Name¶
jstat - Java Virtual Machine Statistics Monitoring Tool
SYNOPSIS¶
jstat [ generalOption | outputOptions vmid [interval[s|ms] [count]] ]
PARAMETERS¶
- generalOption
- A single general command-line option (-help, -options, or -version)
- outputOptions
- One or more output options, consisting of a single statOption, plus
any of the -t, -h, and -J options.
- vmid
- Virtual machine identifier, a string indicating the target Java virtual
machine (JVM). The general syntax is
[protocol:][//]lvmid[@hostname[:port]/servername]
The syntax of the vmid string largely corresponds to the syntax of a URI.
The vmid can vary from a simple integer representing a local JVM to
a more complex construction specifying a communications protocol, port
number, and other implementation-specific values. See Virtual Machine
Identifier for details.
- interval[s|ms]
- Sampling interval in the specified units, seconds (s) or milliseconds
(ms). Default units are milliseconds. Must be a positive integer. If
specified, jstat will produce its output at each interval.
- count
- Number of samples to display. Default value is infinity; that is,
jstat displays statistics until the target JVM terminates or the
jstat command is terminated. Must be a positive integer.
DESCRIPTION¶
The jstat tool displays performance statistics for an
instrumented HotSpot Java virtual machine (JVM). The target JVM is
identified by its virtual machine identifier, or vmid option
described below.
NOTE: This utility is unsupported and may not be available
in future versions of the JDK. It is not currently available on Windows 98
and Windows ME. platforms.
VIRTUAL MACHINE IDENTIFIER¶
The syntax of the vmid string largely corresponds to the
syntax of a URI:
[protocol:][//]lvmid[@hostname][:port][/servername]
- protocol
- The communications protocol. If the protocol is omitted and a
hostname is not specified, the default protocol is a platform
specific optimized local protocol. If the protocol is omitted and a
hostname is specified, then the default protocol is
rmi.
- lvmid
- The local virtual machine identifier for the target JVM. The lvmid
is a platform-specific value that uniquely identifies a JVM on a system.
The lvmid is the only required component of a virtual machine
identifier. The lvmid is typically, but not necessarily, the
operating system's process identifier for the target JVM process. You can
use the jps(1) 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.
| 0 |
| Statistics of
the behavior of the HotSpot Just\-in\-Time compiler. |
| 0u |
| 0 |
| Statistics of
the behavior of the garbage collected heap. |
| 0u |
| 0 |
| Statistics of
the capacities of the generations and their corresponding spaces. |
| 0u |
| 0 |
| Summary of
garbage collection statistics (same as \f3\-gcutil\fP), with the cause of
the last and current (if applicable) garbage collection events. |
| 0u |
| 0 |
| Statistics of
the behavior of the new generation. |
| 0u |
| 0 |
| Statistics of
the sizes of the new generations and its corresponding spaces. |
| 0u |
| 0 |
| Statistics of
the behavior of the old and permanent generations. |
| 0u |
| 0 |
| Statistics of
the sizes of the old generation. |
| 0u |
| 0 |
| Statistics of
the sizes of the permanent generation. |
| 0u |
| 0 |
| Summary of
garbage collection statistics. |
| 0u |
| 0 |
| HotSpot
compilation method statistics. |
| 0u |
| ?compiler????? |
| +456u |
| -456u |
| ?gccapacity????? |
| +456u |
| -456u |
| ?gccause????? |
| +456u |
| -456u |
| ?gcnewcapacity????? |
| +456u |
| -456u |
| ?gcoldcapacity????? |
| +456u |
| -456u |
| ?gcpermcapacity????? |
| +456u |
| -456u |
| ?printcompilation????? |
| +456u |
| -456u |
| 0u |
- -h n
-
Display a column header every n samples (output rows), where n is a positive integer. Default value is 0, which displays the column header above the first row of data.
- -t n
-
Display a timestamp column as the first column of output. The timestamp is the time since the start time of the target JVM.
- -JjavaOption
-
Pass javaOption to the java application launcher. For example, -J-Xms48m sets the startup memory to 48 megabytes. For a complete list of options, see java(1)
STATOPTIONS AND OUTPUT¶
The following tables summarize the columns that jstat
outputs for each statOption.
-class Option¶
| 0 |
| Number of Kbytes
unloaded. |
| 0u |
| 0 |
| Time spent performing class load and
unload
operations. |
| 0u |
| ?Class Loader
Statistics????? |
| ?Loaded???Number of classes
loaded.?? |
| ?Bytes???Number of Kbytes
loaded.?? |
| ?Unloaded????? |
| +624u |
| -624u |
| ?Time????? |
| +624u |
| -624u |
| 0u |
-compiler Option¶
| 0 |
| Number of compilation tasks that
failed. |
| 0u |
| 0 |
| Number of compilation tasks that were
invalidated. |
| 0u |
| 0 |
| Time spent performing compilation
tasks. |
| 0u |
| 0 |
| Compile type of the last failed
compilation. |
| 0u |
| 0 |
| Class name and method for the last failed
compilation. |
| 0u |
| ?HotSpot Just-In-Time Compiler
Statistics????? |
| ?Compiled????? |
| +1032u |
| -1032u |
| ?Failed????? |
| +1032u |
| -1032u |
| ?Invalid????? |
| +1032u |
| -1032u |
| ?FailedType????? |
| +1032u |
| -1032u |
| ?FailedMethod????? |
| +1032u |
| -1032u |
| 0u |
-gc Option¶
| 0 |
| Current survivor space 1 capacity (KB). |
| 0u |
| 0 |
| Survivor space 0 utilization (KB). |
| 0u |
| 0 |
| Survivor space 1 utilization (KB). |
| 0u |
| 0 |
| Current eden space capacity (KB). |
| 0u |
| 0 |
| Eden space utilization (KB). |
| 0u |
| 0 |
| Current old space capacity (KB). |
| 0u |
| 0 |
| Old space utilization (KB). |
| 0u |
| 0 |
| Current permanent space capacity (KB). |
| 0u |
| 0 |
| Permanent space utilization (KB). |
| 0u |
| 0 |
| Number of young generation GC Events. |
| 0u |
| 0 |
| Young generation garbage collection
time. |
| 0u |
| 0 |
| Full garbage collection time. |
| 0u |
| 0 |
| Total garbage collection time. |
| 0u |
| ?Garbage-collected heap statistics????? |
| ?FGC???Number of full GC events.?? |
-gccapacity Option¶
| 0 |
| Maximum new generation capacity
(KB). |
| 0u |
| 0 |
| Current new generation capacity
(KB). |
| 0u |
| 0 |
| Current survivor space 0 capacity
(KB). |
| 0u |
| 0 |
| Current survivor space 1 capacity
(KB). |
| 0u |
| 0 |
| Current eden space capacity
(KB). |
| 0u |
| 0 |
| Minimum old generation capacity
(KB). |
| 0u |
| 0 |
| Maximum old generation capacity
(KB). |
| 0u |
| 0 |
| Current old generation capacity
(KB). |
| 0u |
| 0 |
| Current old space capacity
(KB). |
| 0u |
| 0 |
| Minimum permanent generation capacity
(KB). |
| 0u |
| 0 |
| Maximum Permanent generation capacity
(KB). |
| 0u |
| 0 |
| Current Permanent generation capacity
(KB). |
| 0u |
| 0 |
| Current Permanent space capacity
(KB). |
| 0u |
| 0 |
| Number of Young generation GC
Events. |
| 0u |
| ?Memory Pool Generation and Space
Capacities????? |
| ?NGCMN????? |
| +1104u |
| -1104u |
| ?NGCMX????? |
| +1104u |
| -1104u |
| ?OGCMN????? |
| +1104u |
| -1104u |
| ?OGCMX????? |
| +1104u |
| -1104u |
| ?PGCMN????? |
| +1104u |
| -1104u |
| ?PGCMX????? |
| +1104u |
| -1104u |
| ?FGC???Number of Full GC
Events.?? |
| 0u |
-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:
| 0 |
| Cause of current Garbage Collection. |
| 0u |
| ?Garbage Collection Statistics, Including GC
Events????? |
| ?GCC????? |
| +1272u |
| -1272u |
| 0u |
-gcnew Option¶
| 0 |
| Current survivor space 1 capacity (KB). |
| 0u |
| 0 |
| Survivor space 0 utilization (KB). |
| 0u |
| 0 |
| Survivor space 1 utilization (KB). |
| 0u |
| 0 |
| Maximum tenuring threshold. |
| 0u |
| 0 |
| Desired survivor size (KB). |
| 0u |
| 0 |
| Current eden space capacity (KB). |
| 0u |
| 0 |
| Eden space utilization (KB). |
| 0u |
| 0 |
| Number of young generation GC events. |
| 0u |
| 0 |
| Young generation garbage collection
time. |
| 0u |
| ?New Generation Statistics????? |
| ?TT???Tenuring threshold.?? |
| ?YGCT????? |
| +672u |
| -672u |
| 0u |
-gcnewcapacity Option¶
| 0 |
| Maximum new generation capacity
(KB). |
| 0u |
| 0 |
| Current new generation capacity
(KB). |
| 0u |
| 0 |
| Maximum survivor space 0 capacity
(KB). |
| 0u |
| 0 |
| Current survivor space 0 capacity
(KB). |
| 0u |
| 0 |
| Maximum survivor space 1 capacity
(KB). |
| 0u |
| 0 |
| Current survivor space 1 capacity
(KB). |
| 0u |
| 0 |
| Maximum eden space capacity
(KB). |
| 0u |
| 0 |
| Current eden space capacity
(KB). |
| 0u |
| 0 |
| Number of young generation GC
events. |
| 0u |
| ?New Generation Space Size
Statistics????? |
| ?FGC???Number of Full GC
Events.?? |
| 0u |
-gcold Option¶
| 0 |
| Permanent space utilization (KB). |
| 0u |
| 0 |
| Current old space capacity (KB). |
| 0u |
| 0 |
| old space utilization (KB). |
| 0u |
| 0 |
| Number of young generation GC events. |
| 0u |
| 0 |
| Full garbage collection time. |
| 0u |
| 0 |
| Total garbage collection time. |
| 0u |
| ?Old and Permanent Generation
Statistics????? |
| ?FGC???Number of full GC events.?? |
| ?GCT????? |
| +1008u |
| -1008u |
| 0u |
-gcoldcapacity Option¶
| 0 |
| Maximum old generation capacity
(KB). |
| 0u |
| 0 |
| Current old generation capacity
(KB). |
| 0u |
| 0 |
| Current old space capacity
(KB). |
| 0u |
| 0 |
| Number of young generation GC
events. |
| 0u |
| 0 |
| Full garbage collection
time. |
| 0u |
| 0 |
| Total garbage collection
time. |
| 0u |
| ?Old Generation
Statistics????? |
| ?FGC???Number of full GC
events.?? |
-gcpermcapacity Option¶
| 0 |
| Maximum permanent generation capacity
(KB). |
| 0u |
| 0 |
| Current permanent generation capacity
(KB). |
| 0u |
| 0 |
| Current permanent space capacity
(KB). |
| 0u |
| 0 |
| Number of young generation GC
events. |
| 0u |
| 0 |
| Full garbage collection
time. |
| 0u |
| 0 |
| Total garbage collection
time. |
| 0u |
| ?Permanent Generation
Statistics????? |
| ?FGC???Number of full GC
events.?? |
-gcutil Option¶
| 0 |
| Survivor space 1 utilization as a
percentage of the space's current capacity. |
| 0u |
| 0 |
| Eden space utilization as a percentage of
the space's current capacity. |
| 0u |
| 0 |
| Old space utilization as a percentage of
the space's current capacity. |
| 0u |
| 0 |
| Permanent space utilization as a
percentage of the space's current capacity. |
| 0u |
| 0 |
| Number of young generation GC
events. |
| 0u |
| 0 |
| Young generation garbage collection
time. |
| 0u |
| 0 |
| Full garbage collection time. |
| 0u |
| 0 |
| Total garbage collection time. |
| 0u |
| ?Summary of Garbage Collection
Statistics????? |
| ?FGC???Number of full GC
events.?? |
| ?GCT????? |
| +1032u |
| -1032u |
| 0u |
-printcompilation Option¶
| 0 |
| Number of bytes of bytecode for the
method. |
| 0u |
| 0 |
| Class name and method name identifying the
compiled method. Class name uses "/" instead of "." as
namespace separator. Method name is the method within the given class. The
format for these two fields is consistent with the HotSpot \-
\f3XX:+PrintComplation\fP
option. |
| 0u |
| ?HotSpot Compiler Method
Statistics????? |
| ?Compiled????? |
| +888u |
| -888u |
| ?Type???Compilation
type.?? |
| ?Method????? |
| +888u |
| -888u |
| 0u |
EXAMPLES¶
This section presents some examples of monitoring a local JVM with
a lvmid of 21891.
Using the gcutil option¶
This example attaches to lvmid 21891 and takes 7 samples at
250 millisecond intervals and displays the output as specified by the
-gcutil option.
jstat -gcutil 21891 250 7
S0 S1 E O P YGC YGCT FGC FGCT GCT
12.44 0.00 27.20 9.49 96.70 78 0.176 5 0.495 0.672
12.44 0.00 62.16 9.49 96.70 78 0.176 5 0.495 0.672
12.44 0.00 83.97 9.49 96.70 78 0.176 5 0.495 0.672
0.00 7.74 0.00 9.51 96.70 79 0.177 5 0.495 0.673
0.00 7.74 23.37 9.51 96.70 79 0.177 5 0.495 0.673
0.00 7.74 43.82 9.51 96.70 79 0.177 5 0.495 0.673
0.00 7.74 58.11 9.51 96.71 79 0.177 5 0.495 0.673
The output of this example shows that a young generation
collection occurred between the 3rd and 4th sample. The collection took
0.001 seconds and promoted objects from the eden space (E) to the old space
(O), resulting in an increase of old space utilization from 9.49% to 9.51%.
Before the collection, the survivor space was 12.44% utilized, but after
this collection it is only 7.74% utilized.
Repeating the column header string¶
This example attaches to lvmid 21891 and takes samples at
250 millisecond intervals and displays the output as specified by
-gcutil option. In addition, it uses the -h3 option to output
the column header after every 3 lines of data.
jstat -gcnew -h3 21891 250
S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
64.0 64.0 0.0 31.7 31 31 32.0 512.0 178.6 249 0.203
64.0 64.0 0.0 31.7 31 31 32.0 512.0 355.5 249 0.203
64.0 64.0 35.4 0.0 2 31 32.0 512.0 21.9 250 0.204
S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
64.0 64.0 35.4 0.0 2 31 32.0 512.0 245.9 250 0.204
64.0 64.0 35.4 0.0 2 31 32.0 512.0 421.1 250 0.204
64.0 64.0 0.0 19.0 31 31 32.0 512.0 84.4 251 0.204
S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
64.0 64.0 0.0 19.0 31 31 32.0 512.0 306.7 251 0.204
In addition to showing the repeating header string, this example
shows that between the 2nd and 3rd samples, a young GC occurred. Its
duration was 0.001 seconds. The collection found enough live data that the
survivor space 0 utilization (S0U) would would have exceeded the desired
survivor Size (DSS). As a result, objects were promoted to the old
generation (not visible in this output), and the tenuring threshold (TT) was
lowered from 31 to 2.
Another collection occurs between the 5th and 6th samples. This
collection found very few survivors and returned the tenuring threshold to
31.
Including a time stamp for each sample¶
This example attaches to lvmid 21891 and takes 3 samples at
250 millisecond intervals. The -t option is used to generate a time
stamp for each sample in the first column.
jstat -gcoldcapacity -t 21891 250 3
Timestamp OGCMN OGCMX OGC OC YGC FGC FGCT GCT
150.1 1408.0 60544.0 11696.0 11696.0 194 80 2.874 3.799
150.4 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863
150.7 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863
The Timestamp column reports the elapsed time in seconds
since the start of the target JVM. In addition, the -gcoldcapacity
output shows the old generation capacity (OGC) and the old space capacity
(OC) increasing as the heap expands to meet allocation and/or promotion
demands. The old generation capacity (OGC) has grown to from 11696 KB to
13820 KB after the 81st Full GC (FGC). The maximum capacity of the
generation (and space) is 60544 KB (OGCMX), so it still has room to
expand.
Monitor instrumentation for a remote JVM¶
This example attaches to lvmid 40496 on the system named
remote.domain using the -gcutil option, with samples taken
every second indefinitely.
jstat -gcutil 40496@remote.domain 1000
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 on remote.domain that is bound to the
default rmiregistry port (port 1099).
SEE ALSO¶
- o
- java(1) - the Java Application Launcher
- o
- jps(1) - the Java Process Status Application
- o
- jstatd(1) - the jvmstat daemon
- o
- rmiregistry(1) - the Java Remote Object Registry