1 .TH "LTTNG" "1" "December 3rd, 2012" "" ""
4 lttng \(em LTTng 2.1.x tracer control command line tool
10 lttng [OPTIONS] <COMMAND>
15 The LTTng project aims at providing highly efficient tracing tools for Linux.
16 It's tracers help tracking down performance issues and debugging problems
17 involving multiple concurrent processes and threads. Tracing across multiple
18 systems is also possible.
20 The \fBlttng\fP command line tool from the lttng-tools package is used to control
21 both kernel and user-space tracing. Every interactions with the tracer should
22 be done by this tool or by the liblttng-ctl provided with the lttng-tools
25 LTTng uses a session daemon (lttng-sessiond(8)), acting as a tracing registry,
26 which allows you to interact with multiple tracers (kernel and user-space)
27 inside the same container, a tracing session. Traces can be gathered from the
28 kernel and/or instrumented applications (lttng-ust(3)). Aggregating and reading
29 those traces is done using the babeltrace(1) text viewer.
31 We introduce the notion of \fBtracing domains\fP which is essentially a type of
32 tracer (kernel or user space for now). In the future, we could see a third
33 tracer being for instance an hypervisor. For some commands, you'll need to
34 specify on which domain the command applies (-u or -k). For instance, enabling
35 a kernel event, you must specify the kernel domain to the command so we know
36 for which tracer this event is for.
38 In order to trace the kernel, the session daemon needs to be running as root.
39 LTTng provides the use of a \fBtracing group\fP (default: tracing). Whomever is
40 in that group can interact with the root session daemon and thus trace the
41 kernel. Session daemons can co-exist meaning that you can have a session daemon
42 running as Alice that can be used to trace her applications along side with a
43 root daemon or even a Bob daemon. We highly recommend to start the session
44 daemon at boot time for stable and long term tracing.
46 Every user-space applications instrumented with lttng-ust(3), will
47 automatically register to the session daemon. This feature gives you the
48 ability to list available traceable applications and tracepoints on a per user
49 basis. (See \fBlist\fP command).
53 This program follow the usual GNU command line syntax with long options starting with
54 two dashes. Below is a summary of the available options.
59 Show summary of possible options and commands.
61 .BR "\-v, \-\-verbose"
63 Three levels of verbosity are available which are triggered by putting additional v to
64 the option (\-vv or \-vvv)
67 Suppress all messages (even errors).
69 .BR "\-g, \-\-group NAME"
70 Set unix tracing group name. (default: tracing)
72 .BR "\-n, \-\-no-sessiond"
73 Don't automatically spawn a session daemon.
75 .BR "\-\-sessiond\-path PATH"
76 Set session daemon full binary path.
78 .BR "\-\-list\-options"
79 Simple listing of lttng options.
81 .BR "\-\-list\-commands"
82 Simple listing of lttng commands.
88 Add context to event(s) and/or channel(s).
90 A context is basically extra information appended to a channel. For instance,
91 you could ask the tracer to add the PID information for all events in a
92 channel. You can also add performance monitoring unit counters (perf PMU) using
95 For example, this command will add the context information 'prio' and two perf
96 counters (hardware branch misses and cache misses), to all events in the trace
99 # lttng add-context \-k \-t prio \-t perf:branch-misses \-t perf:cache-misses
101 Please take a look at the help (\-h/\-\-help) for a detailed list of available
104 If no channel is given (\-c), the context is added to all channels. Otherwise
105 the context will be added only to the given channel (\-c).
107 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
115 Show summary of possible options and commands.
116 \-s, \-\-session NAME
117 Apply on session name.
118 \-c, \-\-channel NAME
119 Apply on channel name.
121 Apply for the kernel tracer
123 Apply for the user-space tracer
125 Context type. You can repeat this option on the command line. Please
126 use "lttng add-context \-h" to list all available types.
131 .IP "\fBcalibrate\fP"
133 Quantify LTTng overhead
135 The LTTng calibrate command can be used to find out the combined average
136 overhead of the LTTng tracer and the instrumentation mechanisms used. This
137 overhead can be calibrated in terms of time or using any of the PMU performance
138 counter available on the system.
140 For now, the only calibration implemented is that of the kernel function
141 instrumentation (kretprobes).
143 * Calibrate kernel function instrumentation
145 Let's use an example to show this calibration. We use an i7 processor with 4
146 general-purpose PMU registers. This information is available by issuing dmesg,
147 looking for "generic registers".
149 This sequence of commands will gather a trace executing a kretprobe hooked on
150 an empty function, gathering PMU counters LLC (Last Level Cache) misses
151 information (see lttng add-context \-\-help to see the list of available PMU
154 # lttng create calibrate-function
155 # lttng enable-event calibrate \-\-kernel \-\-function lttng_calibrate_kretprobe
156 # lttng add-context \-\-kernel \-t perf:LLC-load-misses \-t perf:LLC-store-misses \\
157 \-t perf:LLC-prefetch-misses
159 # for a in $(seq 1 10); do \\
160 lttng calibrate \-\-kernel \-\-function;
163 # babeltrace $(ls \-1drt ~/lttng-traces/calibrate-function-* | tail \-n 1)
165 The output from babeltrace can be saved to a text file and opened in a
166 spreadsheet (e.g. oocalc) to focus on the per-PMU counter delta between
167 consecutive "calibrate_entry" and "calibrate_return" events. Note that these
168 counters are per-CPU, so scheduling events would need to be present to account
169 for migration between CPU. Therefore, for calibration purposes, only events
170 staying on the same CPU must be considered.
172 The average result, for the i7, on 10 samples:
175 perf_LLC_load_misses: 5.0 0.577
176 perf_LLC_store_misses: 1.6 0.516
177 perf_LLC_prefetch_misses: 9.0 14.742
179 As we can notice, the load and store misses are relatively stable across runs
180 (their standard deviation is relatively low) compared to the prefetch misses.
181 We can conclude from this information that LLC load and store misses can be
182 accounted for quite precisely, but prefetches within a function seems to behave
183 too erratically (not much causality link between the code executed and the CPU
184 prefetch activity) to be accounted for.
191 Show summary of possible options and commands.
193 Apply for the kernel tracer
195 Apply for the user-space tracer
197 Dynamic function entry/return probe (default)
202 .IP "\fBcreate\fP [NAME] [OPTIONS]
204 Create tracing session.
206 A tracing session contains channel(s) which contains event(s). It is domain
207 agnostic meaning that you can enable channels and events for either the
208 user-space tracer and/or the kernel tracer. It acts like a container
209 aggregating multiple tracing sources.
211 On creation, a \fB.lttngrc\fP file is created in your $HOME directory
212 containing the current session name. If NAME is omitted, a session name is
213 automatically created having this form: 'auto-yyyymmdd-hhmmss'.
215 If no \fB\-o, \-\-output\fP is specified, the traces will be written in
223 Show summary of possible options and commands.
225 Simple listing of options
227 Specify output path for traces
229 Using these options, each API call can be controlled individually. For
230 instance, \-C does not enable the consumer automatically. You'll need the \-e
234 Set URL for the enable-consumer destination. It is persistent for the
235 session lifetime. Redo the command to change it. This will set both
236 data and control URL for network.
237 \-C, \-\-ctrl-url=URL
238 Set control path URL. (Must use -D also)
239 \-D, \-\-data-url=URL
240 Set data path URL. (Must use -C also)
242 Don't activate a consumer for this session.
244 Disable consumer for this session.
246 See \fBenable-consumer\fP command below for the supported URL format.
250 # lttng create -U net://192.168.1.42
251 Uses TCP and default ports for the given destination.
253 # lttng create -U net6://[fe80::f66d:4ff:fe53:d220]
254 Uses TCP, default ports and IPv6.
256 # lttng create s1 -U net://myhost.com:3229
257 Create session s1 and set its consumer to myhost.com on port 3229 for control.
262 .IP "\fBdestroy\fP [OPTIONS] [NAME]"
264 Teardown tracing session
266 Free memory on the session daemon and tracer side. It's gone!
268 If NAME is omitted, the session name is taken from the .lttngrc file.
275 Show summary of possible options and commands.
279 Simple listing of options
284 .IP "\fBenable-channel\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
286 Enable tracing channel
288 To enable an event, you must enable both the event and the channel that
291 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
301 Simple listing of options
302 \-s, \-\-session NAME
303 Apply on session name
305 Apply to the kernel tracer
307 Apply to the user-space tracer
310 Discard event when subbuffers are full (default)
312 Flight recorder mode : overwrites events when subbuffers are full
314 Subbuffer size in bytes (default: 4096, kernel default: 262144)
315 Needs to be a power of 2 for both tracers
317 Number of subbuffers (default: 4)
318 Needs to be a power of 2 for both tracers
319 \-\-switch-timer USEC
320 Switch subbuffer timer interval in µsec (default: 0)
322 Read timer interval in µsec (default: 200)
324 Channel output type. Possible values: mmap, splice
329 .IP "\fBenable-consumer\fP [-u|-k] [URL] [OPTIONS]"
331 Enable a consumer for the tracing session and domain.
333 By default, every tracing session has a consumer attached to it using the local
334 filesystem as output. The trace is written in $HOME/lttng-traces. This command
335 allows the user to specify a specific URL after the session was created for a
336 specific domain. If no domain is specified, the consumer is applied on all
339 Without options, the behavior is to enable a consumer to the current URL. The
340 default URL is the local filesystem at the path of the session mentioned above.
342 The enable-consumer feature supports both local and network transport. You must
343 have a running \fBlttng-relayd(8)\fP for network transmission or any other daemon
344 that can understand the streaming protocol of LTTng.
351 Show summary of possible options and commands.
353 Simple listing of options
354 \-s, \-\-session NAME
355 Apply on session name
357 Apply for the kernel tracer
359 Apply for the user-space tracer
361 Using these options, each API call can be controlled individually. For
362 instance, \-C does not enable the consumer automatically. You'll need the \-e
366 Set URL for the enable-consumer destination. It is persistent for the
367 session lifetime. Redo the command to change it. This will set both
368 data and control URL for network.
369 \-C, \-\-ctrl-url=URL
370 Set control path URL. (Must use -D also)
371 \-D, \-\-data-url=URL
372 Set data path URL. (Must use -C also)
378 proto://[HOST|IP][:PORT1[:PORT2]][/TRACE_PATH]
380 Supported protocols are (proto):
382 Local filesystem full path.
385 This will use the default network transport layer which is TCP for both
386 control (PORT1) and data port (PORT2). The default ports are
387 respectively 5342 and 5343. Note that net[6]:// is not yet supported.
390 Can only be used with -C and -D together
392 NOTE: IPv6 address MUST be enclosed in brackets '[]' (rfc2732)
396 $ lttng enable-consumer -u net://192.168.1.42
398 Uses TCP and default ports for user space tracing (-u) where the IP address
399 above is the destination machine where the traces will be streamed and a
400 \fBlttng-relayd(8)\fP is listening.
403 .IP "\fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
407 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
408 omitted, a default channel named '\fBchannel0\fP' is created and the event is
409 added to it. For the user-space tracer, using \fB\-a, \-\-all\fP is the same as
410 using the wildcard "*".
412 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
420 Show summary of possible options and commands.
422 Simple listing of options
423 \-s, \-\-session NAME
424 Apply on session name
425 \-c, \-\-channel NAME
426 Apply on channel name
428 Enable all tracepoints and syscalls. This actually enable a single
431 Apply for the kernel tracer
433 Apply for the user-space tracer
436 Tracepoint event (default)
437 - userspace tracer supports wildcards at end of string. Don't forget to
438 quote to deal with bash expansion.
443 Tracepoint loglevel range from 0 to loglevel. Listed in the help (\-h).
444 \-\-loglevel-only NAME
445 Tracepoint loglevel (only this loglevel).
447 The loglevel or loglevel-only options should be combined with a
448 tracepoint name or tracepoint wildcard.
449 \-\-probe [addr | symbol | symbol+offset]
450 Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
451 or hexadecimal (0xNNN...)
452 \-\-function [addr | symbol | symbol+offset]
453 Dynamic function entry/return probe. Addr and offset can be octal
454 (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
456 System call event. Enabling syscalls tracing (kernel tracer), you will
457 not be able to disable them with disable-event. This is a known
458 limitation. You can disable the entire channel to do the trick.
460 \-\-filter 'expression'
461 Set a filter on a newly enabled event. Filter expression on event
462 fields, event recording depends on evaluation. Only specify on first
463 activation of a given event within a session. Filter only allowed when
464 enabling events within a session before tracing is started. If the
465 filter fails to link with the event within the traced domain, the event
466 will be discarded. Currently, filter is only implemented for the
471 'intfield > 500 && intfield < 503'
472 '(stringfield == "test" || intfield != 10) && intfield > 33'
473 'doublefield > 1.1 && intfield < 5.3'
475 Wildcards are allowed at the end of strings:
477 In string literals, the escape character is a '\\'. Use '\\*' for
478 the '*' character, and '\\\\' for the '\\' character.
481 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
483 Disable tracing channel
485 Disabling a channel makes all event(s) in that channel to stop tracing. You can
486 enable it back by calling \fBlttng enable-channel NAME\fP again.
488 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
496 Show summary of possible options and commands.
498 Simple listing of options
499 \-s, \-\-session NAME
500 Apply on session name
502 Apply for the kernel tracer
504 Apply for the user-space tracer
507 .IP "\fBdisable-consumer\fP [\-k|\-u] [OPTIONS]"
509 Disable the consumer of a tracing session.
511 This call MUST be done BEFORE tracing has started.
518 Show summary of possible options and commands.
520 Simple listing of options
521 \-s, \-\-session NAME
522 Apply on session name
524 Apply for the kernel tracer
526 Apply for the user-space tracer
529 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
531 Disable tracing event
533 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
536 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
544 Show summary of possible options and commands.
546 Simple listing of options
547 \-s, \-\-session NAME
548 Apply on session name
550 Disable all events. This does NOT disable "*" but rather
551 every known events of the session.
553 Apply for the kernel tracer
555 Apply for the user-space tracer
558 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
560 List tracing session information.
562 With no arguments, it will list available tracing session(s).
564 With the session name, it will display the details of the session including
565 the trace file path, the associated channels and their state (activated
566 and deactivated), the activated events and more.
568 With \-k alone, it will list all available kernel events (except the system
570 With \-u alone, it will list all available user-space events from registered
571 applications. Here is an example of 'lttng list \-u':
573 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
574 ust_tests_hello:tptest_sighandler (type: tracepoint)
575 ust_tests_hello:tptest (type: tracepoint)
577 You can now enable any event listed by using the name :
578 \fBust_tests_hello:tptest\fP.
585 Show summary of possible options and commands.
587 Simple listing of options
591 Select user-space domain.
595 \-c, \-\-channel NAME
596 List details of a channel
598 List available domain(s)
601 .IP "\fBset-session\fP NAME"
603 Set current session name
605 Will change the session name in the .lttngrc file.
612 Show summary of possible options and commands.
614 Simple listing of options
619 .IP "\fBstart\fP [NAME] [OPTIONS]"
623 It will start tracing for all tracers for a specific tracing session.
625 If NAME is omitted, the session name is taken from the .lttngrc file.
632 Show summary of possible options and commands.
634 Simple listing of options
639 .IP "\fBstop\fP [NAME] [OPTIONS]"
643 It will stop tracing for all tracers for a specific tracing session. Before
644 returning, the command checks for data availability meaning that it will wait
645 until the trace is readable for the session. Use \-\-no-wait to avoid this
648 If NAME is omitted, the session name is taken from the .lttngrc file.
655 Show summary of possible options and commands.
657 Simple listing of options
659 Don't wait for data availability.
666 Show version information
673 Show summary of possible options and commands.
675 Simple listing of options
680 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
682 View traces of a tracing session
684 By default, the babeltrace viewer will be used for text viewing.
686 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
696 Simple listing of options
697 \-t, \-\-trace-path PATH
698 Trace directory path for the viewer
700 Specify viewer and/or options to use
701 This will completely override the default viewers so
702 please make sure to specify the full command. The trace
703 directory path of the session will be appended at the end
708 On success 0 is returned and a positive value on error. Value of 1 means a command
709 error, 2 an undefined command, 3 a fatal error and 4 a command warning meaning that
710 something went wrong during the command.
712 Any other value above 10, please refer to
713 .BR <lttng/lttng-error.h>
714 for a detailed list or use lttng_strerror() to get a human readable string of
718 .SH "ENVIRONMENT VARIABLES"
721 Note that all command line options override environment variables.
725 .IP "LTTNG_SESSIOND_PATH"
726 Allows one to specify the full session daemon binary path to lttng command line
727 tool. You can also use \-\-sessiond-path option having the same effect.
731 .BR lttng-sessiond(8),
733 .BR lttng-health-check(3)
736 If you encounter any issues or usability problem, please report it on our
737 mailing list <lttng-dev@lists.lttng.org> to help improve this project or
738 at https://bugs.lttng.org which is a bugtracker.
742 lttng is distributed under the GNU General Public License version 2. See the file
745 A Web site is available at http://lttng.org for more information on the LTTng
748 You can also find our git tree at http://git.lttng.org.
750 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
752 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
757 Thanks to Yannick Brosseau without whom this project would never have been so
758 lean and mean! Also thanks to the Ericsson teams working on tracing which
759 helped us greatly with detailed bug reports and unusual test cases.
761 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
762 maintainer) and Jon Bernard for our Debian packages.
764 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
765 Montreal for the LTTng journey.
770 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
771 David Goulet. More people have since contributed to it. It is currently
772 maintained by David Goulet <dgoulet@efficios.com>.