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rgallardb6435452013-11-25 20:19:02 -08001'\" t
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22.\"
23.\" Title: jstat
24.\" Language: English
25.\" Date: 03 March 2015
26.\" SectDesc: Monitoring Tools
27.\" Software: JDK 8
28.\" Arch: generic
29.\" Part Number: E38207-04
30.\" Doc ID: JSSON
rgallardb6435452013-11-25 20:19:02 -080031.\"
32.if n .pl 99999
rgallardf71f2512015-02-02 10:12:21 -080033.TH "jstat" "1" "03 March 2015" "JDK 8" "Monitoring Tools"
34.\" -----------------------------------------------------------------
35.\" * Define some portability stuff
36.\" -----------------------------------------------------------------
37.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
38.\" http://bugs.debian.org/507673
39.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
40.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
41.ie \n(.g .ds Aq \(aq
42.el .ds Aq '
43.\" -----------------------------------------------------------------
44.\" * set default formatting
45.\" -----------------------------------------------------------------
46.\" disable hyphenation
47.nh
48.\" disable justification (adjust text to left margin only)
49.ad l
50.\" -----------------------------------------------------------------
51.\" * MAIN CONTENT STARTS HERE *
52.\" -----------------------------------------------------------------
53.SH "NAME"
rgallardb6435452013-11-25 20:19:02 -080054jstat \- Monitors Java Virtual Machine (JVM) statistics\&. This command is experimental and unsupported\&.
rgallardf71f2512015-02-02 10:12:21 -080055.SH "SYNOPSIS"
56.sp
57.if n \{\
58.RS 4
59.\}
60.nf
rgallardb6435452013-11-25 20:19:02 -080061\fBjstat\fR [ \fIgeneralOption\fR | \fIoutputOptions vmid\fR [ \fIinterval\fR[s|ms] [ \fIcount \fR] ]
rgallardf71f2512015-02-02 10:12:21 -080062.fi
63.if n \{\
64.RE
65.\}
66.PP
rgallardb6435452013-11-25 20:19:02 -080067\fIgeneralOption\fR
rgallardf71f2512015-02-02 10:12:21 -080068.RS 4
69A single general command\-line option
70\fB\-help\fR
71or
72\fB\-options\fR\&. See General Options\&.
73.RE
74.PP
rgallardb6435452013-11-25 20:19:02 -080075\fIoutputOptions\fR
rgallardf71f2512015-02-02 10:12:21 -080076.RS 4
77One or more output options that consist of a single
78\fBstatOption\fR, plus any of the
79\fB\-t\fR,
80\fB\-h\fR, and
81\fB\-J\fR
82options\&. See Output Options\&.
83.RE
84.PP
rgallardb6435452013-11-25 20:19:02 -080085\fIvmid\fR
rgallardf71f2512015-02-02 10:12:21 -080086.RS 4
rgallardb6435452013-11-25 20:19:02 -080087Virtual machine identifier, which is a string that indicates the target JVM\&. The general syntax is the following:
rgallardf71f2512015-02-02 10:12:21 -080088.sp
89.if n \{\
90.RS 4
91.\}
92.nf
93\fB[protocol:][//]lvmid[@hostname[:port]/servername]\fR
94
95.fi
96.if n \{\
97.RE
98.\}
99The syntax of the
100\fBvmid\fR
101string corresponds to the syntax of a URI\&. The
102\fBvmid\fR
103string 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\&. See Virtual Machine Identifier\&.
104.RE
105.PP
rgallardb6435452013-11-25 20:19:02 -0800106\fIinterval\fR [s|ms]
rgallardf71f2512015-02-02 10:12:21 -0800107.RS 4
108Sampling interval in the specified units, seconds (s) or milliseconds (ms)\&. Default units are milliseconds\&. Must be a positive integer\&. When specified, the
109\fBjstat\fR
110command produces its output at each interval\&.
111.RE
112.PP
rgallardb6435452013-11-25 20:19:02 -0800113\fIcount\fR
rgallardf71f2512015-02-02 10:12:21 -0800114.RS 4
115Number of samples to display\&. The default value is infinity which causes the
116\fBjstat\fR
117command to display statistics until the target JVM terminates or the
118\fBjstat\fR
119command is terminated\&. This value must be a positive integer\&.
120.RE
121.SH "DESCRIPTION"
122.PP
123The
124\fBjstat\fR
125command displays performance statistics for an instrumented Java HotSpot VM\&. The target JVM is identified by its virtual machine identifier, or
126\fBvmid\fR
127option\&.
128.SH "VIRTUAL MACHINE IDENTIFIER"
129.PP
130The syntax of the
131\fBvmid\fR
132string corresponds to the syntax of a URI:
133.sp
134.if n \{\
135.RS 4
136.\}
137.nf
138\fB[protocol:][//]lvmid[@hostname[:port]/servername]\fR
139
140.fi
141.if n \{\
142.RE
143.\}
144.PP
rgallardb6435452013-11-25 20:19:02 -0800145\fIprotocol\fR
rgallardf71f2512015-02-02 10:12:21 -0800146.RS 4
147The communications protocol\&. If the
148\fIprotocol\fR
149value is omitted and a host name is not specified, then the default protocol is a platform\-specific optimized local protocol\&. If the
150\fIprotocol\fR
151value is omitted and a host name is specified, then the default protocol is
152\fBrmi\fR\&.
153.RE
154.PP
rgallardb6435452013-11-25 20:19:02 -0800155\fIlvmid\fR
rgallardf71f2512015-02-02 10:12:21 -0800156.RS 4
157The local virtual machine identifier for the target JVM\&. The
158\fBlvmid\fR
159is a platform\-specific value that uniquely identifies a JVM on a system\&. The
160\fBlvmid\fR
161is the only required component of a virtual machine identifier\&. The
162\fBlvmid\fR
163is typically, but not necessarily, the operating system\*(Aqs process identifier for the target JVM process\&. You can use the
164\fBjps\fR
165command to determine the
166\fBlvmid\fR\&. Also, you can determine the
167\fBlvmid\fR
168on Solaris, Linux, and OS X platforms with the
169\fBps\fR
170command, and on Windows with the Windows Task Manager\&.
171.RE
172.PP
rgallardb6435452013-11-25 20:19:02 -0800173\fIhostname\fR
rgallardf71f2512015-02-02 10:12:21 -0800174.RS 4
175A hostname or IP address that indicates the target host\&. If the
176\fIhostname\fR
177value is omitted, then the target host is the local host\&.
178.RE
179.PP
rgallardb6435452013-11-25 20:19:02 -0800180\fIport\fR
rgallardf71f2512015-02-02 10:12:21 -0800181.RS 4
182The default port for communicating with the remote server\&. If the
183\fIhostname\fR
184value is omitted or the
185\fIprotocol\fR
186value specifies an optimized, local protocol, then the
187\fIport\fR
188value is ignored\&. Otherwise, treatment of the
189\fBport\fR
190parameter is implementation\-specific\&. For the default
191\fBrmi\fR
192protocol, the port value indicates the port number for the rmiregistry on the remote host\&. If the
193\fIport\fR
194value is omitted and the
195\fIprotocol\fR
196value indicates
197\fBrmi\fR, then the default rmiregistry port (1099) is used\&.
198.RE
199.PP
rgallardb6435452013-11-25 20:19:02 -0800200\fIservername\fR
rgallardf71f2512015-02-02 10:12:21 -0800201.RS 4
202The treatment of the
203\fBservername\fR
204parameter depends on implementation\&. For the optimized local protocol, this field is ignored\&. For the
205\fBrmi\fR
206protocol, it represents the name of the RMI remote object on the remote host\&.
207.RE
208.SH "OPTIONS"
209.PP
210The
211\fBjstat\fR
212command supports two types of options, general options and output options\&. General options cause the
213\fBjstat\fR
214command to display simple usage and version information\&. Output options determine the content and format of the statistical output\&.
rgallardb6435452013-11-25 20:19:02 -0800215.PP
216All options and their functionality are subject to change or removal in future releases\&.
rgallardf71f2512015-02-02 10:12:21 -0800217.SS "General Options"
218.PP
rgallardb6435452013-11-25 20:19:02 -0800219If you specify one of the general options, then you cannot specify any other option or parameter\&.
rgallardf71f2512015-02-02 10:12:21 -0800220.PP
221\-help
222.RS 4
rgallardb6435452013-11-25 20:19:02 -0800223Displays a help message\&.
rgallardf71f2512015-02-02 10:12:21 -0800224.RE
225.PP
226\-options
227.RS 4
rgallardb6435452013-11-25 20:19:02 -0800228Displays a list of static options\&. See Output Options\&.
rgallardf71f2512015-02-02 10:12:21 -0800229.RE
230.SS "Output Options"
rgallardb6435452013-11-25 20:19:02 -0800231.PP
rgallardf71f2512015-02-02 10:12:21 -0800232If you do not specify a general option, then you can specify output options\&. Output options determine the content and format of the
233\fBjstat\fR
234command\*(Aqs output, and consist of a single
235\fBstatOption\fR, plus any of the other output options (\fB\-h\fR,
236\fB\-t\fR, and
237\fB\-J\fR)\&. The
238\fBstatOption\fR
239must come first\&.
rgallardb6435452013-11-25 20:19:02 -0800240.PP
rgallardf71f2512015-02-02 10:12:21 -0800241Output is formatted as a table, with columns that are separated by spaces\&. A header row with titles describes the columns\&. Use the
242\fB\-h\fR
243option 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\&.
rgallardb6435452013-11-25 20:19:02 -0800244.PP
rgallardf71f2512015-02-02 10:12:21 -0800245Use the
246\fB\-t\fR
247option 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\&.
rgallardb6435452013-11-25 20:19:02 -0800248.PP
rgallardf71f2512015-02-02 10:12:21 -0800249Use the interval and count parameters to determine how frequently and how many times, respectively, the
250\fBjstat\fR
251command displays its output\&.
252.PP
253\fBNote:\fR
254Do not to write scripts to parse the
255\fBjstat\fR
256command\*(Aqs output because the format might change in future releases\&. If you write scripts that parse
257\fBjstat\fR
258command output, then expect to modify them for future releases of this tool\&.
259.PP
260\-\fIstatOption\fR
261.RS 4
262Determines the statistics information the
263\fBjstat\fR
264command displays\&. The following lists the available options\&. Use the
265\fB\-options\fR
266general option to display the list of options for a particular platform installation\&. See Stat Options and Output\&.
267.sp
268\fBclass\fR: Displays statistics about the behavior of the class loader\&.
269.sp
270\fBcompiler\fR: Displays statistics about the behavior of the Java HotSpot VM Just\-in\-Time compiler\&.
271.sp
272\fBgc\fR: Displays statistics about the behavior of the garbage collected heap\&.
273.sp
274\fBgccapacity\fR: Displays statistics about the capacities of the generations and their corresponding spaces\&.
275.sp
276\fBgccause\fR: Displays a summary about garbage collection statistics (same as
277\fB\-gcutil\fR), with the cause of the last and current (when applicable) garbage collection events\&.
278.sp
279\fBgcnew\fR: Displays statistics of the behavior of the new generation\&.
280.sp
281\fBgcnewcapacity\fR: Displays statistics about the sizes of the new generations and its corresponding spaces\&.
282.sp
283\fBgcold\fR: Displays statistics about the behavior of the old generation and metaspace statistics\&.
284.sp
285\fBgcoldcapacity\fR: Displays statistics about the sizes of the old generation\&.
286.sp
287\fBgcmetacapacity\fR: Displays statistics about the sizes of the metaspace\&.
288.sp
289\fBgcutil\fR: Displays a summary about garbage collection statistics\&.
290.sp
291\fBprintcompilation\fR: Displays Java HotSpot VM compilation method statistics\&.
292.RE
293.PP
294\-h \fIn\fR
295.RS 4
296Displays a column header every
297\fIn\fR
298samples (output rows), where
299\fIn\fR
300is a positive integer\&. Default value is 0, which displays the column header the first row of data\&.
301.RE
302.PP
303\-t
304.RS 4
rgallard04b0ca42014-10-17 11:33:22 -0700305Displays a timestamp column as the first column of output\&. The time stamp is the time since the start time of the target JVM\&.
rgallardf71f2512015-02-02 10:12:21 -0800306.RE
307.PP
308\-J\fIjavaOption\fR
309.RS 4
310Passes
311\fBjavaOption\fR
312to the Java application launcher\&. For example,
313\fB\-J\-Xms48m\fR
314sets the startup memory to 48 MB\&. For a complete list of options, see
315java(1)\&.
316.RE
317.SS "Stat Options and Output"
318.PP
319The following information summarizes the columns that the
320\fBjstat\fR
321command outputs for each
322\fIstatOption\fR\&.
323.PP
324\-class \fIoption\fR
325.RS 4
rgallardb6435452013-11-25 20:19:02 -0800326Class loader statistics\&.
rgallardf71f2512015-02-02 10:12:21 -0800327.sp
328\fBLoaded\fR: Number of classes loaded\&.
329.sp
330\fBBytes\fR: Number of kBs loaded\&.
331.sp
332\fBUnloaded\fR: Number of classes unloaded\&.
333.sp
334\fBBytes\fR: Number of Kbytes unloaded\&.
335.sp
336\fBTime\fR: Time spent performing class loading and unloading operations\&.
337.RE
338.PP
339\-compiler \fIoption\fR
340.RS 4
341Java HotSpot VM Just\-in\-Time compiler statistics\&.
342.sp
343\fBCompiled\fR: Number of compilation tasks performed\&.
344.sp
345\fBFailed\fR: Number of compilations tasks failed\&.
346.sp
347\fBInvalid\fR: Number of compilation tasks that were invalidated\&.
348.sp
349\fBTime\fR: Time spent performing compilation tasks\&.
350.sp
351\fBFailedType\fR: Compile type of the last failed compilation\&.
352.sp
353\fBFailedMethod\fR: Class name and method of the last failed compilation\&.
354.RE
355.PP
356\-gc \fIoption\fR
357.RS 4
358Garbage\-collected heap statistics\&.
359.sp
360\fBS0C\fR: Current survivor space 0 capacity (kB)\&.
361.sp
362\fBS1C\fR: Current survivor space 1 capacity (kB)\&.
363.sp
364\fBS0U\fR: Survivor space 0 utilization (kB)\&.
365.sp
366\fBS1U\fR: Survivor space 1 utilization (kB)\&.
367.sp
368\fBEC\fR: Current eden space capacity (kB)\&.
369.sp
370\fBEU\fR: Eden space utilization (kB)\&.
371.sp
372\fBOC\fR: Current old space capacity (kB)\&.
373.sp
374\fBOU\fR: Old space utilization (kB)\&.
375.sp
376\fBMC\fR: Metaspace capacity (kB)\&.
377.sp
378\fBMU\fR: Metacspace utilization (kB)\&.
379.sp
380\fBCCSC\fR: Compressed class space capacity (kB)\&.
381.sp
382\fBCCSU\fR: Compressed class space used (kB)\&.
383.sp
384\fBYGC\fR: Number of young generation garbage collection events\&.
385.sp
386\fBYGCT\fR: Young generation garbage collection time\&.
387.sp
388\fBFGC\fR: Number of full GC events\&.
389.sp
390\fBFGCT\fR: Full garbage collection time\&.
391.sp
392\fBGCT\fR: Total garbage collection time\&.
393.RE
394.PP
395\-gccapacity \fIoption\fR
396.RS 4
rgallardb6435452013-11-25 20:19:02 -0800397Memory pool generation and space capacities\&.
rgallardf71f2512015-02-02 10:12:21 -0800398.sp
399\fBNGCMN\fR: Minimum new generation capacity (kB)\&.
400.sp
401\fBNGCMX\fR: Maximum new generation capacity (kB)\&.
402.sp
403\fBNGC\fR: Current new generation capacity (kB)\&.
404.sp
405\fBS0C\fR: Current survivor space 0 capacity (kB)\&.
406.sp
407\fBS1C\fR: Current survivor space 1 capacity (kB)\&.
408.sp
409\fBEC\fR: Current eden space capacity (kB)\&.
410.sp
411\fBOGCMN\fR: Minimum old generation capacity (kB)\&.
412.sp
413\fBOGCMX\fR: Maximum old generation capacity (kB)\&.
414.sp
415\fBOGC\fR: Current old generation capacity (kB)\&.
416.sp
417\fBOC\fR: Current old space capacity (kB)\&.
418.sp
419\fBMCMN\fR: Minimum metaspace capacity (kB)\&.
420.sp
421\fBMCMX\fR: Maximum metaspace capacity (kB)\&.
422.sp
423\fBMC\fR: Metaspace capacity (kB)\&.
424.sp
425\fBCCSMN\fR: Compressed class space minimum capacity (kB)\&.
426.sp
427\fBCCSMX\fR: Compressed class space maximum capacity (kB)\&.
428.sp
429\fBCCSC\fR: Compressed class space capacity (kB)\&.
430.sp
431\fBYGC\fR: Number of young generation GC events\&.
432.sp
433\fBFGC\fR: Number of full GC events\&.
434.RE
435.PP
436\-gccause \fIoption\fR
437.RS 4
438This option displays the same summary of garbage collection statistics as the
439\fB\-gcutil\fR
440option, 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
441\fB\-gcutil\fR, this option adds the following columns\&.
442.sp
443\fBLGCC\fR: Cause of last garbage collection
444.sp
445\fBGCC\fR: Cause of current garbage collection
446.RE
447.PP
448\-gcnew \fIoption\fR
449.RS 4
rgallardb6435452013-11-25 20:19:02 -0800450New generation statistics\&.
rgallardf71f2512015-02-02 10:12:21 -0800451.sp
452\fBS0C\fR: Current survivor space 0 capacity (kB)\&.
453.sp
454\fBS1C\fR: Current survivor space 1 capacity (kB)\&.
455.sp
456\fBS0U\fR: Survivor space 0 utilization (kB)\&.
457.sp
458\fBS1U\fR: Survivor space 1 utilization (kB)\&.
459.sp
460\fBTT\fR: Tenuring threshold\&.
461.sp
462\fBMTT\fR: Maximum tenuring threshold\&.
463.sp
464\fBDSS\fR: Desired survivor size (kB)\&.
465.sp
466\fBEC\fR: Current eden space capacity (kB)\&.
467.sp
468\fBEU\fR: Eden space utilization (kB)\&.
469.sp
470\fBYGC\fR: Number of young generation GC events\&.
471.sp
472\fBYGCT\fR: Young generation garbage collection time\&.
473.RE
474.PP
475\-gcnewcapacity \fIoption\fR
476.RS 4
rgallardb6435452013-11-25 20:19:02 -0800477New generation space size statistics\&.
rgallardf71f2512015-02-02 10:12:21 -0800478.sp
479\fBNGCMN\fR: Minimum new generation capacity (kB)\&.
480.sp
481\fBNGCMX\fR: Maximum new generation capacity (kB)\&.
482.sp
483\fBNGC\fR: Current new generation capacity (kB)\&.
484.sp
485\fBS0CMX\fR: Maximum survivor space 0 capacity (kB)\&.
486.sp
487\fBS0C\fR: Current survivor space 0 capacity (kB)\&.
488.sp
489\fBS1CMX\fR: Maximum survivor space 1 capacity (kB)\&.
490.sp
491\fBS1C\fR: Current survivor space 1 capacity (kB)\&.
492.sp
493\fBECMX\fR: Maximum eden space capacity (kB)\&.
494.sp
495\fBEC\fR: Current eden space capacity (kB)\&.
496.sp
497\fBYGC\fR: Number of young generation GC events\&.
498.sp
499\fBFGC\fR: Number of full GC events\&.
500.RE
501.PP
502\-gcold \fIoption\fR
503.RS 4
504Old generation and metaspace behavior statistics\&.
505.sp
506\fBMC\fR: Metaspace capacity (kB)\&.
507.sp
508\fBMU\fR: Metaspace utilization (kB)\&.
509.sp
510\fBCCSC\fR: Compressed class space capacity (kB)\&.
511.sp
512\fBCCSU\fR: Compressed class space used (kB)\&.
513.sp
514\fBOC\fR: Current old space capacity (kB)\&.
515.sp
516\fBOU\fR: Old space utilization (kB)\&.
517.sp
518\fBYGC\fR: Number of young generation GC events\&.
519.sp
520\fBFGC\fR: Number of full GC events\&.
521.sp
522\fBFGCT\fR: Full garbage collection time\&.
523.sp
524\fBGCT\fR: Total garbage collection time\&.
525.RE
526.PP
527\-gcoldcapacity \fIoption\fR
528.RS 4
529Old generation size statistics\&.
530.sp
531\fBOGCMN\fR: Minimum old generation capacity (kB)\&.
532.sp
533\fBOGCMX\fR: Maximum old generation capacity (kB)\&.
534.sp
535\fBOGC\fR: Current old generation capacity (kB)\&.
536.sp
537\fBOC\fR: Current old space capacity (kB)\&.
538.sp
539\fBYGC\fR: Number of young generation GC events\&.
540.sp
541\fBFGC\fR: Number of full GC events\&.
542.sp
543\fBFGCT\fR: Full garbage collection time\&.
544.sp
545\fBGCT\fR: Total garbage collection time\&.
546.RE
547.PP
548\-gcmetacapacity \fIoption\fR
549.RS 4
550Metaspace size statistics\&.
551.sp
552\fBMCMN\fR: Minimum metaspace capacity (kB)\&.
553.sp
554\fBMCMX\fR: Maximum metaspace capacity (kB)\&.
555.sp
556\fBMC\fR: Metaspace capacity (kB)\&.
557.sp
558\fBCCSMN\fR: Compressed class space minimum capacity (kB)\&.
559.sp
560\fBCCSMX\fR: Compressed class space maximum capacity (kB)\&.
561.sp
562\fBYGC\fR: Number of young generation GC events\&.
563.sp
564\fBFGC\fR: Number of full GC events\&.
565.sp
566\fBFGCT\fR: Full garbage collection time\&.
567.sp
568\fBGCT\fR: Total garbage collection time\&.
569.RE
570.PP
571\-gcutil \fIoption\fR
572.RS 4
rgallardb6435452013-11-25 20:19:02 -0800573Summary of garbage collection statistics\&.
rgallardf71f2512015-02-02 10:12:21 -0800574.sp
575\fBS0\fR: Survivor space 0 utilization as a percentage of the space\*(Aqs current capacity\&.
576.sp
577\fBS1\fR: Survivor space 1 utilization as a percentage of the space\*(Aqs current capacity\&.
578.sp
579\fBE\fR: Eden space utilization as a percentage of the space\*(Aqs current capacity\&.
580.sp
581\fBO\fR: Old space utilization as a percentage of the space\*(Aqs current capacity\&.
582.sp
583\fBM\fR: Metaspace utilization as a percentage of the space\*(Aqs current capacity\&.
584.sp
585\fBCCS\fR: Compressed class space utilization as a percentage\&.
586.sp
587\fBYGC\fR: Number of young generation GC events\&.
588.sp
589\fBYGCT\fR: Young generation garbage collection time\&.
590.sp
591\fBFGC\fR: Number of full GC events\&.
592.sp
593\fBFGCT\fR: Full garbage collection time\&.
594.sp
595\fBGCT\fR: Total garbage collection time\&.
596.RE
597.PP
598\-printcompilation \fIoption\fR
599.RS 4
rgallardb6435452013-11-25 20:19:02 -0800600Java HotSpot VM compiler method statistics\&.
rgallardf71f2512015-02-02 10:12:21 -0800601.sp
602\fBCompiled\fR: Number of compilation tasks performed by the most recently compiled method\&.
603.sp
604\fBSize\fR: Number of bytes of byte code of the most recently compiled method\&.
605.sp
606\fBType\fR: Compilation type of the most recently compiled method\&.
607.sp
608\fBMethod\fR: Class name and method name identifying the most recently compiled method\&. Class name uses slash (/) instead of dot (\&.) as a name space separator\&. Method name is the method within the specified class\&. The format for these two fields is consistent with the HotSpot
609\fB\-XX:+PrintCompilation\fR
610option\&.
611.RE
612.SH "EXAMPLES"
613.PP
614This section presents some examples of monitoring a local JVM with an
615\fIlvmid\fR
616of 21891\&.
617.SS "The gcutil Option"
618.PP
619This example attaches to lvmid 21891 and takes 7 samples at 250 millisecond intervals and displays the output as specified by the \-\fBgcutil\fR
620option\&.
rgallardb6435452013-11-25 20:19:02 -0800621.PP
rgallard04b0ca42014-10-17 11:33:22 -0700622The 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 is 91\&.03% utilized\&.
rgallardf71f2512015-02-02 10:12:21 -0800623.sp
624.if n \{\
625.RS 4
626.\}
627.nf
628\fBjstat \-gcutil 21891 250 7\fR
629\fB S0 S1 E O M CCS YGC YGCT FGC FGCT GCT \fR
630\fB 0\&.00 97\&.02 70\&.31 66\&.80 95\&.52 89\&.14 7 0\&.300 0 0\&.000 0\&.300\fR
631\fB 0\&.00 97\&.02 86\&.23 66\&.80 95\&.52 89\&.14 7 0\&.300 0 0\&.000 0\&.300\fR
632\fB 0\&.00 97\&.02 96\&.53 66\&.80 95\&.52 89\&.14 7 0\&.300 0 0\&.000 0\&.300\fR
633\fB 91\&.03 0\&.00 1\&.98 68\&.19 95\&.89 91\&.24 8 0\&.378 0 0\&.000 0\&.378\fR
634\fB 91\&.03 0\&.00 15\&.82 68\&.19 95\&.89 91\&.24 8 0\&.378 0 0\&.000 0\&.378\fR
635\fB 91\&.03 0\&.00 17\&.80 68\&.19 95\&.89 91\&.24 8 0\&.378 0 0\&.000 0\&.378\fR
636\fB 91\&.03 0\&.00 17\&.80 68\&.19 95\&.89 91\&.24 8 0\&.378 0 0\&.000 0\&.378\fR
637.fi
638.if n \{\
639.RE
640.\}
641.SS "Repeat the Column Header String"
642.PP
643This example attaches to lvmid 21891 and takes samples at 250 millisecond intervals and displays the output as specified by
644\fB\-gcnew\fR
645option\&. In addition, it uses the
646\fB\-h3\fR
647option to output the column header after every 3 lines of data\&.
rgallardb6435452013-11-25 20:19:02 -0800648.PP
649In 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\&.
650.PP
651Another collection occurs between the fifth and sixth samples\&. This collection found very few survivors and returned the tenuring threshold to 31\&.
rgallardf71f2512015-02-02 10:12:21 -0800652.sp
653.if n \{\
654.RS 4
655.\}
656.nf
657\fBjstat \-gcnew \-h3 21891 250\fR
658\fB S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT\fR
659\fB 64\&.0 64\&.0 0\&.0 31\&.7 31 31 32\&.0 512\&.0 178\&.6 249 0\&.203\fR
660\fB 64\&.0 64\&.0 0\&.0 31\&.7 31 31 32\&.0 512\&.0 355\&.5 249 0\&.203\fR
661\fB 64\&.0 64\&.0 35\&.4 0\&.0 2 31 32\&.0 512\&.0 21\&.9 250 0\&.204\fR
662\fB S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT\fR
663\fB 64\&.0 64\&.0 35\&.4 0\&.0 2 31 32\&.0 512\&.0 245\&.9 250 0\&.204\fR
664\fB 64\&.0 64\&.0 35\&.4 0\&.0 2 31 32\&.0 512\&.0 421\&.1 250 0\&.204\fR
665\fB 64\&.0 64\&.0 0\&.0 19\&.0 31 31 32\&.0 512\&.0 84\&.4 251 0\&.204\fR
666\fB S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT\fR
667\fB 64\&.0 64\&.0 0\&.0 19\&.0 31 31 32\&.0 512\&.0 306\&.7 251 0\&.204\fR
668
669.fi
670.if n \{\
671.RE
672.\}
673.SS "Include a Time Stamp for Each Sample"
rgallardb6435452013-11-25 20:19:02 -0800674.PP
rgallardf71f2512015-02-02 10:12:21 -0800675This example attaches to lvmid 21891 and takes 3 samples at 250 millisecond intervals\&. The
676\fB\-t\fR
677option is used to generate a time stamp for each sample in the first column\&.
rgallardb6435452013-11-25 20:19:02 -0800678.PP
rgallardf71f2512015-02-02 10:12:21 -0800679The Timestamp column reports the elapsed time in seconds since the start of the target JVM\&. In addition, the
680\fB\-gcoldcapacity\fR
681output 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\&.
682.sp
683.if n \{\
684.RS 4
685.\}
686.nf
687\fBTimestamp OGCMN OGCMX OGC OC YGC FGC FGCT GCT\fR
688\fB 150\&.1 1408\&.0 60544\&.0 11696\&.0 11696\&.0 194 80 2\&.874 3\&.799\fR
689\fB 150\&.4 1408\&.0 60544\&.0 13820\&.0 13820\&.0 194 81 2\&.938 3\&.863\fR
690\fB 150\&.7 1408\&.0 60544\&.0 13820\&.0 13820\&.0 194 81 2\&.938 3\&.863\fR
691
692.fi
693.if n \{\
694.RE
695.\}
696.SS "Monitor Instrumentation for a Remote JVM"
697.PP
698This example attaches to lvmid 40496 on the system named remote\&.domain using the
699\fB\-gcutil\fR
700option, with samples taken every second indefinitely\&.
701.PP
702The lvmid is combined with the name of the remote host to construct a
703\fIvmid\fR
704of
705\fB40496@remote\&.domain\fR\&. This vmid results in the use of the
706\fBrmi\fR
707protocol to communicate to the default
708\fBjstatd\fR
709server on the remote host\&. The
710\fBjstatd\fR
711server is located using the
712\fBrmiregistry\fR
713command on
714\fBremote\&.domain\fR
715that is bound to the default port of the
716\fBrmiregistry\fR
717command (port 1099)\&.
718.sp
719.if n \{\
720.RS 4
721.\}
722.nf
723\fBjstat \-gcutil 40496@remote\&.domain 1000\fR
724\fB\fI\&.\&.\&. output omitted\fR\fR
725
726.fi
727.if n \{\
728.RE
729.\}
730.SH "SEE ALSO"
731.sp
732.RS 4
733.ie n \{\
734\h'-04'\(bu\h'+03'\c
735.\}
736.el \{\
737.sp -1
738.IP \(bu 2.3
739.\}
rgallardb6435452013-11-25 20:19:02 -0800740java(1)
rgallardf71f2512015-02-02 10:12:21 -0800741.RE
742.sp
743.RS 4
744.ie n \{\
745\h'-04'\(bu\h'+03'\c
746.\}
747.el \{\
748.sp -1
749.IP \(bu 2.3
750.\}
rgallardb6435452013-11-25 20:19:02 -0800751jps(1)
rgallardf71f2512015-02-02 10:12:21 -0800752.RE
753.sp
754.RS 4
755.ie n \{\
756\h'-04'\(bu\h'+03'\c
757.\}
758.el \{\
759.sp -1
760.IP \(bu 2.3
761.\}
rgallardb6435452013-11-25 20:19:02 -0800762jstatd(1)
rgallardf71f2512015-02-02 10:12:21 -0800763.RE
764.sp
765.RS 4
766.ie n \{\
767\h'-04'\(bu\h'+03'\c
768.\}
769.el \{\
770.sp -1
771.IP \(bu 2.3
772.\}
rgallardb6435452013-11-25 20:19:02 -0800773rmiregistry(1)
rgallardf71f2512015-02-02 10:12:21 -0800774.RE
775.br
776'pl 8.5i
777'bp