1JCMD(1) JDK Commands JCMD(1)
2
6 jcmd - send diagnostic command requests to a running Java Virtual Ma‐
7 chine (JVM)
8
10 jcmd [pid | main-class] command... | PerfCounter.print | -f filename
11 jcmd [-l]
13 jcmd -h
15 pid When used, the jcmd utility sends the diagnostic command request
17 to the process ID for the Java process.
18 main-class
20 When used, the jcmd utility sends the diagnostic command request
21 to all Java processes with the specified name of the main class.
22 command
24 The command must be a valid jcmd command for the selected JVM.
25 The list of available commands for jcmd is obtained by running
26 the help command (jcmd pid help) where pid is the process ID for
27 the running Java process. If the pid is 0, commands will be
28 sent to all Java processes. The main class argument will be
29 used to match, either partially or fully, the class used to
30 start Java. If no options are given, it lists the running Java
31 process identifiers with the main class and command-line argu‐
32 ments that were used to launch the process (the same as using
33 -l).
34 Perfcounter.print
36 Prints the performance counters exposed by the specified Java
37 process.
38 -f filename
40 Reads and executes commands from a specified file, filename.
41 -l Displays the list of Java Virtual Machine process identifiers
43 that are not running in a separate docker process along with the
44 main class and command-line arguments that were used to launch
45 the process. If the JVM is in a docker process, you must use
46 tools such as ps to look up the PID.
47 Note:
49 Using jcmd without arguments is the same as using jcmd -l.
51 -h Displays the jcmd utility's command-line help.
53
55 The jcmd utility is used to send diagnostic command requests to the
56 JVM. It must be used on the same machine on which the JVM is running,
57 and have the same effective user and group identifiers that were used
58 to launch the JVM. Each diagnostic command has its own set of argu‐
59 ments. To display the description, syntax, and a list of available ar‐
60 guments for a diagnostic command, use the name of the command as the
61 argument. For example:
62 jcmd pid help command
64 If arguments contain spaces, then you must surround them with single or
66 double quotation marks (' or "). In addition, you must escape single
67 or double quotation marks with a backslash (\) to prevent the operating
68 system shell from processing quotation marks. Alternatively, you can
69 surround these arguments with single quotation marks and then with dou‐
70 ble quotation marks (or with double quotation marks and then with sin‐
71 gle quotation marks).
72 If you specify the process identifier (pid) or the main class (main-
74 class) as the first argument, then the jcmd utility sends the diagnos‐
75 tic command request to the Java process with the specified identifier
76 or to all Java processes with the specified name of the main class.
77 You can also send the diagnostic command request to all available Java
78 processes by specifying 0 as the process identifier.
79
81 The command must be a valid jcmd diagnostic command for the selected
82 JVM. The list of available commands for jcmd is obtained by running
83 the help command (jcmd pid help) where pid is the process ID for a run‐
84 ning Java process. If the pid is 0, commands will be sent to all Java
85 processes. The main class argument will be used to match, either par‐
86 tially or fully, the class used to start Java. If no options are giv‐
87 en, it lists the running Java process identifiers that are not in sepa‐
88 rate docker processes along with the main class and command-line argu‐
89 ments that were used to launch the process (the same as using -l).
90 The following commands are available:
92 help [options] [arguments]
94 For more information about a specific command.
95 arguments:
97 • command name: The name of the command for which we want help
99 (STRING, no default value)
100 Note:
102 The following options must be specified using either key or
104 key=value syntax.
105 options:
107 • -all: (Optional) Show help for all commands (BOOLEAN, false) .
109 Compiler.codecache
111 Prints code cache layout and bounds.
112 Impact: Low
114 Compiler.codelist
116 Prints all compiled methods in code cache that are alive.
117 Impact: Medium
119 Compiler.perfmap (Linux only)
121 Write map file for Linux perf tool.
122 Impact: Low
124 Compiler.queue
126 Prints methods queued for compilation.
127 Impact: Low
129 Compiler.directives_add *filename* *arguments*
131 Adds compiler directives from a file.
132 Impact: Low
134 arguments:
136 filename: The name of the directives file (STRING, no default
138 value)
139 Compiler.directives_clear
141 Remove all compiler directives.
142 Impact: Low
144 Compiler.directives_print
146 Prints all active compiler directives.
147 Impact: Low
149 Compiler.directives_remove
151 Remove latest added compiler directive.
152 Impact: Low
154 GC.class_histogram [options]
156 Provides statistics about the Java heap usage.
157 Impact: High --- depends on Java heap size and content.
159 Note:
161 The options must be specified using either key or key=value syn‐
163 tax.
164 options:
166 • -all: (Optional) Inspects all objects, including unreachable
168 objects (BOOLEAN, false)
169 • -parallel: (Optional) Number of parallel threads to use for
171 heap inspection. 0 (the default) means let the VM determine
172 the number of threads to use. 1 means use one thread (disable
173 parallelism). For any other value the VM will try to use the
174 specified number of threads, but might use fewer. (INT, 0)
175 GC.finalizer_info
177 Provides information about the Java finalization queue.
178 Impact: Medium
180 GC.heap_dump [options] [arguments]
182 Generates a HPROF format dump of the Java heap.
183 Impact: High --- depends on the Java heap size and content. Re‐
185 quest a full GC unless the -all option is specified.
186 Note:
188 The following options must be specified using either key or
190 key=value syntax.
191 options:
193 • -all: (Optional) Dump all objects, including unreachable ob‐
195 jects (BOOLEAN, false)
196 • -gz: (Optional) If specified, the heap dump is written in
198 gzipped format using the given compression level. 1 (recom‐
199 mended) is the fastest, 9 the strongest compression. (INT, 1)
200 • -overwrite: (Optional) If specified, the dump file will be
202 overwritten if it exists (BOOLEAN, false)
203 arguments:
205 • filename: The name of the dump file (STRING, no default value)
207 GC.heap_info
209 Provides generic Java heap information.
210 Impact: Medium
212 GC.run Calls java.lang.System.gc().
214 Impact: Medium --- depends on the Java heap size and content.
216 GC.run_finalization
218 Calls java.lang.System.runFinalization().
219 Impact: Medium --- depends on the Java content.
221 JFR.check [options]
223 Show information about a running flight recording
224 Impact: Low
226 Note:
228 The options must be specified using either key or key=value syn‐
230 tax. If no parameters are entered, information for all active
231 recordings is shown.
232 options:
234 • name: (Optional) Name of the flight recording. (STRING, no
236 default value)
237 • verbose: (Optional) Flag for printing the event settings for
239 the recording (BOOLEAN, false)
240 JFR.configure [options]
242 Set the parameters for a flight recording
243 Impact: Low
245 Note:
247 The options must be specified using either key or key=value syn‐
249 tax. If no parameters are entered, the current settings are
250 displayed.
251 options:
253 • globalbuffercount: (Optional) Number of global buffers. This
255 option is a legacy option: change the memorysize parameter to
256 alter the number of global buffers. This value cannot be
257 changed once JFR has been initialized. (STRING, default de‐
258 termined by the value for memorysize)
259 • globalbuffersize: (Optional) Size of the global buffers, in
261 bytes. This option is a legacy option: change the memorysize
262 parameter to alter the size of the global buffers. This value
263 cannot be changed once JFR has been initialized. (STRING, de‐
264 fault determined by the value for memorysize)
265 • maxchunksize: (Optional) Maximum size of an individual data
267 chunk in bytes if one of the following suffixes is not used:
268 'm' or 'M' for megabytes OR 'g' or 'G' for gigabytes. This
269 value cannot be changed once JFR has been initialized.
270 (STRING, 12M)
271 • memorysize: (Optional) Overall memory size, in bytes if one of
273 the following suffixes is not used: 'm' or 'M' for megabytes
274 OR 'g' or 'G' for gigabytes. This value cannot be changed
275 once JFR has been initialized. (STRING, 10M)
276 • repositorypath: (Optional) Path to the location where record‐
278 ings are stored until they are written to a permanent file.
279 (STRING, The default location is the temporary directory for
280 the operating system. On Linux operating systems, the tempo‐
281 rary directory is /tmp. On Windwows, the temporary directory
282 is specified by the TMP environment variable.)
283 • preserve-repository={true|false} : Specifies whether files
285 stored in the disk repository should be kept after the JVM has
286 exited. If false, files are deleted. By default, this param‐
287 eter is disabled.
288 • stackdepth: (Optional) Stack depth for stack traces. Setting
290 this value greater than the default of 64 may cause a perfor‐
291 mance degradation. This value cannot be changed once JFR has
292 been initialized. (LONG, 64)
293 • thread_buffer_size: (Optional) Local buffer size for each
295 thread in bytes if one of the following suffixes is not used:
296 'k' or 'K' for kilobytes or 'm' or 'M' for megabytes. Over‐
297 riding this parameter could reduce performance and is not rec‐
298 ommended. This value cannot be changed once JFR has been ini‐
299 tialized. (STRING, 8k)
300 • samplethreads: (Optional) Flag for activating thread sampling.
302 (BOOLEAN, true)
303 JFR.dump [options]
305 Write data to a file while a flight recording is running
306 Impact: Low
308 Note:
310 The options must be specified using either key or key=value syn‐
312 tax. No options are required. The recording continues to run
313 after the data is written.
314 options:
316 • begin: (Optional) Specify the time from which recording data
318 will be included in the dump file. The format is specified as
319 local time. (STRING, no default value)
320 • end: (Optional) Specify the time to which recording data will
322 be included in the dump file. The format is specified as lo‐
323 cal time. (STRING, no default value)
324 Note: For both begin and end, the time must be in a format
326 that can be read by java.time.LocalTime::parse(STRING), ja‐
327 va.time.LocalDateTime::parse(STRING) or java.time.In‐
328 stant::parse(STRING). For example, "13:20:15",
329 "2020-03-17T09:00:00" or "2020-03-17T09:00:00Z".
330 Note: begin and end times correspond to the timestamps found
332 within the recorded information in the flight recording data.
333 Another option is to use a time relative to the current time
335 that is specified by a negative integer followed by "s", "m"
336 or "h". For example, "-12h", "-15m" or "-30s"
337 • filename: (Optional) Name of the file to which the flight
339 recording data is dumped. If no filename is given, a filename
340 is generated from the PID and the current date. The filename
341 may also be a directory in which case, the filename is gener‐
342 ated from the PID and the current date in the specified direc‐
343 tory. If %p and/or %t is specified in the filename, it ex‐
344 pands to the JVM's PID and the current timestamp, respective‐
345 ly. (STRING, no default value)
346 • maxage: (Optional) Length of time for dumping the flight
348 recording data to a file. (INTEGER followed by 's' for sec‐
349 onds 'm' for minutes or 'h' for hours, no default value)
350 • maxsize: (Optional) Maximum size for the amount of data to
352 dump from a flight recording in bytes if one of the following
353 suffixes is not used: 'm' or 'M' for megabytes OR 'g' or 'G'
354 for gigabytes. (STRING, no default value)
355 • name: (Optional) Name of the recording. If no name is given,
357 data from all recordings is dumped. (STRING, no default val‐
358 ue)
359 • path-to-gc-root: (Optional) Flag for saving the path to
361 garbage collection (GC) roots at the time the recording data
362 is dumped. The path information is useful for finding memory
363 leaks but collecting it can cause the application to pause for
364 a short period of time. Turn on this flag only when you have
365 an application that you suspect has a memory leak. (BOOLEAN,
366 false)
367 JFR.start [options]
369 Start a flight recording
370 Impact: Low
372 Note:
374 The options must be specified using either key or key=value syn‐
376 tax. If no parameters are entered, then a recording is started
377 with default values.
378 options:
380 • delay: (Optional) Length of time to wait before starting to
382 record (INTEGER followed by 's' for seconds 'm' for minutes or
383 'h' for hours, 0s)
384 • disk: (Optional) Flag for also writing the data to disk while
386 recording (BOOLEAN, true)
387 • dumponexit: (Optional) Flag for writing the recording to disk
389 when the Java Virtual Machine (JVM) shuts down. If set to
390 'true' and no value is given for filename, the recording is
391 written to a file in the directory where the process was
392 started. The file name is a system-generated name that con‐
393 tains the process ID, the recording ID and the current time
394 stamp. (For example: id-1-2019_12_12_10_41.jfr) (BOOLEAN,
395 false)
396 • duration: (Optional) Length of time to record. Note that 0s
398 means forever (INTEGER followed by 's' for seconds 'm' for
399 minutes or 'h' for hours, 0s)
400 • filename: (Optional) Name of the file to which the flight
402 recording data is written when the recording is stopped. If
403 no filename is given, a filename is generated from the PID and
404 the current date and is placed in the directory where the
405 process was started. The filename may also be a directory in
406 which case, the filename is generated from the PID and the
407 current date in the specified directory. If %p and/or %t is
408 specified in the filename, it expands to the JVM's PID and the
409 current timestamp, respectively. (STRING, no default value)
410 • maxage: (Optional) Maximum time to keep the recorded data on
412 disk. This parameter is valid only when the disk parameter is
413 set to true. Note 0s means forever. (INTEGER followed by 's'
414 for seconds 'm' for minutes or 'h' for hours, 0s)
415 • maxsize: (Optional) Maximum size of the data to keep on disk
417 in bytes if one of the following suffixes is not used: 'm' or
418 'M' for megabytes OR 'g' or 'G' for gigabytes. This parameter
419 is valid only when the disk parameter is set to 'true'. The
420 value must not be less than the value for the maxchunksize pa‐
421 rameter set with the JFR.configure command. (STRING, 0 (no
422 maximum size))
423 • name: (Optional) Name of the recording. If no name is provid‐
425 ed, a name is generated. Make note of the generated name that
426 is shown in the response to the command so that you can use it
427 with other commands. (STRING, system-generated default name)
428 • path-to-gc-root: (Optional) Flag for saving the path to
430 garbage collection (GC) roots at the end of a recording. The
431 path information is useful for finding memory leaks but col‐
432 lecting it is time consuming. Turn on this flag only when you
433 have an application that you suspect has a memory leak. If
434 the settings parameter is set to 'profile', then the informa‐
435 tion collected includes the stack trace from where the poten‐
436 tial leaking object was allocated. (BOOLEAN, false)
437 • settings: (Optional) Name of the settings file that identifies
439 which events to record. To specify more than one file, sepa‐
440 rate the names with a comma (','). Include the path if the
441 file is not in JAVA-HOME/lib/jfr. The following profiles are
442 included with the JDK in the JAVA-HOME/lib/jfr directory: 'de‐
443 fault.jfc': collects a predefined set of information with low
444 overhead, so it has minimal impact on performance and can be
445 used with recordings that run continuously; 'profile.jfc':
446 Provides more data than the 'default.jfc' profile, but with
447 more overhead and impact on performance. Use this configura‐
448 tion for short periods of time when more information is need‐
449 ed. Use none to start a recording without a predefined con‐
450 figuration file. (STRING, JAVA-HOME/lib/jfr/default.jfc)
451 Event settings and .jfc options can be specified using the fol‐
453 lowing syntax:
454 • option: (Optional) Specifies the option value to modify. To
456 list available options, use the JAVA_HOME/bin/jfr tool.
457 • event-setting: (Optional) Specifies the event setting value to
459 modify. Use the form: <event-name>#<setting-name>=<value> To
460 add a new event setting, prefix the event name with '+'.
461 You can specify values for multiple event settings and .jfc op‐
463 tions by separating them with a whitespace. In case of a con‐
464 flict between a parameter and a .jfc option, the parameter will
465 take precedence. The whitespace delimiter can be omitted for
466 timespan values, i.e. 20ms. For more information about the
467 settings syntax, see Javadoc of the jdk.jfr package.
468 JFR.stop [options]
470 Stop a flight recording
471 Impact: Low
473 Note:
475 The options must be specified using either key or key=value syn‐
477 tax. If no parameters are entered, then no recording is
478 stopped.
479 options:
481 • filename: (Optional) Name of the file to which the recording
483 is written when the recording is stopped. If %p and/or %t is
484 specified in the filename, it expands to the JVM's PID and the
485 current timestamp, respectively. If no path is provided, the
486 data from the recording is discarded. (STRING, no default
487 value)
488 • name: (Optional) Name of the recording (STRING, no default
490 value)
491 JVMTI.agent_load [arguments]
493 Loads JVMTI native agent.
494 Impact: Low
496 arguments:
498 • library path: Absolute path of the JVMTI agent to load.
500 (STRING, no default value)
501 • agent option: (Optional) Option string to pass the agent.
503 (STRING, no default value)
504 JVMTI.data_dump
506 Signals the JVM to do a data-dump request for JVMTI.
507 Impact: High
509 ManagementAgent.start [options]
511 Starts remote management agent.
512 Impact: Low --- no impact
514 Note:
516 The following options must be specified using either key or
518 key=value syntax.
519 options:
521 • config.file: (Optional) Sets com.sun.management.config.file
523 (STRING, no default value)
524 • jmxremote.host: (Optional) Sets com.sun.management.jmxre‐
526 mote.host (STRING, no default value)
527 • jmxremote.port: (Optional) Sets com.sun.management.jmxre‐
529 mote.port (STRING, no default value)
530 • jmxremote.rmi.port: (Optional) Sets com.sun.management.jmxre‐
532 mote.rmi.port (STRING, no default value)
533 • jmxremote.ssl: (Optional) Sets com.sun.management.jmxre‐
535 mote.ssl (STRING, no default value)
536 • jmxremote.registry.ssl: (Optional) Sets com.sun.manage‐
538 ment.jmxremote.registry.ssl (STRING, no default value)
539 • jmxremote.authenticate: (Optional) Sets com.sun.manage‐
541 ment.jmxremote.authenticate (STRING, no default value)
542 • jmxremote.password.file: (Optional) Sets com.sun.manage‐
544 ment.jmxremote.password.file (STRING, no default value)
545 • jmxremote.access.file: (Optional) Sets com.sun.manage‐
547 ment.jmxremote.acce ss.file (STRING, no default value)
548 • jmxremote.login.config: (Optional) Sets com.sun.manage‐
550 ment.jmxremote.log in.config (STRING, no default value)
551 • jmxremote.ssl.enabled.cipher.suites: (Optional) Sets
553 com.sun.management.
554 • jmxremote.ssl.enabled.cipher.suite: (STRING, no default value)
556 • jmxremote.ssl.enabled.protocols: (Optional) Sets com.sun.man‐
558 agement.jmxr emote.ssl.enabled.protocols (STRING, no default
559 value)
560 • jmxremote.ssl.need.client.auth: (Optional) Sets com.sun.man‐
562 agement.jmxre mote.need.client.auth (STRING, no default value)
563 • jmxremote.ssl.config.file: (Optional) Sets com.sun.manage‐
565 ment.jmxremote. ssl_config_file (STRING, no default value)
566 • jmxremote.autodiscovery: (Optional) Sets com.sun.manage‐
568 ment.jmxremote.au todiscovery (STRING, no default value)
569 • jdp.port: (Optional) Sets com.sun.management.jdp.port (INT, no
571 default value)
572 • jdp.address: (Optional) Sets com.sun.management.jdp.address
574 (STRING, no default value)
575 • jdp.source_addr: (Optional) Sets com.sun.manage‐
577 ment.jdp.source_addr (STRING, no default value)
578 • jdp.ttl: (Optional) Sets com.sun.management.jdp.ttl (INT, no
580 default value)
581 • jdp.pause: (Optional) Sets com.sun.management.jdp.pause (INT,
583 no default value)
584 • jdp.name: (Optional) Sets com.sun.management.jdp.name (STRING,
586 no default value)
587 ManagementAgent.start_local
589 Starts the local management agent.
590 Impact: Low --- no impact
592 ManagementAgent.status
594 Print the management agent status.
595 Impact: Low --- no impact
597 ManagementAgent.stop
599 Stops the remote management agent.
600 Impact: Low --- no impact
602 System.native_heap_info (Linux only)
604 Prints information about native heap usage through malloc_in‐
605 fo(3).
606 Impact: Low
608 System.trim_native_heap (Linux only)
610 Attempts to free up memory by trimming the C-heap.
611 Impact: Low
613 Thread.print [options]
615 Prints all threads with stacktraces.
616 Impact: Medium --- depends on the number of threads.
618 Note:
620 The following options must be specified using either key or
622 key=value syntax.
623 options:
625 • -e: (Optional) Print extended thread information (BOOLEAN,
627 false)
628 • -l: (Optional) Prints java.util.concurrent locks (BOOLEAN,
630 false)
631 VM.cds [arguments]
633 Dumps a static or dynamic shared archive that includes all cur‐
634 rently loaded classes.
635 Impact: Medium --- pause time depends on number of loaded class‐
637 es
638 arguments:
640 • subcmd: must be either static_dump or dynamic_dump (STRING, no
642 default value)
643 • filename: (Optional) Name of the shared archive to be dumped
645 (STRING, no default value)
646 If filename is not specified, a default file name is chosen us‐
648 ing the pid of the target JVM process. For example, ja‐
649 va_pid1234_static.jsa, java_pid5678_dynamic.jsa, etc.
650 If filename is not specified as an absolute path, the archive
652 file is created in a directory relative to the current directory
653 of the target JVM process.
654 If dynamic_dump is specified, the target JVM must be started
656 with the JVM option -XX:+RecordDynamicDumpInfo.
657 VM.classloaders [options]
659 Prints classloader hierarchy.
660 Impact: Medium --- Depends on number of class loaders and class‐
662 es loaded.
663 The following options must be specified using either key or
665 key=value syntax.
666 options:
668 • show-classes: (Optional) Print loaded classes. (BOOLEAN,
670 false)
671 • verbose: (Optional) Print detailed information. (BOOLEAN,
673 false)
674 • fold: (Optional) Show loaders of the same name and class as
676 one. (BOOLEAN, true)
677 VM.classloader_stats
679 Prints statistics about all ClassLoaders.
680 Impact: Low
682 VM.class_hierarchy [options] [arguments]
684 Prints a list of all loaded classes, indented to show the class
685 hierarchy. The name of each class is followed by the ClassLoad‐
686 erData* of its ClassLoader, or "null" if it is loaded by the
687 bootstrap class loader.
688 Impact: Medium --- depends on the number of loaded classes.
690 Note:
692 The following options must be specified using either key or
694 key=value syntax.
695 options:
697 • -i: (Optional) Inherited interfaces should be printed. (BOOL‐
699 EAN, false)
700 • -s: (Optional) If a classname is specified, print its sub‐
702 classes in addition to its superclasses. Without this option
703 only the superclasses will be printed. (BOOLEAN, false)
704 arguments:
706 • classname: (Optional) The name of the class whose hierarchy
708 should be printed. If not specified, all class hierarchies
709 are printed. (STRING, no default value)
710 VM.command_line
712 Prints the command line used to start this VM instance.
713 Impact: Low
715 VM.dynlibs
717 Prints the loaded dynamic libraries.
718 Impact: Low
720 VM.events [options]
722 Print VM event logs
723 Impact: Low --- Depends on event log size.
725 options:
727 Note:
729 The following options must be specified using either key or
731 key=value syntax.
732 • log: (Optional) Name of log to be printed. If omitted, all
734 logs are printed. (STRING, no default value)
735 • max: (Optional) Maximum number of events to be printed (newest
737 first). If omitted, all events are printed. (STRING, no de‐
738 fault value)
739 VM.info
741 Prints information about the JVM environment and status.
742 Impact: Low
744 VM.log [options]
746 Lists current log configuration, enables/disables/configures a
747 log output, or rotates all logs.
748 Impact: Low
750 options:
752 Note:
754 The following options must be specified using either key or
756 key=value syntax.
757 • output: (Optional) The name or index (#) of output to config‐
759 ure. (STRING, no default value)
760 • output_options: (Optional) Options for the output. (STRING,
762 no default value)
763 • what: (Optional) Configures what tags to log. (STRING, no de‐
765 fault value )
766 • decorators: (Optional) Configures which decorators to use.
768 Use 'none' or an empty value to remove all. (STRING, no de‐
769 fault value)
770 • disable: (Optional) Turns off all logging and clears the log
772 configuration. (BOOLEAN, no default value)
773 • list: (Optional) Lists current log configuration. (BOOLEAN,
775 no default value)
776 • rotate: (Optional) Rotates all logs. (BOOLEAN, no default
778 value)
779 VM.flags [options]
781 Prints the VM flag options and their current values.
782 Impact: Low
784 Note:
786 The following options must be specified using either key or
788 key=value syntax.
789 options:
791 • -all: (Optional) Prints all flags supported by the VM (BOOL‐
793 EAN, false).
794 VM.metaspace [options]
796 Prints the statistics for the metaspace
797 Impact: Medium --- Depends on number of classes loaded.
799 Note:
801 The following options must be specified using either key or
803 key=value syntax.
804 options:
806 • basic: (Optional) Prints a basic summary (does not need a
808 safepoint). (BOOLEAN, false)
809 • show-loaders: (Optional) Shows usage by class loader. (BOOL‐
811 EAN, false)
812 • show-classes: (Optional) If show-loaders is set, shows loaded
814 classes for each loader. (BOOLEAN, false)
815 • by-chunktype: (Optional) Break down numbers by chunk type.
817 (BOOLEAN, false)
818 • by-spacetype: (Optional) Break down numbers by loader type.
820 (BOOLEAN, false)
821 • vslist: (Optional) Shows details about the underlying virtual
823 space. (BOOLEAN, false)
824 • scale: (Optional) Memory usage in which to scale. Valid val‐
826 ues are: 1, KB, MB or GB (fixed scale) or "dynamic" for a dy‐
827 namically chosen scale. (STRING, dynamic)
828 VM.native_memory [options]
830 Prints native memory usage
831 Impact: Medium
833 Note:
835 The following options must be specified using either key or
837 key=value syntax.
838 options:
840 • summary: (Optional) Requests runtime to report current memory
842 summary, which includes total reserved and committed memory,
843 along with memory usage summary by each subsystem. (BOOLEAN,
844 false)
845 • detail: (Optional) Requests runtime to report memory alloca‐
847 tion >= 1K by each callsite. (BOOLEAN, false)
848 • baseline: (Optional) Requests runtime to baseline current mem‐
850 ory usage, so it can be compared against in later time.
851 (BOOLEAN, false)
852 • summary.diff: (Optional) Requests runtime to report memory
854 summary comparison against previous baseline. (BOOLEAN,
855 false)
856 • detail.diff: (Optional) Requests runtime to report memory de‐
858 tail comparison against previous baseline, which shows the
859 memory allocation activities at different callsites. (BOOL‐
860 EAN, false)
861 • statistics: (Optional) Prints tracker statistics for tuning
863 purpose. (BOOLEAN, false)
864 • scale: (Optional) Memory usage in which scale, KB, MB or GB
866 (STRING, KB)
867 VM.print_touched_methods
869 Prints all methods that have ever been touched during the life‐
870 time of this JVM.
871 Impact: Medium --- depends on Java content.
873 VM.set_flag [arguments]
875 Sets the VM flag option by using the provided value.
876 Impact: Low
878 arguments:
880 • flag name: The name of the flag that you want to set (STRING,
882 no default value)
883 • string value: (Optional) The value that you want to set
885 (STRING, no default value)
886 VM.stringtable [options]
888 Dumps the string table.
889 Impact: Medium --- depends on the Java content.
891 Note:
893 The following options must be specified using either key or
895 key=value syntax.
896 options:
898 • -verbose: (Optional) Dumps the content of each string in the
900 table (BOOLEAN, false)
901 VM.symboltable [options]
903 Dumps the symbol table.
904 Impact: Medium --- depends on the Java content.
906 Note:
908 The following options must be specified using either key or
910 key=value syntax).
911 options:
913 • -verbose: (Optional) Dumps the content of each symbol in the
915 table (BOOLEAN, false)
916 VM.systemdictionary
918 Prints the statistics for dictionary hashtable sizes and bucket
919 length.
920 Impact: Medium
922 Note:
924 The following options must be specified using either key or
926 key=value syntax.
927 options:
929 • verbose: (Optional) Dump the content of each dictionary entry
931 for all class loaders (BOOLEAN, false) .
932 VM.system_properties
934 Prints the system properties.
935 Impact: Low
937 VM.uptime [options]
939 Prints the VM uptime.
940 Impact: Low
942 Note:
944 The following options must be specified using either key or
946 key=value syntax.
947 options:
949 • -date: (Optional) Adds a prefix with the current date (BOOL‐
951 EAN, false)
952 VM.version
954 Prints JVM version information.
955 Impact: Low
957JDK 21 2023 JCMD(1)