVM. In addition, the −gcoldcapacity output showsthe old generation capacity (OGC) and the old space capacity (OC)increasing as the heap expands to meet allocation and/or promotiondemands. The old generation capacity (OGC) has grown to from 11696 KBto 13820 KB after the 81st Full GC (FGC). The maximum capacity of thegeneration (and space) is 60544 KB (OGCMX), so it still has room toexpand.Monitorinstrumentation for a remote JVMThis example attaches to lvmid 40496 on the system named remote.domainusing the −gcutil option, with samples taken every second indefinitely.jstat −gcutil 40496@remote.domain 1000The lvmid is combined with the name of the remote host to construct avmid of 40496@remote.domain. This vmid results in the use of the rmiprotocol to communicate to the default jstatd server on the remotehost. The jstatd server is located using the rmiregistry onremote.domain that is bound to the default rmiregistry port (port1099).SEE ALSO
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java − the Java
Application Launcher |
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jps − the Java Process Status Application |
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jstatd − the jvmstat daemon |
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rmiregistry − the Java Remote Object Registry |
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jstat(1) |
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