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23
24 title: 'JCMD(1) JDK @@VERSION_SHORT@@ | JDK Commands'
25 date: @@COPYRIGHT_YEAR@@
26 lang: en
27 ---
28
29 ## Name
30
31 jcmd - send diagnostic command requests to a running Java Virtual Machine
32 (JVM)
33
34 ## Synopsis
35
36 `jcmd` \[*pid* \| *main-class*\] *command*... \| `PerfCounter.print` \| `-f`
37 *filename*
38
39 `jcmd` \[`-l`\]
40
41 `jcmd` `-h`
42
43 *pid*
44 : When used, the `jcmd` utility sends the diagnostic command request to the
45 process ID for the Java process.
46
47 *main-class*
48 : When used, the `jcmd` utility sends the diagnostic command request to all
49 Java processes with the specified name of the main class.
50
51 *command*
52 : The `command` must be a valid `jcmd` command for the selected JVM. The list
53 of available commands for `jcmd` is obtained by running the `help` command
54 (`jcmd` *pid* `help`) where *pid* is the process ID for the running Java
55 process.
56
57 `Perfcounter.print`
58 : Prints the performance counters exposed by the specified Java process.
59
60 `-f` *filename*
61 : Reads and executes commands from a specified file, *filename*.
62
63 `-l`
64 : Displays the list of Java Virtual Machine process identifiers that are not
65 running in a separate docker process along with the main class and
66 command-line arguments that were used to launch the process. If the JVM is
67 in a docker process, you must use tools such as `ps` to look up the PID.
68
69 **Note:**
70
71 Using `jcmd` without arguments is the same as using `jcmd -l`.
72
73 `-h`
74 : Displays the `jcmd` utility's command-line help.
75
76 ## Description
77
78 The `jcmd` utility is used to send diagnostic command requests to the JVM. It
79 must be used on the same machine on which the JVM is running, and have the same
80 effective user and group identifiers that were used to launch the JVM. Each
81 diagnostic command has its own set of options and arguments. To display the description,
82 syntax, and a list of available options and arguments for a diagnostic command, use the
83 name of the command as the argument. For example:
84
85 > `jcmd` *pid* `help` *command*
86
87 If arguments contain spaces, then you must surround them with single or double
88 quotation marks (`'` or `"`). In addition, you must escape single or double
89 quotation marks with a backslash (`\`) to prevent the operating system shell
90 from processing quotation marks. Alternatively, you can surround these
91 arguments with single quotation marks and then with double quotation marks (or
92 with double quotation marks and then with single quotation marks).
93
94 If you specify the process identifier (*pid*) or the main class (*main-class*)
95 as the first argument, then the `jcmd` utility sends the diagnostic command
96 request to the Java process with the specified identifier or to all Java
97 processes with the specified name of the main class. You can also send the
98 diagnostic command request to all available Java processes by specifying `0` as
99 the process identifier.
100
101 ## Commands for jcmd
102
103 The *command* must be a valid `jcmd` diagnostic command for the selected JVM.
104 The list of available commands for `jcmd` is obtained by running the `help`
105 command (`jcmd` *pid* `help`) where *pid* is the process ID for a running Java
106 process. If the *pid* is `0`, commands will be sent to all Java processes. The
107 main class argument will be used to match, either partially or fully, the class
108 used to start Java. If no options are given, it lists the running Java process
109 identifiers that are not in separate docker processes along with the main class
110 and command-line arguments that were used to launch the process (the same as
111 using `-l`).
112
113 `jcmd` *commands* may take options and arguments. *Options* are specified using
114 either *key* or *key*`=`*value* syntax. *Arguments* are given as just a value,
115 never name=value.
116
117
118 The following commands are available:
119
120 `help` \[*options*\] \[*arguments*\]
121 : For more information about a specific command.
122
123 *arguments*:
124
125 - *command name*: The name of the command for which we want help (STRING,
126 no default value)
127
128 **Note:**
129
130 The following *options* must be specified using either *key* or
131 *key*`=`*value* syntax.
132
133 *options*:
134
135 - `-all`: (Optional) Show help for all commands (BOOLEAN, false) .
136
137 `Compiler.CodeHeap_Analytics` \[*function*\] \[*granularity*\]
138 : Print CodeHeap analytics
139
140 Impact: Low: Depends on code heap size and content. Holds CodeCache_lock during analysis step, usually sub-second duration.
141
142 *arguments*:
143
144 - *function*: (Optional) Function to be performed (aggregate, UsedSpace, FreeSpace, MethodCount, MethodSpace, MethodAge, MethodNames, discard (STRING, all)
145
146 - *granularity*: (Optional) Detail level - smaller value -> more detail (INT, 4096)
147
148 `Compiler.codecache`
149 : Prints code cache layout and bounds.
150
151 Impact: Low
152
153 `Compiler.codelist`
154 : Prints all compiled methods in code cache that are alive.
155
156 Impact: Medium
157
158 `Compiler.directives_add` *arguments*
159 : Adds compiler directives from a file.
160
161 Impact: Low
162
163 *arguments*:
164
165 - *filename*: The name of the directives file (STRING, no default value)
166
167 `Compiler.directives_clear`
168 : Remove all compiler directives.
169
170 Impact: Low
171
172 `Compiler.directives_print`
173 : Prints all active compiler directives.
174
175 Impact: Low
176
177 `Compiler.directives_remove`
178 : Remove latest added compiler directive.
179
180 Impact: Low
181
182 `Compiler.memory` \[*options*\]
183 : Print compilation footprint
184
185 Impact: Medium: Pause time depends on number of compiled methods
186
187 **Note:**
188
189 The *options* must be specified using either *key* or *key*`=`*value*
190 syntax.
191
192 *options*:
193
194 - `-H`: (Optional) Human readable format (BOOLEAN, false)
195 - `-s`: (Optional) Minimum memory size (MEMORY SIZE, 0)
196
197 `Compiler.perfmap` \[*arguments*\] (Linux only)
198 : Write map file for Linux perf tool.
199
200 Impact: Low
201
202 *arguments*:
203
204 - *filename*: (Optional) The name of the map file. If %p is specified in the filename, it is expanded to the JVM's PID. (FILE, "/tmp/perf-%p.map")
205
206 `Compiler.queue`
207 : Prints methods queued for compilation.
208
209 Impact: Low
210
211 `GC.class_histogram` \[*options*\]
212 : Provides statistics about the Java heap usage.
213
214 Impact: High --- depends on Java heap size and content.
215
216 **Note:**
217
218 The *options* must be specified using either *key* or *key*`=`*value*
219 syntax.
220
221 *options*:
222
223 - `-all`: (Optional) Inspects all objects, including unreachable objects
224 (BOOLEAN, false)
225 - `-parallel`: (Optional) Number of parallel threads to use for heap inspection.
226 0 (the default) means let the VM determine the number of threads to use.
227 1 means use one thread (disable parallelism). For any other value the VM will
228 try to use the specified number of threads, but might use fewer. (INT, 0)
229
230 `GC.finalizer_info`
231 : Provides information about the Java finalization queue.
232
233 Impact: Medium
234
235 `GC.heap_dump` \[*options*\] *filename*
236 : Generates a HPROF format dump of the Java heap.
237
238 Impact: High --- depends on the Java heap size and content. Request a full
239 GC unless the `-all` option is specified.
240
241 **Note:**
242
243 The following *options* must be specified using either *key* or
244 *key*`=`*value* syntax.
245
246 *options*:
247
248 - `-all`: (Optional) Dump all objects, including unreachable objects
249 (BOOLEAN, false)
250 - `-gz`: (Optional) If specified, the heap dump is written in gzipped format
251 using the given compression level. 1 (recommended) is the fastest, 9 the
252 strongest compression. (INT, 1)
253 - `-overwrite`: (Optional) If specified, the dump file will be overwritten if
254 it exists (BOOLEAN, false)
255 - `-parallel`: (Optional) Number of parallel threads to use for heap dump. The VM will try to use the specified number of threads, but might use fewer. (INT, 1)
256
257 *arguments*:
258
259 - *filename*: The name of the dump file. If %p is specified in the filename, it is expanded to the JVM's PID. (FILE, no default value)
260
261 `GC.heap_info`
262 : Provides generic Java heap information.
263
264 Impact: Medium
265
266 `GC.run`
267 : Calls `java.lang.System.gc()`.
268
269 Impact: Medium --- depends on the Java heap size and content.
270
271 `GC.run_finalization`
272 : Calls `java.lang.System.runFinalization()`.
273
274 Impact: Medium --- depends on the Java content.
275
276 `JFR.check` \[*options*\]
277 : Show information about a running flight recording
278
279 Impact: Low
280
281 **Note:**
282
283 The *options* must be specified using either *key* or *key*`=`*value*
284 syntax. If no parameters are entered, information for all active recordings is shown.
285
286 *options*:
287
288 - `name`: (Optional) Name of the flight recording. (STRING, no default value)
289
290 - `verbose`: (Optional) Flag for printing the event settings for the recording
291 (BOOLEAN, false)
292
293 `JFR.configure` \[*options*\]
294 : Set the parameters for a flight recording
295
296 Impact: Low
297
298 **Note:**
299
300 The *options* must be specified using either *key* or *key*`=`*value*
301 syntax. If no parameters are entered, the current settings are displayed.
302
303 *options*:
304
305 - `dumppath`: (Optional) Path to the location where a recording file is written
306 in case the VM runs into a critical error, such as a system
307 crash. (STRING, The default location is the current directory)
308
309 - `globalbuffercount`: (Optional) Number of global buffers. This option is
310 a legacy option: change the `memorysize` parameter to alter the number of
311 global buffers. This value cannot be changed once JFR has been initialized.
312 (STRING, default determined by the value for `memorysize`)
313
314 - `globalbuffersize`: (Optional) Size of the global buffers, in bytes. This
315 option is a legacy option: change the `memorysize` parameter to alter
316 the size of the global buffers. This value cannot be changed once JFR
317 has been initialized. (STRING, default determined by the value for `memorysize`)
318
319 - `maxchunksize`: (Optional) Maximum size of an individual data chunk in bytes
320 if one of the following suffixes is not used: 'm' or 'M' for megabytes OR
321 'g' or 'G' for gigabytes. This value cannot be changed once JFR has been
322 initialized. (STRING, 12M)
323
324 - `memorysize`: (Optional) Overall memory size, in bytes if one of the following
325 suffixes is not used: 'm' or 'M' for megabytes OR 'g' or 'G' for gigabytes.
326 This value cannot be changed once JFR has been initialized. (STRING, 10M)
327
328 - `repositorypath`: (Optional) Path to the location where recordings are stored
329 until they are written to a permanent file. (STRING, The default location is
330 the temporary directory for the operating system. On Linux operating systems,
331 the temporary directory is `/tmp`. On Windwows, the temporary directory is
332 specified by the `TMP` environment variable.)
333
334 - `preserve-repository=`{`true`\|`false`} : Specifies whether files stored in
335 the disk repository should be kept after the JVM has exited. If false, files
336 are deleted. By default, this parameter is disabled.
337
338 - `stackdepth`: (Optional) Stack depth for stack traces. Setting this value
339 greater than the default of 64 may cause a performance degradation.
340 This value cannot be changed once JFR has been initialized. (LONG, 64)
341
342 - `thread_buffer_size`: (Optional) Local buffer size for each thread in bytes if one
343 of the following suffixes is not used: 'k' or 'K' for kilobytes or 'm' or 'M'
344 for megabytes. Overriding this parameter could reduce performance and is
345 not recommended. This value cannot be changed once JFR has been initialized.
346 (STRING, 8k)
347
348 - `samplethreads`: (Optional) Flag for activating thread sampling. (BOOLEAN, true)
349
350 `JFR.dump` \[*options*\]
351 : Write data to a file while a flight recording is running
352
353 Impact: Low
354
355 **Note:**
356
357 The *options* must be specified using either *key* or *key*`=`*value* syntax.
358 No options are required. The recording continues to run after the data is written.
359
360 *options*:
361
362 - `begin`: (Optional) Specify the time from which recording data will be included
363 in the dump file. The format is specified as local time. (STRING, no default value)
364
365 - `end`: (Optional) Specify the time to which recording data will be included in the
366 dump file. The format is specified as local time. (STRING, no default value)
367
368 **Note:** For both `begin` and `end`, the time must be in a format that can be read
369 by java.time.LocalTime::parse(STRING), java.time.LocalDateTime::parse(STRING)
370 or java.time.Instant::parse(STRING). For example, "13:20:15", "2020-03-17T09:00:00"
371 or "2020-03-17T09:00:00Z".
372
373 **Note:** `begin` and `end` times correspond to the timestamps found within the recorded
374 information in the flight recording data.
375
376 Another option is to use a time relative to the current time that is specified
377 by a negative integer followed by "s", "m" or "h". For example, "-12h", "-15m" or "-30s"
378
379 - `filename`: (Optional) Name of the file to which the flight recording data
380 is dumped. If no filename is given, a filename is generated from the PID and
381 the current date. The filename may also be a directory in which case, the filename
382 is generated from the PID and the current date in the specified directory.
383 If %p and/or %t is specified in the filename, it expands to the JVM's PID and
384 the current timestamp, respectively.
385 (FILE, no default value)
386
387 - `maxage`: (Optional) Length of time for dumping the flight recording data
388 to a file. (INTEGER followed by 's' for seconds 'm' for minutes or 'h' for hours,
389 no default value)
390
391 - `maxsize`: (Optional) Maximum size for the amount of data to dump from a flight
392 recording in bytes if one of the following suffixes is not used: 'm' or 'M' for megabytes
393 OR 'g' or 'G' for gigabytes. (STRING, no default value)
394
395 - `name`: (Optional) Name of the recording. If no name is given, data
396 from all recordings is dumped. (STRING, no default value)
397
398 - `path-to-gc-roots`: (Optional) Flag for saving the path to garbage collection (GC)
399 roots at the time the recording data is dumped. The path information is useful for
400 finding memory leaks but collecting it can cause the application to pause for
401 a short period of time. Turn on this flag only when you have an application
402 that you suspect has a memory leak. (BOOLEAN, false)
403
404 `JFR.start` \[*options*\]
405 : Start a flight recording
406
407 Impact: Low
408
409 **Note:**
410
411 The *options* must be specified using either *key* or *key*`=`*value*
412 syntax. If no parameters are entered, then a recording is started with default values.
413
414 *options*:
415
416 - `delay`: (Optional) Length of time to wait before starting to record
417 (INTEGER followed by 's' for seconds 'm' for minutes or 'h' for hours, 0s)
418
419 - `disk`: (Optional) Flag for also writing the data to disk while recording
420 (BOOLEAN, true)
421
422 - `dumponexit`: (Optional) Flag for writing the recording to disk when the
423 Java Virtual Machine (JVM) shuts down. If set to 'true' and no value is given
424 for `filename`, the recording is written to a file in the directory where
425 the process was started. The file name is a system-generated name that
426 contains the process ID, the recording ID and the current time stamp.
427 (For example: `id-1-2019_12_12_10_41.jfr`) (BOOLEAN, false)
428
429 - `duration`: (Optional) Length of time to record. Note that `0s` means forever
430 (INTEGER followed by 's' for seconds 'm' for minutes or 'h' for hours, 0s)
431
432 - `filename`: (Optional) Name of the file to which the flight recording data
433 is written when the recording is stopped. If no filename is given, a filename
434 is generated from the PID and the current date and is placed in the directory
435 where the process was started. The filename may also be a directory in which case,
436 the filename is generated from the PID and the current date in the specified directory.
437 If %p and/or %t is specified in the filename, it expands to the JVM's PID
438 and the current timestamp, respectively.
439 (FILE, no default value)
440
441 - `maxage`: (Optional) Maximum time to keep the recorded data on disk. This
442 parameter is valid only when the `disk` parameter is set to `true`. Note
443 `0s` means forever. (INTEGER followed by 's' for seconds 'm'
444 for minutes or 'h' for hours, 0s)
445
446 - `maxsize`: (Optional) Maximum size of the data to keep on disk in bytes if one
447 of the following suffixes is not used: 'm' or 'M' for megabytes OR 'g' or 'G' for gigabytes.
448 This parameter is valid only when the `disk` parameter is set to 'true'. The value must
449 not be less than the value for the `maxchunksize` parameter set with the `JFR.configure` command.
450 (STRING, 0 (no maximum size))
451
452 - `name`: (Optional) Name of the recording. If no name is provided, a name is generated.
453 Make note of the generated name that is shown in the response to the command so that
454 you can use it with other commands. (STRING, system-generated default name)
455
456 - `path-to-gc-roots`: (Optional) Flag for saving the path to garbage collection (GC)
457 roots at the end of a recording. The path information is useful for finding memory leaks
458 but collecting it is time consuming. Turn on this flag only when you
459 have an application that you suspect has a memory leak. If the `settings` parameter
460 is set to 'profile', then the information collected includes the stack trace
461 from where the potential leaking object was allocated. (BOOLEAN, false)
462
463 - `settings`: (Optional) Name of the settings file that identifies which events to record.
464 To specify more than one file, separate the names with a comma (','). Include the path
465 if the file is not in `JAVA-HOME`/lib/jfr. The following profiles are included with
466 the JDK in the `JAVA-HOME`/lib/jfr directory: 'default.jfc': collects a predefined set
467 of information with low overhead, so it has minimal impact on performance and can be
468 used with recordings that run continuously; 'profile.jfc': Provides more data than the
469 'default.jfc' profile, but with more overhead and impact on performance. Use this
470 configuration for short periods of time when more information is needed. Use `none` to
471 start a recording without a predefined configuration file.
472 (STRING, `JAVA-HOME`/lib/jfr/default.jfc)
473
474 Event settings and .jfc options can be specified using the following syntax:
475
476 - `option`: (Optional) Specifies the option value to modify. To list available
477 options, use the `JAVA_HOME`/bin/jfr tool.
478
479 - `event-setting`: (Optional) Specifies the event setting value to modify. Use the form:
480 `<event-name>#<setting-name>=<value>`
481 To add a new event setting, prefix the event name with '+'.
482
483 You can specify values for multiple event settings and .jfc options by
484 separating them with a whitespace. In case of a conflict between a parameter
485 and a .jfc option, the parameter will take precedence. The whitespace
486 delimiter can be omitted for timespan values, i.e. 20ms. For more
487 information about the settings syntax, see Javadoc of the jdk.jfr
488 package.
489
490 `JFR.stop` \[*options*\]
491 : Stop a flight recording
492
493 Impact: Low
494
495 **Note:**
496
497 The *options* must be specified using either *key* or *key*`=`*value*
498 syntax. If no parameters are entered, then no recording is stopped.
499
500 *options*:
501
502 - `filename`: (Optional) Name of the file to which the recording is
503 written when the recording is stopped. If %p and/or %t is specified
504 in the filename, it expands to the JVM's PID and the current
505 timestamp, respectively. If no path is provided, the data from the
506 recording is discarded. (FILE, no default value)
507
508 - `name`: (Optional) Name of the recording (STRING, no default value)
509
510
511 `JFR.view` \[*options*\]
512 : Display event data in predefined views.
513
514 Impact: Medium
515
516 **Note:**
517
518 The *options* must be specified using either *key* or *key*`=`*value*
519 syntax. If no parameters are entered, then a list of available views
520 are displayed.
521
522 *options*:
523
524 - `cell-height`: (Optional) Maximum number of rows in a table cell.
525 (INT, default value depends on the view)
526
527 - `maxage`: (Optional) Length of time for the view to span.
528 (INT followed by 's' for seconds 'm' for minutes or 'h' for hours,
529 default value is 10m)
530
531 - `maxsize`: (Optional) Maximum size for the view to span in bytes if one
532 of the following suffixes is not used: 'm' or 'M' for megabytes OR
533 'g' or 'G' for gigabytes. (STRING, default value is 32MB)
534
535 - `truncate`: (Optional) Maximum number of rows in a table cell.
536 (INT, default value depends on the view)
537
538 - `verbose`: (Optional) Displays the query that makes up the view.
539 (BOOLEAN, default value is false)
540
541 - `width`: (Optional) The width of the view in characters. (INT,
542 default value depends on the view)
543
544 *arguments*:
545
546 - `view`: Name of the view or event type to display. Use `help JFR.view`
547 to see a list of available views. (STRING, no default value)
548
549 The view parameter can be an event type name. Use `JFR.view types` to see
550 a list. To display all views, use `JFR.view all-views`. To display all
551 events, use `JFR.view all-events`.
552
553 `JVMTI.agent_load` \[*arguments*\]
554 : Loads JVMTI native agent.
555
556 Impact: Low
557
558 *arguments*:
559
560 - *library path*: Absolute path of the JVMTI agent to load. (STRING, no
561 default value)
562
563 - *agent option*: (Optional) Option string to pass the agent. (STRING, no
564 default value)
565
566 `JVMTI.data_dump`
567 : Signal the JVM to do a data-dump request for JVMTI.
568
569 Impact: High
570
571 `ManagementAgent.start` \[*options*\]
572 : Starts remote management agent.
573
574 Impact: Low --- no impact
575
576 **Note:**
577
578 The following *options* must be specified using either *key* or
579 *key*`=`*value* syntax.
580
581 *options*:
582
583 - `config.file`: (Optional) Sets `com.sun.management.config.file`
584 (STRING, no default value)
585
586 - `jmxremote.host`: (Optional) Sets `com.sun.management.jmxremote.host`
587 (STRING, no default value)
588
589 - `jmxremote.port`: (Optional) Sets `com.sun.management.jmxremote.port`
590 (STRING, no default value)
591
592 - `jmxremote.rmi.port`: (Optional) Sets
593 `com.sun.management.jmxremote.rmi.port` (STRING, no default value)
594
595 - `jmxremote.ssl`: (Optional) Sets `com.sun.management.jmxremote.ssl`
596 (STRING, no default value)
597
598 - `jmxremote.registry.ssl`: (Optional) Sets
599 `com.sun.management.jmxremote.registry.ssl` (STRING, no default value)
600
601 - `jmxremote.authenticate`: (Optional) Sets
602 `com.sun.management.jmxremote.authenticate` (STRING, no default value)
603
604 - jmxremote.password.file: (Optional) Sets
605 `com.sun.management.jmxremote.password.file` (STRING, no default value)
606
607 - `jmxremote.access.file`: (Optional) Sets
608 `com.sun.management.jmxremote.acce ss.file` (STRING, no default value)
609
610 - `jmxremote.login.config`: (Optional) Sets
611 `com.sun.management.jmxremote.log in.config` (STRING, no default value)
612
613 - `jmxremote.ssl.enabled.cipher.suites`: (Optional) Sets
614 `com.sun.management`.
615
616 - `jmxremote.ssl.enabled.cipher.suite`: (STRING, no default value)
617
618 - `jmxremote.ssl.enabled.protocols`: (Optional) Sets
619 `com.sun.management.jmxr emote.ssl.enabled.protocols` (STRING, no
620 default value)
621
622 - `jmxremote.ssl.need.client.auth`: (Optional) Sets
623 `com.sun.management.jmxre mote.need.client.auth` (STRING, no default
624 value)
625
626 - `jmxremote.ssl.config.file`: (Optional) Sets
627 `com.sun.management.jmxremote. ssl_config_file` (STRING, no default
628 value)
629
630 - `jmxremote.autodiscovery`: (Optional) Sets
631 `com.sun.management.jmxremote.au todiscovery` (STRING, no default
632 value)
633
634 - `jdp.port`: (Optional) Sets `com.sun.management.jdp.port` (INT, no
635 default value)
636
637 - `jdp.address`: (Optional) Sets `com.sun.management.jdp.address`
638 (STRING, no default value)
639
640 - `jdp.source_addr`: (Optional) Sets `com.sun.management.jdp.source_addr`
641 (STRING, no default value)
642
643 - `jdp.ttl`: (Optional) Sets `com.sun.management.jdp.ttl` (INT, no
644 default value)
645
646 - `jdp.pause`: (Optional) Sets `com.sun.management.jdp.pause` (INT, no
647 default value)
648
649 - `jdp.name`: (Optional) Sets `com.sun.management.jdp.name` (STRING, no
650 default value)
651
652 `ManagementAgent.start_local`
653 : Starts the local management agent.
654
655 Impact: Low --- no impact
656
657 `ManagementAgent.status`
658 : Print the management agent status.
659
660 Impact: Low --- no impact
661
662 `ManagementAgent.stop`
663 : Stops the remote management agent.
664
665 Impact: Low --- no impact
666
667 `System.dump_map` \[*options*\] (Linux only)
668 : Dumps an annotated process memory map to an output file.
669
670 Impact: Low
671
672 **Note:**
673
674 The following *options* must be specified using either *key* or
675 *key*`=`*value* syntax.
676
677 *options*:
678
679 - `-H`: (Optional) Human readable format (BOOLEAN, false)
680 - `-F`: (Optional) File path. If %p is specified in the filename, it is expanded to the JVM's PID. (FILE, "vm_memory_map_%p.txt")
681
682 `System.map` \[*options*\] (Linux only)
683 : Prints an annotated process memory map of the VM process.
684
685 Impact: Low
686
687 **Note:**
688
689 The following *options* must be specified using either *key* or
690 *key*`=`*value* syntax.
691
692 *options*:
693
694 - `-H`: (Optional) Human readable format (BOOLEAN, false)
695
696 `System.native_heap_info` (Linux only)
697 : Attempts to output information regarding native heap usage through malloc_info(3). If unsuccessful outputs "Error: " and a reason.
698
699 Impact: Low
700
701 `System.trim_native_heap` (Linux only)
702 : Attempts to free up memory by trimming the C-heap.
703
704 Impact: Low
705
706 `Thread.dump_to_file` \[*options*\] *filepath*
707 : Dump threads, with stack traces, to a file in plain text or JSON format.
708
709 Impact: Medium: Depends on the number of threads.
710
711 **Note:**
712
713 The following *options* must be specified using either *key* or
714 *key*`=`*value* syntax.
715
716 *options*:
717
718 - `-overwrite`: (Optional) May overwrite existing file (BOOLEAN, false)
719 - `-format`: (Optional) Output format ("plain" or "json") (STRING, plain)
720
721 *arguments*:
722
723 - *filepath*: The file path to the output file. If %p is specified in the filename, it is expanded to the JVM's PID. (FILE, no default value)
724
725 `Thread.print` \[*options*\]
726 : Prints all threads with stacktraces.
727
728 Impact: Medium --- depends on the number of threads.
729
730 **Note:**
731
732 The following *options* must be specified using either *key* or
733 *key*`=`*value* syntax.
734
735 *options*:
736
737 - `-e`: (Optional) Print extended thread information (BOOLEAN, false)
738 - `-l`: (Optional) Prints `java.util.concurrent` locks (BOOLEAN, false)
739
740 `VM.cds` \[*arguments*\]
741 : Dump a static or dynamic shared archive that includes all currently loaded classes.
742
743 Impact: Medium --- pause time depends on number of loaded classes
744
745 *arguments*:
746
747 - *subcmd*: must be either `static_dump` or `dynamic_dump` (STRING, no default value)
748 - *filename*: (Optional) Name of the shared archive to be dumped. If %p is specified in the filename, it is expanded to the JVM's PID. (FILE, "java_pid%p_\<subcmd\>.jsa")
749
750 If `dynamic_dump` is specified, the target JVM must be started with the JVM option
751 `-XX:+RecordDynamicDumpInfo`.
752
753 `VM.class_hierarchy` \[*options*\] \[*arguments*\]
754 : Print a list of all loaded classes, indented to show the class hierarchy.
755 The name of each class is followed by the ClassLoaderData\* of its
756 ClassLoader, or "null" if it is loaded by the bootstrap class loader.
757
758 Impact: Medium --- depends on the number of loaded classes.
759
760 **Note:**
761
762 The following *options* must be specified using either *key* or
763 *key*`=`*value* syntax.
764
765 *options*:
766
767 - `-i`: (Optional) Inherited interfaces should be printed. (BOOLEAN,
768 false)
769
770 - `-s`: (Optional) If a classname is specified, print its subclasses
771 in addition to its superclasses. Without this option only the
772 superclasses will be printed. (BOOLEAN, false)
773
774 *arguments*:
775
776 - *classname*: (Optional) The name of the class whose hierarchy should be
777 printed. If not specified, all class hierarchies are printed. (STRING,
778 no default value)
779
780 `VM.classes` \[*options*\]
781 : Print all loaded classes
782
783 Impact: Medium: Depends on number of loaded classes.
784
785 The following *options* must be specified using either *key* or
786 *key*`=`*value* syntax.
787
788 *options*:
789
790 - `-verbose`: (Optional) Dump the detailed content of a Java class.
791 Some classes are annotated with flags: `F` = has, or inherits, a non-empty finalize method,
792 `f` = has final method, `W` = methods rewritten, `C` = marked with `@Contended` annotation,
793 `R` = has been redefined, `S` = is shared class (BOOLEAN, false)
794
795 `VM.classloader_stats`
796 : Print statistics about all ClassLoaders.
797
798 Impact: Low
799
800 `VM.classloaders` \[*options*\]
801 : Prints classloader hierarchy.
802
803 Impact: Medium --- Depends on number of class loaders and classes loaded.
804
805 The following *options* must be specified using either *key* or
806 *key*`=`*value* syntax.
807
808 *options*:
809
810 - `show-classes`: (Optional) Print loaded classes. (BOOLEAN, false)
811 - `verbose`: (Optional) Print detailed information. (BOOLEAN, false)
812 - `fold`: (Optional) Show loaders of the same name and class as one. (BOOLEAN, true)
813
814 `VM.command_line`
815 : Print the command line used to start this VM instance.
816
817 Impact: Low
818
819 `VM.dynlibs`
820 : Print loaded dynamic libraries.
821
822 Impact: Low
823
824 `VM.events` \[*options*\]
825 : Print VM event logs
826
827 Impact: Low --- Depends on event log size.
828
829 *options*:
830
831 **Note:**
832
833 The following *options* must be specified using either *key* or
834 *key*`=`*value* syntax.
835
836 - `log`: (Optional) Name of log to be printed.
837 If omitted, all logs are printed. (STRING, no default value)
838 - `max`: (Optional) Maximum number of events to be printed (newest first).
839 If omitted, all events are printed. (STRING, no default value)
840
841 `VM.flags` \[*options*\]
842 : Print the VM flag options and their current values.
843
844 Impact: Low
845
846 **Note:**
847
848 The following *options* must be specified using either *key* or
849 *key*`=`*value* syntax.
850
851 *options*:
852
853 - `-all`: (Optional) Prints all flags supported by the VM (BOOLEAN,
854 false).
855
856 `VM.info`
857 : Print information about the JVM environment and status.
858
859 Impact: Low
860
861 `VM.log` \[*options*\]
862 : Lists current log configuration, enables/disables/configures a log output,
863 or rotates all logs.
864
865 Impact: Low
866
867 *options*:
868
869 **Note:**
870
871 The following *options* must be specified using either *key* or
872 *key*`=`*value* syntax.
873
874 - `output`: (Optional) The name or index (\#) of output to configure.
875 (STRING, no default value)
876
877 - `output_options`: (Optional) Options for the output. (STRING, no
878 default value)
879
880 - `what`: (Optional) Configures what tags to log. (STRING, no default
881 value )
882
883 - `decorators`: (Optional) Configures which decorators to use. Use 'none'
884 or an empty value to remove all. (STRING, no default value)
885
886 - `disable`: (Optional) Turns off all logging and clears the log
887 configuration. (BOOLEAN, no default value)
888
889 - `list`: (Optional) Lists current log configuration. (BOOLEAN, no
890 default value)
891
892 - `rotate`: (Optional) Rotates all logs. (BOOLEAN, no default value)
893
894 `VM.metaspace` \[*options*\]
895 : Prints the statistics for the metaspace
896
897 Impact: Medium --- Depends on number of classes loaded.
898
899 **Note:**
900
901 The following *options* must be specified using either *key* or
902 *key*`=`*value* syntax.
903
904 *options*:
905
906 - `basic`: (Optional) Prints a basic summary (does not need a safepoint). (BOOLEAN, false)
907 - `show-loaders`: (Optional) Shows usage by class loader. (BOOLEAN, false)
908 - `show-classes`: (Optional) If show-loaders is set, shows loaded classes for each loader. (BOOLEAN, false)
909 - `by-chunktype`: (Optional) Break down numbers by chunk type. (BOOLEAN, false)
910 - `by-spacetype`: (Optional) Break down numbers by loader type. (BOOLEAN, false)
911 - `vslist`: (Optional) Shows details about the underlying virtual space. (BOOLEAN, false)
912 - `chunkfreelist`: (Optional) Shows details about global chunk free lists (ChunkManager). (BOOLEAN, false)
913 - `scale`: (Optional) Memory usage in which to scale. Valid values are: 1, KB, MB
914 or GB (fixed scale) or "dynamic" for a dynamically chosen scale. (STRING, dynamic)
915
916 `VM.native_memory` \[*options*\]
917 : Print native memory usage
918
919 Impact: Medium
920
921 **Note:**
922
923 The following *options* must be specified using either *key* or
924 *key*`=`*value* syntax.
925
926 *options*:
927
928 - `summary`: (Optional) Requests runtime to report current memory
929 summary, which includes total reserved and committed memory, along with
930 memory usage summary by each subsystem. (BOOLEAN, false)
931
932 - `detail`: (Optional) Requests runtime to report memory allocation >=
933 1K by each callsite. (BOOLEAN, false)
934
935 - `baseline`: (Optional) Requests runtime to baseline current memory
936 usage, so it can be compared against in later time. (BOOLEAN, false)
937
938 - `summary.diff`: (Optional) Requests runtime to report memory summary
939 comparison against previous baseline. (BOOLEAN, false)
940
941 - `detail.diff`: (Optional) Requests runtime to report memory detail
942 comparison against previous baseline, which shows the memory allocation
943 activities at different callsites. (BOOLEAN, false)
944
945 - `statistics`: (Optional) Prints tracker statistics for tuning purpose.
946 (BOOLEAN, false)
947
948 - `scale`: (Optional) Memory usage in which scale, KB, MB or GB (STRING,
949 KB)
950
951 `VM.set_flag` \[*arguments*\]
952 : Sets VM flag option using the provided value.
953
954 Impact: Low
955
956 *arguments*:
957
958 - *flag name*: The name of the flag that you want to set (STRING, no
959 default value)
960
961 - *string value*: (Optional) The value that you want to set (STRING, no
962 default value)
963
964 `VM.stringtable` \[*options*\]
965 : Dump string table.
966
967 Impact: Medium --- depends on the Java content.
968
969 **Note:**
970
971 The following *options* must be specified using either *key* or
972 *key*`=`*value* syntax.
973
974 *options*:
975
976 - `-verbose`: (Optional) Dumps the content of each string in the table
977 (BOOLEAN, false)
978
979 `VM.symboltable` \[*options*\]
980 : Dump symbol table.
981
982 Impact: Medium --- depends on the Java content.
983
984 **Note:**
985
986 The following *options* must be specified using either *key* or
987 *key*`=`*value* syntax).
988
989 *options*:
990
991 - `-verbose`: (Optional) Dumps the content of each symbol in the table
992 (BOOLEAN, false)
993
994 `VM.system_properties`
995 : Print system properties.
996
997 Impact: Low
998
999 `VM.systemdictionary`
1000 : Prints the statistics for dictionary hashtable sizes and bucket length.
1001
1002 Impact: Medium
1003
1004 **Note:**
1005
1006 The following *options* must be specified using either *key* or
1007 *key*`=`*value* syntax.
1008
1009 *options*:
1010
1011 - `verbose`: (Optional) Dump the content of each dictionary entry for all
1012 class loaders (BOOLEAN, false) .
1013
1014 `VM.uptime` \[*options*\]
1015 : Print VM uptime.
1016
1017 Impact: Low
1018
1019 **Note:**
1020
1021 The following *options* must be specified using either *key* or
1022 *key*`=`*value* syntax.
1023
1024 *options*:
1025
1026 - `-date`: (Optional) Adds a prefix with the current date (BOOLEAN,
1027 false)
1028
1029 `VM.version`
1030 : Print JVM version information.
1031
1032 Impact: Low