1jstat(1) General Commands Manual jstat(1)
2
6 jstat - Java Virtual Machine Statistics Monitoring Tool
7
9 jstat [ generalOption | outputOptionsvmid [interval[s|ms] [count]] ]
10
12 generalOption
13 A single general command-line option (-help, -options, or -version)
14 outputOptions
16 One or more output options, consisting of a single statOption, plus
17 any of the -t, -h, and -J options.
18 vmid
20 Virtual machine identifier, a string indicating the target Java vir‐
21 tual machine (JVM). The general syntax is
22 [protocol:][//]lvmid[@hostname[:port]/servername]
23 The syntax of the vmid string largely corresponds to the syntax of a
24 URI. The vmid can vary from a simple integer representing a local
25 JVM to a more complex construction specifying a communications pro‐
26 tocol, port number, and other implementation-specific values. See
27 Virtual Machine Identifier for details.
28 interval[s|ms]
30 Sampling interval in the specified units, seconds (s) or millisec‐
31 onds (ms). Default units are milliseconds. Must be a positive inte‐
32 ger. If specified, jstat will produce its output at each interval.
33 count
35 Number of samples to display. Default value is infinity; that is,
36 jstat displays statistics until the target JVM terminates or the
37 jstat command is terminated. Must be a positive integer.
38
40 The jstat tool displays performance statistics for an instrumented
41 HotSpot Java virtual machine (JVM). The target JVM is identified by its
42 virtual machine identifier, or vmid option described below.
43 NOTE: This utility is unsupported and may not be available in future
45 versions of the JDK. It is not currently available on Windows 98 and
46 Windows ME. platforms.
47 VIRTUAL MACHINE IDENTIFIER
49 The syntax of the vmid string largely corresponds to the syntax of a
50 URI:
51 [protocol:][//]lvmid[@hostname][:port][/servername]
52 protocol
54 The communications protocol. If the protocol is omitted and a host‐
55 name is not specified, the default protocol is a platform specific
56 optimized local protocol. If the protocol is omitted and a hostname
57 is specified, then the default protocol is rmi.
58 lvmid
60 The local virtual machine identifier for the target JVM. The lvmid
61 is a platform-specific value that uniquely identifies a JVM on a
62 system. The lvmid is the only required component of a virtual
63 machine identifier. The lvmid is typically, but not necessarily, the
64 operating system's process identifier for the target JVM process.
65 You can use the jps command to determine the lvmid. Also, you can
66 determine lvmid on Unix platforms with the ps command, and on Win‐
67 dows with the Windows Task Manager.
68 hostname
70 A hostname or IP address indicating the target host. If hostname is
71 omitted, then the target host is the local host.
72 port
74 The default port for communicating with the remote server. If the
75 hostname is omitted or the protocol specifies an optimized, local
76 protocol, then port is ignored. Otherwise, treatment of the port
77 parameter is implementation specific. For the default rmi protocol,
78 the port indicates the port number for the rmiregistry on the remote
79 host. If port is omitted, and protocol indicates rmi, then the
80 default rmiregistry port (1099) is used.
81 servername
83 The treatment of this parameter depends on implementation. For the
84 optimized local protocol, this field is ignored. For the rmi proto‐
85 col, it represents the name of the RMI remote object on the remote
86 host.
87
89 The jstat command supports two types of options, general options and
90 output options. General options cause jstat to display simple usage and
91 version information. Output options determine the content and format of
92 the statistical output.
93 NOTE: All options, and their functionality are subject to change or
95 removal in future releases.
96 GENERAL
98 OPTIONS
99 If you specify one of the general options, you cannot specify any other
101 option or parameter.
102 -help
104 Display help message.
105 -version
107 Display version information.
108 -options
110 Display list of statistics options. See the Output Options section
111 below.
112 OUTPUT
114 OPTIONS
115 If you do not specify a general option, then you can specify output
117 options. Output options determine the content and format of jstat's
118 output, and consist of a single statOption, plus any of the other out‐
119 put options (-h, -t, and -J). The statOption must come first.
120 Output is formatted as a table, with columns are separated by spaces. A
122 header row with titles describes the columns. Use the -h option to set
123 the frequency at which the header is displayed. Column header names
124 are generally consistent between the different options. In general, if
125 two options provide a column with the same name, then the data source
126 for the two columns are the same.
127 Use the -t option to display a time stamp column, labeled Timestamp as
129 the first column of output. The Timestamp column contains the elapsed
130 time, in seconds, since startup of the target JVM. The resolution of
131 the time stamp is dependent on various factors and is subject to varia‐
132 tion due to delayed thread scheduling on heavily loaded systems.
133 Use the interval and count parameters to determine how frequently and
135 how many times, respectively, jstat displays its output.
136 NOTE: You are advised not to write scripts to parse jstat's output
138 since the format may change in future releases. If you choose to write
139 scripts that parse jstat output, expect to modify them for future
140 releases of this tool.
141 -statOption
143 Determines the statistics information that jstat displays. The fol‐
144 lowing table lists the available options. Use the -options general
145 option to display the list of options for a particular platform
146 installation.
147 -hn
150 Display a column header every n samples (output rows), where n is a
151 positive integer. Default value is 0, which displays the column
152 header above the first row of data.
153 -tn
155 Display a timestamp column as the first column of output. The time‐
156 stamp is the the time since the start time of the target JVM.
157 -JjavaOption
159 Pass javaOption to the java application launcher. For example,
160 -J-Xms48m sets the startup memory to 48 megabytes. For a complete
161 list of options, see the following documents:
162 * java - the Java application launcher (Solaris) @
164 http://java.sun.com/javase/6/docs/tech‐
165 notes/tools/solaris/java.html
166 * java - the Java application launcher (Linux) @
168 http://java.sun.com/javase/6/docs/technotes/tools/linux/java.html
169 * java - the Java application launcher (Windows)
171 STATOPTIONS AND
173 OUTPUT
174 The following tables summarize the columns that jstat outputs for each
176 statOption.
177 -class Option
179 -compiler
180 Option
181 -gc Option
184 -gccapacity Option
185 -gccause
186 Option
187 This option displays the same summary of garbage collection statistics
189 as the -gcutil option, but includes the causes of the last garbage col‐
190 lection event and (if applicable) the current garbage collection event.
191 In addition to the columns listed for -gcutil, this option adds the
192 following columns:
193 -gcnew Option
196 -gcnewcapacity Option
197 -gcold Option
198 -gcoldcapacity Option
199 -gcpermcapacity Option
200 -gcutil
201 Option
202 -printcompilation Option
205 This section presents some examples of monitoring a local JVM with a
207 lvmid of 21891.
208 Using the gcutil option
210 This example attaches to lvmid 21891 and takes 7 samples at 250 mil‐
211 lisecond intervals and displays the output as specified by the -gcutil
212 option.
213 jstat -gcutil 21891 250 7
214 S0 S1 E O P YGC YGCT FGC FGCT GCT
216 12.44 0.00 27.20 9.49 96.70 78 0.176 5 0.495 0.672
218 12.44 0.00 62.16 9.49 96.70 78 0.176 5 0.495 0.672
220 12.44 0.00 83.97 9.49 96.70 78 0.176 5 0.495 0.672
222 0.00 7.74 0.00 9.51 96.70 79 0.177 5 0.495 0.673
224 0.00 7.74 23.37 9.51 96.70 79 0.177 5 0.495 0.673
226 0.00 7.74 43.82 9.51 96.70 79 0.177 5 0.495 0.673
228 0.00 7.74 58.11 9.51 96.71 79 0.177 5 0.495 0.673
230 The output of this example shows that a young generation collection
232 occurred between the 3rd and 4th sample. The collection took 0.001 sec‐
233 onds and promoted objects from the eden space (E) to the old space (O),
234 resulting in an increase of old space utilization from 9.49% to 9.51%.
235 Before the collection, the survivor space was 12.44% utilized, but
236 after this collection it is only 7.74% utilized.
237 Repeating the column header
239 string
240 This example attaches to lvmid 21891 and takes samples at 250 millisec‐
242 ond intervals and displays the output as specified by -gcutil option.
243 In addition, it uses the -h3 option to output the column header after
244 every 3 lines of data.
245 jstat -gcnew -h3 21891 250
246 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
248 64.0 64.0 0.0 31.7 31 31 32.0 512.0 178.6 249 0.203
250 64.0 64.0 0.0 31.7 31 31 32.0 512.0 355.5 249 0.203
252 64.0 64.0 35.4 0.0 2 31 32.0 512.0 21.9 250 0.204
254 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
256 64.0 64.0 35.4 0.0 2 31 32.0 512.0 245.9 250 0.204
258 64.0 64.0 35.4 0.0 2 31 32.0 512.0 421.1 250 0.204
260 64.0 64.0 0.0 19.0 31 31 32.0 512.0 84.4 251 0.204
262 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
264 64.0 64.0 0.0 19.0 31 31 32.0 512.0 306.7 251 0.204
266 In addition to showing the repeating header string, this example shows
268 that between the 2nd and 3rd samples, a young GC occurred. Its duration
269 was 0.001 seconds. The collection found enough live data that the sur‐
270 vivor space 0 utilization (S0U) would would have exceeded the desired
271 survivor Size (DSS). As a result, objects were promoted to the old gen‐
272 eration (not visible in this output), and the tenuring threshold (TT)
273 was lowered from 31 to 2.
274 Another collection occurs between the 5th and 6th samples. This collec‐
276 tion found very few survivors and returned the tenuring threshold to
277 31.
278 Including a
280 time stamp for each sample
281 This example attaches to lvmid 21891 and takes 3 samples at 250 mil‐
283 lisecond intervals. The -t option is used to generate a time stamp for
284 each sample in the first column.
285 jstat -gcoldcapacity -t 21891 250 3
286 Timestamp OGCMN OGCMX OGC OC YGC FGC FGCT GCT
288 150.1 1408.0 60544.0 11696.0 11696.0 194 80 2.874 3.799
290 150.4 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863
292 150.7 1408.0 60544.0 13820.0 13820.0 194 81 2.938 3.863
294 The Timestamp column reports the elapsed time in seconds since the
296 start of the target JVM. In addition, the -gcoldcapacity output shows
297 the old generation capacity (OGC) and the old space capacity (OC)
298 increasing as the heap expands to meet allocation and/or promotion
299 demands. The old generation capacity (OGC) has grown to from 11696 KB
300 to 13820 KB after the 81st Full GC (FGC). The maximum capacity of the
301 generation (and space) is 60544 KB (OGCMX), so it still has room to
302 expand.
303 Monitor
305 instrumentation for a remote JVM
306 This example attaches to lvmid 40496 on the system named remote.domain
308 using the -gcutil option, with samples taken every second indefinitely.
309 jstat -gcutil 40496@remote.domain 1000
310 The lvmid is combined with the name of the remote host to construct a
313 vmid of 40496@remote.domain. This vmid results in the use of the rmi
314 protocol to communicate to the default jstatd server on the remote
315 host. The jstatd server is located using the rmiregistry on
316 remote.domain that is bound to the default rmiregistry port (port
317 1099).
318
320 * java - the Java Application Launcher
321 * jps - the Java Process Status Application
323 * jstatd - the jvmstat daemon
325 * rmiregistry - the Java Remote Object Registry
327 06 Aug 2006 jstat(1)