1 .TH "LTTNG" "1" "July 18th, 2013" "" ""
4 lttng \(em LTTng 2.x tracer control command line tool
9 lttng [OPTIONS] <COMMAND>
13 The LTTng project aims at providing highly efficient tracing tools for Linux.
14 It's tracers help tracking down performance issues and debugging problems
15 involving multiple concurrent processes and threads. Tracing across multiple
16 systems is also possible.
18 The \fBlttng\fP command line tool from the lttng-tools package is used to control
19 both kernel and user-space tracing. Every interactions with the tracer should
20 be done by this tool or by the liblttng-ctl provided with the lttng-tools
23 LTTng uses a session daemon (lttng-sessiond(8)), acting as a tracing registry,
24 which allows you to interact with multiple tracers (kernel and user-space)
25 inside the same container, a tracing session. Traces can be gathered from the
26 kernel and/or instrumented applications (lttng-ust(3)). Aggregating and reading
27 those traces is done using the babeltrace(1) text viewer.
29 We introduce the notion of \fBtracing domains\fP which is essentially a type of
30 tracer (kernel or user space for now). In the future, we could see a third
31 tracer being for instance an hypervisor. For some commands, you'll need to
32 specify on which domain the command applies (-u or -k). For instance, enabling
33 a kernel event, you must specify the kernel domain to the command so we know
34 for which tracer this event is for.
36 In order to trace the kernel, the session daemon needs to be running as root.
37 LTTng provides the use of a \fBtracing group\fP (default: tracing). Whomever is
38 in that group can interact with the root session daemon and thus trace the
39 kernel. Session daemons can co-exist meaning that you can have a session daemon
40 running as Alice that can be used to trace her applications along side with a
41 root daemon or even a Bob daemon. We highly recommend to start the session
42 daemon at boot time for stable and long term tracing.
44 Every user-space applications instrumented with lttng-ust(3), will
45 automatically register to the session daemon. This feature gives you the
46 ability to list available traceable applications and tracepoints on a per user
47 basis. (See \fBlist\fP command).
51 This program follow the usual GNU command line syntax with long options starting with
52 two dashes. Below is a summary of the available options.
57 Show summary of possible options and commands.
59 .BR "\-v, \-\-verbose"
61 Three levels of verbosity are available which are triggered by putting additional v to
62 the option (\-vv or \-vvv)
65 Suppress all messages (even errors).
67 .BR "\-g, \-\-group NAME"
68 Set unix tracing group name. (default: tracing)
70 .BR "\-n, \-\-no-sessiond"
71 Don't automatically spawn a session daemon.
73 .BR "\-\-sessiond\-path PATH"
74 Set session daemon full binary path.
76 .BR "\-\-list\-options"
77 Simple listing of lttng options.
79 .BR "\-\-list\-commands"
80 Simple listing of lttng commands.
84 \fBadd-context\fP [OPTIONS]
86 Add context to event(s) and/or channel(s).
88 A context is basically extra information appended to a channel. For instance,
89 you could ask the tracer to add the PID information for all events in a
90 channel. You can also add performance monitoring unit counters (perf PMU) using
93 For example, this command will add the context information 'prio' and two perf
94 counters (hardware branch misses and cache misses), to all events in the trace
98 # lttng add-context \-k \-t prio \-t perf:branch-misses \\
102 Please take a look at the help (\-h/\-\-help) for a detailed list of available
105 If no channel is given (\-c), the context is added to all channels that were
106 already enabled. If the session has no channel, a default channel is created.
107 If \fB\-c, \-\-channel\fP is omitted, but a non-default channel already
108 exists within the session, an error is returned. Otherwise the context
109 will be added only to the given channel (\-c).
111 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
118 Show summary of possible options and commands.
120 .BR "\-s, \-\-session NAME"
121 Apply on session name.
123 .BR "\-c, \-\-channel NAME"
124 Apply on channel name.
126 .BR "\-k, \-\-kernel"
127 Apply for the kernel tracer
129 .BR "\-u, \-\-userspace"
130 Apply for the user-space tracer
132 .BR "\-t, \-\-type TYPE"
133 Context type. You can repeat this option on the command line. Please
134 use "lttng add-context \-h" to list all available types.
139 \fBcalibrate\fP [OPTIONS]
141 Quantify LTTng overhead
143 The LTTng calibrate command can be used to find out the combined average
144 overhead of the LTTng tracer and the instrumentation mechanisms used. This
145 overhead can be calibrated in terms of time or using any of the PMU performance
146 counter available on the system.
148 For now, the only calibration implemented is that of the kernel function
149 instrumentation (kretprobes).
151 * Calibrate kernel function instrumentation
153 Let's use an example to show this calibration. We use an i7 processor with 4
154 general-purpose PMU registers. This information is available by issuing dmesg,
155 looking for "generic registers".
157 This sequence of commands will gather a trace executing a kretprobe hooked on
158 an empty function, gathering PMU counters LLC (Last Level Cache) misses
159 information (see lttng add-context \-\-help to see the list of available PMU
163 # lttng create calibrate-function
164 # lttng enable-event calibrate \-\-kernel \\
165 \-\-function lttng_calibrate_kretprobe
166 # lttng add-context \-\-kernel \-t perf:LLC-load-misses \\
167 \-t perf:LLC-store-misses \\
168 \-t perf:LLC-prefetch-misses
170 # for a in $(seq 1 10); do \\
171 lttng calibrate \-\-kernel \-\-function;
174 # babeltrace $(ls \-1drt ~/lttng-traces/calibrate-function-* \\
178 The output from babeltrace can be saved to a text file and opened in a
179 spreadsheet (e.g. oocalc) to focus on the per-PMU counter delta between
180 consecutive "calibrate_entry" and "calibrate_return" events. Note that these
181 counters are per-CPU, so scheduling events would need to be present to account
182 for migration between CPU. Therefore, for calibration purposes, only events
183 staying on the same CPU must be considered.
185 The average result, for the i7, on 10 samples:
189 perf_LLC_load_misses: 5.0 0.577
190 perf_LLC_store_misses: 1.6 0.516
191 perf_LLC_prefetch_misses: 9.0 14.742
194 As we can notice, the load and store misses are relatively stable across runs
195 (their standard deviation is relatively low) compared to the prefetch misses.
196 We can conclude from this information that LLC load and store misses can be
197 accounted for quite precisely, but prefetches within a function seems to behave
198 too erratically (not much causality link between the code executed and the CPU
199 prefetch activity) to be accounted for.
205 Show summary of possible options and commands.
207 .BR "\-k, \-\-kernel"
208 Apply for the kernel tracer
210 .BR "\-u, \-\-userspace"
211 Apply for the user-space tracer
214 Dynamic function entry/return probe (default)
219 \fBcreate\fP [NAME] [OPTIONS]
221 Create tracing session.
223 A tracing session contains channel(s) which contains event(s). It is domain
224 agnostic meaning that you can enable channels and events for either the
225 user-space tracer and/or the kernel tracer. It acts like a container
226 aggregating multiple tracing sources.
228 On creation, a \fB.lttngrc\fP file is created in your $HOME directory
229 containing the current session name. If NAME is omitted, a session name is
230 automatically created having this form: 'auto-yyyymmdd-hhmmss'.
232 If no \fB\-o, \-\-output\fP is specified, the traces will be written in
235 The $HOME environment variable can be overridden by defining the environment
236 variable LTTNG_HOME. This is useful when the user running the commands has
237 a non-writeable home directory.
243 Show summary of possible options and commands.
245 .BR "\-\-list-options"
246 Simple listing of options
248 .BR "\-o, \-\-output PATH"
249 Specify output path for traces
252 Traces will not be outputed
255 Set the session in snapshot mode. Created in no-output mode and uses the
256 URL, if one, as the default snapshot output. Every channel will be set
257 in overwrite mode and with mmap output (splice not supported).
260 .BR "\-U, \-\-set-url=URL"
261 Set URL for the consumer output destination. It is persistent for the
262 session lifetime. Redo the command to change it. This will set both data
263 and control URL for network.
265 .BR "\-C, \-\-ctrl-url=URL"
266 Set control path URL. (Must use -D also)
268 .BR "\-D, \-\-data-url=URL"
269 Set data path URL. (Must use -C also)
271 Using these options, each API call can be controlled individually. For
272 instance, \-C does not enable the consumer automatically. You'll need the \-e
277 proto://[HOST|IP][:PORT1[:PORT2]][/TRACE_PATH]
279 Supported protocols are (proto):
282 Local filesystem full path.
286 This will use the default network transport layer which is TCP for both
287 control (PORT1) and data port (PORT2). The default ports are
288 respectively 5342 and 5343. Note that net[6]:// is not yet supported.
292 Can only be used with -C and -D together
294 NOTE: IPv6 address MUST be enclosed in brackets '[]' (rfc2732)
299 # lttng create -U net://192.168.1.42
301 Uses TCP and default ports for the given destination.
304 # lttng create -U net6://[fe80::f66d:4ff:fe53:d220]
306 Uses TCP, default ports and IPv6.
309 # lttng create s1 -U net://myhost.com:3229
311 Create session s1 and set its consumer to myhost.com on port 3229 for control.
316 \fBdestroy\fP [NAME] [OPTIONS]
318 Teardown tracing session
320 Free memory on the session daemon and tracer side. It's gone!
322 If NAME is omitted, the session name is taken from the .lttngrc file.
328 Show summary of possible options and commands.
333 .BR "\-\-list-options"
334 Simple listing of options
339 \fBenable-channel\fP NAME[,NAME2,...] (\-k | \-u) [OPTIONS]
341 Enable tracing channel
343 To enable an event, you must enable both the event and the channel that
346 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
349 Exactly one of \-k or -u must be specified.
351 It is important to note that if a certain type of buffers is used, the session
352 will be set with that type and all other subsequent channel needs to have the
355 Note that once the session has been started and enabled on the tracer side,
356 it's not possible anymore to enable a new channel for that session.
364 .BR "\-\-list-options"
365 Simple listing of options
367 .BR "\-s, \-\-session NAME"
368 Apply on session name
370 .BR "\-k, \-\-kernel"
371 Apply to the kernel tracer
373 .BR "\-u, \-\-userspace"
374 Apply to the user-space tracer
377 Discard event when subbuffers are full (default)
380 Flight recorder mode : overwrites events when subbuffers are full
382 .BR "\-\-subbuf-size SIZE"
383 Subbuffer size in bytes {+k,+M,+G}.
384 (default UST uid: 131072, UST pid: 4096, kernel: 262144, metadata: 4096)
385 Rounded up to the next power of 2.
387 The minimum subbuffer size, for each tracer, is the max value between
388 the default above and the system page size. You can issue this command
389 to get the current page size on your system: \fB$ getconf PAGE_SIZE\fP
391 .BR "\-\-num-subbuf NUM"
392 Number of subbuffers. (default UST uid: 4, UST pid: 4, kernel: 4,
393 metadata: 2) Rounded up to the next power of 2.
395 .BR "\-\-switch-timer USEC"
396 Switch subbuffer timer interval in µsec.
397 (default UST uid: 0, UST pid: 0, kernel: 0, metadata: 0)
399 .BR "\-\-read-timer USEC"
400 Read timer interval in µsec.
401 (default UST uid: 0, UST pid: 0, kernel: 200000, metadata: 0)
403 .BR "\-\-output TYPE"
404 Channel output type. Possible values: mmap, splice
405 (default UST uid: mmap, UST pid: mmap, kernel: splice, metadata: mmap)
407 .BR "\-\-buffers-uid"
408 Use per UID buffer (\-u only). Buffers are shared between applications
409 that have the same UID.
411 .BR "\-\-buffers-pid"
412 Use per PID buffer (\-u only). Each application has its own buffers.
414 .BR "\-\-buffers-global"
415 Use shared buffer for the whole system (\-k only)
417 .BR "\-C, \-\-tracefile-size SIZE"
418 Maximum size of each tracefile within a stream (in bytes).
419 0 means unlimited. (default: 0)
421 .BR "\-W, \-\-tracefile-count COUNT"
422 Used in conjunction with \-C option, this will limit the number of files
423 created to the specified count. 0 means unlimited. (default: 0)
428 $ lttng enable-channel -k -C 4096 -W 32 chan1
430 For each stream, the maximum size of each trace file will be 4096 bytes, and
431 there will be a maximum of 32 different files. The file count is appended after
432 the stream number as seen in the following example. The last trace file is
433 smaller than 4096 since it was not completely filled.
436 ~/lttng-traces/[...]/chan1_0_0 (4096)
437 ~/lttng-traces/[...]/chan1_0_1 (4096)
438 ~/lttng-traces/[...]/chan1_0_2 (3245)
439 ~/lttng-traces/[...]/chan1_1_0 (4096)
444 $ lttng enable-channel -k -C 4096
446 This will create trace files of 4096 bytes and will create new ones as long as
447 there is data available.
452 \fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]
456 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
457 omitted, a default channel named '\fBchannel0\fP' is created and the event is
458 added to it. If \fB\-c, \-\-channel\fP is omitted, but a non-default
459 channel already exists within the session, an error is returned. For the
460 user-space tracer, using \fB\-a, \-\-all\fP is the same as using the
463 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
470 Show summary of possible options and commands.
472 .BR "\-\-list-options"
473 Simple listing of options
475 .BR "\-s, \-\-session NAME"
476 Apply on session name
478 .BR "\-c, \-\-channel NAME"
479 Apply on channel name
482 Enable all tracepoints and syscalls. This actually enable a single
485 .BR "\-k, \-\-kernel"
486 Apply for the kernel tracer
488 .BR "\-u, \-\-userspace"
489 Apply for the user-space tracer
492 Tracepoint event (default). Userspace tracer supports wildcards at end
493 of string. Don't forget to quote to deal with bash expansion.
500 .BR "\-\-loglevel NAME"
501 Tracepoint loglevel range from 0 to loglevel. Listed in the help (\-h).
503 .BR "\-\-loglevel-only NAME"
504 Tracepoint loglevel (only this loglevel).
505 The loglevel or loglevel-only options should be combined with a
506 tracepoint name or tracepoint wildcard.
508 .BR "\-\-probe (addr | symbol | symbol+offset)"
509 Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
510 or hexadecimal (0xNNN...)
512 .BR "\-\-function (addr | symbol | symbol+offset)"
513 Dynamic function entry/return probe. Addr and offset can be octal
514 (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
517 System call event. Enabling syscalls tracing (kernel tracer), you will
518 not be able to disable them with disable-event. This is a known
519 limitation. You can disable the entire channel to do the trick.
521 .BR "\-\-filter 'expression'"
522 Set a filter on a newly enabled event. Filter expression on event
523 fields and context. Event recording depends on evaluation. Only
524 specify on first activation of a given event within a session.
525 Filter only allowed when enabling events within a session before
526 tracing is started. If the filter fails to link with the event
527 within the traced domain, the event will be discarded.
528 Currently, filter is only implemented for the user-space tracer.
533 'intfield > 500 && intfield < 503'
534 '(strfield == "test" || intfield != 10) && intfield > 33'
535 'doublefield > 1.1 && intfield < 5.3'
538 Wildcards are allowed at the end of strings:
540 In string literals, the escape character is a '\\'. Use '\\*' for
541 the '*' character, and '\\\\' for the '\\' character. Wildcard
542 match any sequence of characters, including an empty sub-string
543 (match 0 or more characters).
545 Context information can be used for filtering. The examples below show
546 usage of context filtering on process name (with a wildcard), process ID
547 range, and unique thread ID for filtering. The process and thread ID of
548 running applications can be found under columns "PID" and "LWP" of the
552 '$ctx.procname == "demo*"'
553 '$ctx.vpid >= 4433 && $ctx.vpid < 4455'
561 \fBdisable-channel\fP NAME[,NAME2,...] (\-k | \-u) [OPTIONS]
563 Disable tracing channel
565 Disabling a channel makes all event(s) in that channel to stop tracing. You can
566 enable it back by calling \fBlttng enable-channel NAME\fP again.
568 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
575 Show summary of possible options and commands.
577 .BR "\-\-list-options"
578 Simple listing of options
580 .BR "\-s, \-\-session NAME"
581 Apply on session name
583 .BR "\-k, \-\-kernel"
584 Apply for the kernel tracer
586 .BR "\-u, \-\-userspace"
587 Apply for the user-space tracer
592 \fBdisable-event\fP NAME[,NAME2,...] (\-k | \-u) [OPTIONS]
594 Disable tracing event
596 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
599 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
602 If \fB\-c, \-\-channel\fP is omitted, the default channel name is used.
603 If \fB\-c, \-\-channel\fP is omitted, but a non-default channel already
604 exists within the session, an error is returned.
610 Show summary of possible options and commands.
612 .BR "\-\-list-options"
613 Simple listing of options
615 .BR "\-s, \-\-session NAME"
616 Apply on session name
618 .BR "\-c, \-\-channel NAME"
619 Apply on channel name
621 .BR "\-a, \-\-all-events"
622 Disable all events. This does NOT disable "*" but rather every known
623 events of the session.
625 .BR "\-k, \-\-kernel"
626 Apply for the kernel tracer
628 .BR "\-u, \-\-userspace"
629 Apply for the user-space tracer
634 \fBlist\fP [OPTIONS] [SESSION [SESSION OPTIONS]]
636 List tracing session information.
638 With no arguments, it will list available tracing session(s).
640 With the session name, it will display the details of the session including
641 the trace file path, the associated channels and their state (activated
642 and deactivated), the activated events and more.
644 With \-k alone, it will list all available kernel events (except the system
646 With \-u alone, it will list all available user-space events from registered
647 applications. Here is an example of 'lttng list \-u':
650 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
651 ust_tests_hello:tptest_sighandler (type: tracepoint)
652 ust_tests_hello:tptest (type: tracepoint)
655 You can now enable any event listed by using the name :
656 \fBust_tests_hello:tptest\fP.
662 Show summary of possible options and commands.
664 .BR "\-\-list-options"
665 Simple listing of options
667 .BR "\-k, \-\-kernel"
670 .BR "\-u, \-\-userspace"
671 Select user-space domain.
677 .BR "\-c, \-\-channel NAME"
678 List details of a channel
680 .BR "\-d, \-\-domain"
681 List available domain(s)
686 \fBset-session\fP NAME [OPTIONS]
688 Set current session name
690 Will change the session name in the .lttngrc file.
696 Show summary of possible options and commands.
698 .BR "\-\-list-options"
699 Simple listing of options
704 \fBsnapshot\fP [OPTIONS] ACTION
706 Snapshot command for LTTng session.
712 Show summary of possible options and commands.
714 .BR "\-\-list-options"
715 Simple listing of options
721 \fBadd-output\fP [-m <SIZE>] [-s <NAME>] [-n <NAME>] <URL> | -C <URL> -D <URL>
723 Setup and add an snapshot output for a session. Output are the destination
724 where the snapshot will be sent. Only one output is permitted. To change it,
725 you'll need to delete it and add back the new one.
728 \fBdel-output\fP ID | NAME [-s <NAME>]
730 Delete an output for a session using the ID. You can either specify the
731 output's ID that can be found with list-output or the name.
734 \fBlist-output\fP [-s <NAME>]
736 List the output of a session. Attributes of the output are printed.
739 \fBrecord\fP [-m <SIZE>] [-s <NAME>] [-n <NAME>] [<URL> | -C <URL> -D <URL>]
741 Snapshot a session's buffer(s) for all domains. If an URL is specified, it is
742 used instead of a previously added output. Specifying only a name or/and a max
743 size will override the current output values. For instance, you can record a
744 snapshot with a custom maximum size or with a different name.
747 $ lttng add-output -n mysnapshot file:///data/snapshot
749 $ lttng snapshot record -n new_name_snapshot
752 The above will create a snapshot in /data/snapshot/new_name_snapshot* directory
753 rather then in mysnapshot*/
756 .B DETAILED ACTION OPTIONS
759 .BR "\-s, \-\-session NAME"
760 Apply to session name.
762 .BR "\-n, \-\-name NAME"
763 Name of the snapshot's output.
765 .BR "\-m, \-\-max-size SIZE"
766 Maximum size in bytes of the snapshot. The maxium size does not include
769 .BR "\-C, \-\-ctrl-url URL"
770 Set control path URL. (Must use -D also)
772 .BR "\-D, \-\-data-url URL"
773 Set data path URL. (Must use -C also)
778 \fBstart\fP [NAME] [OPTIONS]
782 It will start tracing for all tracers for a specific tracing session.
783 If NAME is omitted, the session name is taken from the .lttngrc file.
789 Show summary of possible options and commands.
791 .BR "\-\-list-options"
792 Simple listing of options
797 \fBstop\fP [NAME] [OPTIONS]
801 It will stop tracing for all tracers for a specific tracing session. Before
802 returning, the command checks for data availability meaning that it will wait
803 until the trace is readable for the session. Use \-\-no-wait to avoid this
806 If NAME is omitted, the session name is taken from the .lttngrc file.
812 Show summary of possible options and commands.
814 .BR "\-\-list-options"
815 Simple listing of options
817 Don't wait for data availability.
824 Show version information
830 Show summary of possible options and commands.
832 .BR "\-\-list-options"
833 Simple listing of options
838 \fBview\fP [SESSION_NAME] [OPTIONS]
840 View traces of a tracing session. By default, the babeltrace viewer
841 will be used for text viewing. If SESSION_NAME is omitted, the session
842 name is taken from the .lttngrc file.
850 .BR "\-\-list-options"
851 Simple listing of options
853 .BR "\-t, \-\-trace-path PATH"
854 Trace directory path for the viewer
856 .BR "\-e, \-\-viewer CMD"
857 Specify viewer and/or options to use This will completely override the
858 default viewers so please make sure to specify the full command. The
859 trace directory path of the session will be appended at the end to the
866 On success 0 is returned and a positive value on error. Value of 1 means a command
867 error, 2 an undefined command, 3 a fatal error and 4 a command warning meaning that
868 something went wrong during the command.
870 Any other value above 10, please refer to
871 .BR "<lttng/lttng-error.h>"
872 for a detailed list or use lttng_strerror() to get a human readable string of
876 .SH "ENVIRONMENT VARIABLES"
879 Note that all command line options override environment variables.
883 .IP "LTTNG_SESSIOND_PATH"
884 Allows one to specify the full session daemon binary path to lttng command line
885 tool. You can also use \-\-sessiond-path option having the same effect.
891 .BR lttng-sessiond(8),
893 .BR lttng-health-check(3)
898 If you encounter any issues or usability problem, please report it on our
899 mailing list <lttng-dev@lists.lttng.org> to help improve this project or
900 at https://bugs.lttng.org which is a bugtracker.
906 lttng is distributed under the GNU General Public License version 2. See the file
909 A Web site is available at http://lttng.org for more information on the LTTng
912 You can also find our git tree at http://git.lttng.org.
914 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
916 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
921 Thanks to Yannick Brosseau without whom this project would never have been so
922 lean and mean! Also thanks to the Ericsson teams working on tracing which
923 helped us greatly with detailed bug reports and unusual test cases.
925 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
926 maintainer) and Jon Bernard for our Debian packages.
928 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
929 Montreal for the LTTng journey.
934 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
935 David Goulet. More people have since contributed to it. It is currently
936 maintained by David Goulet <dgoulet@efficios.com>.