Fix: minor changes to lttng.1
[lttng-tools.git] / doc / man / lttng.1
1 .TH "LTTNG" "1" "February 9, 2012" "" ""
2
3 .SH "NAME"
4 lttng \(em LTTng 2.0 tracer control command line tool
5
6 .SH "SYNOPSIS"
7
8 .PP
9 .nf
10 lttng [OPTIONS] <COMMAND>
11 .fi
12 .SH "DESCRIPTION"
13
14 .PP
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.
19
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
23 package.
24
25 LTTng uses a session daemon (lttng-sessiond(8)), acting as a tracing registry,
26 which permits 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.
30
31 In order to trace the kernel, the session daemon needs to be running as root.
32 LTTng provides the use of a \fBtracing group\fP (default: tracing). Whomever is
33 in that group can interact with the root session daemon and thus trace the
34 kernel. Session daemons can co-exist meaning that you can have a session daemon
35 running as Alice that can be used to trace her applications along side with a
36 root daemon or even a Bob daemon. We highly recommend to start the session
37 daemon at boot time for stable and long term tracing.
38
39 Every user-space applications instrumented with lttng-ust(3), will
40 automatically register to the session daemon. This feature gives you the
41 ability to list available traceable applications and tracepoints on a per user
42 basis. (See \fBlist\fP command).
43 .SH "OPTIONS"
44
45 .PP
46 This program follow the usual GNU command line syntax with long options starting with
47 two dashes. Below is a summary of the available options.
48 .PP
49
50 .TP
51 .BR "\-h, \-\-help"
52 Show summary of possible options and commands.
53 .TP
54 .BR "\-v, \-\-verbose"
55 Increase verbosity.
56 Three levels of verbosity are available which are triggered by putting additional v to
57 the option (\-vv or \-vvv)
58 .TP
59 .BR "\-q, \-\-quiet"
60 Suppress all messages (even errors).
61 .TP
62 .BR "\-g, \-\-group NAME"
63 Set unix tracing group name. (default: tracing)
64 .TP
65 .BR "\-n, \-\-no-sessiond"
66 Don't automatically spawn a session daemon.
67 .TP
68 .BR "\-\-sessiond\-path"
69 Set session daemon full binary path.
70 .TP
71 .BR "\-\-list\-options"
72 Simple listing of lttng options.
73 .TP
74 .BR "\-\-list\-commands"
75 Simple listing of lttng commands.
76 .SH "COMMANDS"
77
78 .TP
79 \fBadd-context\fP
80 .nf
81 Add context to event(s) and/or channel(s).
82
83 A context is basically extra information appended to a channel or event. For
84 instance, you could ask the tracer to add the PID information within the
85 "sched_switch" kernel event. You can also add performance monitoring unit
86 counters (perf PMU) using the perf kernel API).
87
88 For example, this command will add the context information 'prio' and two perf
89 counters (hardware branch misses and cache misses), to all events in the trace
90 data output:
91
92 # lttng add-context \-k \-t prio \-t perf:branch-misses \-t perf:cache-misses
93
94 Please take a look at the help (\-h/\-\-help) for a detailed list of available
95 contexts.
96
97 If no channel and no event is given (\-c/\-e), the context is added to all
98 channels (which applies automatically to all events in that channel). Otherwise
99 the context will be added only to the channel (\-c) and/or event (\-e) indicated.
100
101 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
102 file.
103 .fi
104
105 .B OPTIONS:
106
107 .nf
108 \-h, \-\-help
109 Show summary of possible options and commands.
110 \-s, \-\-session NAME
111 Apply on session name.
112 \-c, \-\-channel NAME
113 Apply on channel name.
114 \-e, \-\-event NAME
115 Apply on event name.
116 \-k, \-\-kernel
117 Apply for the kernel tracer
118 \-u, \-\-userspace
119 Apply for the user-space tracer
120 \-t, \-\-type TYPE
121 Context type. You can repeat this option on the command line. Please
122 use "lttng add-context \-h" to list all available types.
123 .fi
124
125 .IP
126
127 .IP "\fBcalibrate\fP"
128 .nf
129 Quantify LTTng overhead
130
131 The LTTng calibrate command can be used to find out the combined average
132 overhead of the LTTng tracer and the instrumentation mechanisms used. This
133 overhead can be calibrated in terms of time or using any of the PMU performance
134 counter available on the system.
135
136 For now, the only calibration implemented is that of the kernel function
137 instrumentation (kretprobes).
138
139 * Calibrate kernel function instrumentation
140
141 Let's use an example to show this calibration. We use an i7 processor with 4
142 general-purpose PMU registers. This information is available by issuing dmesg,
143 looking for "generic registers".
144
145 This sequence of commands will gather a trace executing a kretprobe hooked on
146 an empty function, gathering PMU counters LLC (Last Level Cache) misses
147 information (see lttng add-context \-\-help to see the list of available PMU
148 counters).
149
150 # lttng create calibrate-function
151 # lttng enable-event calibrate \-\-kernel \-\-function lttng_calibrate_kretprobe
152 # lttng add-context \-\-kernel \-t perf:LLC-load-misses \-t perf:LLC-store-misses \\
153 \-t perf:LLC-prefetch-misses
154 # lttng start
155 # for a in $(seq 1 10); do \\
156 lttng calibrate \-\-kernel \-\-function;
157 done
158 # lttng destroy
159 # babeltrace $(ls \-1drt ~/lttng-traces/calibrate-function-* | tail \-n 1)
160
161 The output from babeltrace can be saved to a text file and opened in a
162 spreadsheet (e.g. oocalc) to focus on the per-PMU counter delta between
163 consecutive "calibrate_entry" and "calibrate_return" events. Note that these
164 counters are per-CPU, so scheduling events would need to be present to account
165 for migration between CPU. Therefore, for calibration purposes, only events
166 staying on the same CPU must be considered.
167
168 The average result, for the i7, on 10 samples:
169
170 Average Std.Dev.
171 perf_LLC_load_misses: 5.0 0.577
172 perf_LLC_store_misses: 1.6 0.516
173 perf_LLC_prefetch_misses: 9.0 14.742
174
175 As we can notice, the load and store misses are relatively stable across runs
176 (their standard deviation is relatively low) compared to the prefetch misses.
177 We can conclude from this information that LLC load and store misses can be
178 accounted for quite precisely, but prefetches within a function seems to behave
179 too erratically (not much causality link between the code executed and the CPU
180 prefetch activity) to be accounted for.
181 .fi
182
183 .B OPTIONS:
184
185 .nf
186 \-h, \-\-help
187 Show summary of possible options and commands.
188 \-k, \-\-kernel
189 Apply for the kernel tracer
190 \-u, \-\-userspace
191 Apply for the user-space tracer
192 \-\-function
193 Dynamic function entry/return probe (default)
194 .fi
195
196 .IP
197
198 .IP "\fBcreate\fP [OPTIONS] [NAME]
199 .nf
200 Create tracing session.
201
202 A tracing session contains channel(s) which contains event(s). It is domain
203 agnostic meaning that you can enable channels and events for either the
204 user-space tracer and/or the kernel tracer. It acts like a container
205 aggregating multiple tracing sources.
206
207 On creation, a \fB.lttngrc\fP file is created in your $HOME directory
208 containing the current session name. If NAME is omitted, a session name is
209 automatically created having this form: 'auto-yyyymmdd-hhmmss'.
210
211 If no \fB\-o, \-\-output\fP is specified, the traces will be written in
212 $HOME/lttng-traces.
213 .fi
214
215 .B OPTIONS:
216
217 .nf
218 \-h, \-\-help
219 Show summary of possible options and commands.
220 \-\-list-options
221 Simple listing of options
222 \-o, \-\-output PATH
223 Specify output path for traces
224 .fi
225
226 .IP
227
228 .IP "\fBdestroy\fP [OPTIONS] [NAME]"
229 .nf
230 Teardown tracing session
231
232 Free memory on the session daemon and tracer side. It's gone!
233
234 If NAME is omitted, the session name is taken from the .lttngrc file.
235 .fi
236
237 .B OPTIONS:
238
239 .nf
240 \-h, \-\-help
241 Show summary of possible options and commands.
242 \-\-list-options
243 Simple listing of options
244 .fi
245
246 .IP
247
248 .IP "\fBenable-channel\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
249 .nf
250 Enable tracing channel
251
252 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
253 file.
254 .fi
255
256 .B OPTIONS:
257
258 .nf
259 \-h, \-\-help
260 Show this help
261 \-\-list-options
262 Simple listing of options
263 \-s, \-\-session
264 Apply on session name
265 \-k, \-\-kernel
266 Apply to the kernel tracer
267 \-u, \-\-userspace
268 Apply to the user-space tracer
269
270 \-\-discard
271 Discard event when subbuffers are full (default)
272 \-\-overwrite
273 Flight recorder mode : overwrites events when subbuffers are full
274 \-\-subbuf-size
275 Subbuffer size in bytes (default: 4096, kernel default: 262144)
276 \-\-num-subbuf
277 Number of subbuffers (default: 4)
278 Needs to be a power of 2 for kernel and ust tracers
279 \-\-switch-timer
280 Switch subbuffer timer interval in usec (default: 0)
281 Needs to be a power of 2 for kernel and ust tracers
282 \-\-read-timer
283 Read timer interval in usec (default: 200)
284 .fi
285
286 .IP
287
288 .IP "\fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
289 .nf
290 Enable tracing event
291
292 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
293 omitted, a default channel named '\fBchannel0\fP' is created and the event is
294 added to it. For the user-space tracer, using \fB\-a, \-\-all\fP is the same as
295 using the wildcard "*".
296
297 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
298 file.
299 .fi
300
301 .B OPTIONS:
302
303 .nf
304 \-h, \-\-help
305 Show summary of possible options and commands.
306 \-\-list-options
307 Simple listing of options
308 \-s, \-\-session
309 Apply on session name
310 \-c, \-\-channel
311 Apply on channel name
312 \-a, \-\-all
313 Enable all tracepoints and syscalls
314 \-k, \-\-kernel
315 Apply for the kernel tracer
316 \-u, \-\-userspace
317 Apply for the user-space tracer
318
319 \-\-tracepoint
320 Tracepoint event (default)
321 - userspace tracer supports wildcards at end of string. Don't forget to
322 quote to deal with bash expansion.
323 e.g.:
324 "*"
325 "app_component:na*"
326 \-\-loglevel
327 Tracepoint loglevel
328 \-\-probe [addr | symbol | symbol+offset]
329 Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
330 or hexadecimal (0xNNN...)
331 \-\-function [addr | symbol | symbol+offset]
332 Dynamic function entry/return probe. Addr and offset can be octal
333 (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
334 \-\-syscall
335 System call event
336 Enabling syscalls tracing (kernel tracer), you will not be able to disable them
337 with disable-event. This is a known limitation. You can disable the entire
338 channel to do the trick.
339 .fi
340
341 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
342 .nf
343 Disable tracing channel
344
345 Disabling a channel makes all event(s) in that channel to stop tracing. You can
346 enable it back by calling \fBlttng enable-channel NAME\fP again.
347
348 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
349 file.
350 .fi
351
352 .B OPTIONS:
353
354 .nf
355 \-h, \-\-help
356 Show summary of possible options and commands.
357 \-\-list-options
358 Simple listing of options
359 \-s, \-\-session
360 Apply on session name
361 \-k, \-\-kernel
362 Apply for the kernel tracer
363 \-u, \-\-userspace
364 Apply for the user-space tracer
365 .fi
366
367 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
368 .nf
369 Disable tracing event
370
371 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
372 NAME\fP again.
373
374 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
375 file.
376 .fi
377
378 .B OPTIONS:
379
380 .nf
381 \-h, \-\-help
382 Show summary of possible options and commands.
383 \-\-list-options
384 Simple listing of options
385 \-s, \-\-session
386 Apply on session name
387 \-k, \-\-kernel
388 Apply for the kernel tracer
389 \-u, \-\-userspace
390 Apply for the user-space tracer
391 .fi
392
393 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
394 .nf
395 List tracing session information.
396
397 With no arguments, it will list available tracing session(s).
398
399 With the session name, it will display the details of the session including
400 the trace file path, the associated channels and their state (activated
401 and deactivated), the activated events and more.
402
403 With \-k alone, it will list all available kernel events (except the system
404 calls events).
405 With \-u alone, it will list all available user-space events from registered
406 applications. Here is an example of 'lttng list \-u':
407
408 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
409 ust_tests_hello:tptest_sighandler (type: tracepoint)
410 ust_tests_hello:tptest (type: tracepoint)
411
412 You can now enable any event listed by using the name :
413 \fBust_tests_hello:tptest\fP.
414 .fi
415
416 .B OPTIONS:
417
418 .nf
419 \-h, \-\-help
420 Show summary of possible options and commands.
421 \-\-list-options
422 Simple listing of options
423 \-k, \-\-kernel
424 Select kernel domain
425 \-u, \-\-userspace
426 Select user-space domain.
427
428 Session options:
429 \-c, \-\-channel NAME
430 List details of a channel
431 \-d, \-\-domain
432 List available domain(s)
433 .fi
434
435 .IP "\fBset-session\fP NAME"
436 .nf
437 Set current session name
438
439 Will change the session name in the .lttngrc file.
440 .fi
441
442 .B OPTIONS:
443
444 .nf
445 \-h, \-\-help
446 Show summary of possible options and commands.
447 \-\-list-options
448 Simple listing of options
449 .fi
450
451 .IP
452
453 .IP "\fBstart\fP [OPTIONS] [NAME]"
454 .nf
455 Start tracing
456
457 It will start tracing for all tracers for a specific tracing session.
458
459 If NAME is omitted, the session name is taken from the .lttngrc file.
460 .fi
461
462 .B OPTIONS:
463
464 .nf
465 \-h, \-\-help
466 Show summary of possible options and commands.
467 \-\-list-options
468 Simple listing of options
469 .fi
470
471 .IP
472
473 .IP "\fBstop\fP [OPTIONS] [NAME]"
474 .nf
475 Stop tracing
476
477 It will stop tracing for all tracers for a specific tracing session.
478
479 If NAME is omitted, the session name is taken from the .lttngrc file.
480 .fi
481
482 .B OPTIONS:
483
484 .nf
485 \-h, \-\-help
486 Show summary of possible options and commands.
487 \-\-list-options
488 Simple listing of options
489 .fi
490
491 .IP
492
493 .IP "\fBversion\fP"
494 .nf
495 Show version information
496 .fi
497
498 .B OPTIONS:
499
500 .nf
501 \-h, \-\-help
502 Show summary of possible options and commands.
503 \-\-list-options
504 Simple listing of options
505 .fi
506
507 .IP
508
509 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
510 .nf
511 View traces of a tracing session
512
513 By default, the babeltrace viewer will be used for text viewing.
514
515 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
516
517 .fi
518
519 .B OPTIONS:
520
521 .nf
522 \-h, \-\-help
523 Show this help
524 \-\-list-options
525 Simple listing of options
526 \-t, \-\-trace-path PATH
527 Trace directory path for the viewer
528 \-e, \-\-viewer CMD
529 Specify viewer and/or options to use
530 This will completely override the default viewers so
531 please make sure to specify the full command. The trace
532 directory path of the session will be appended at the end
533 to the arguments
534 .fi
535
536 .SH "EXIT VALUES"
537
538 .IP "0"
539 Success
540
541 .IP "1"
542 Command error
543
544 .IP "2"
545 Undefined command
546
547 .IP "3"
548 Fatal error
549
550 .IP "4"
551 Command warning
552
553 .IP "16"
554 No session found by the name given
555
556 .IP "18"
557 Error in session creation
558
559 .IP "21"
560 Error in application(s) listing
561
562 .IP "28"
563 Session name already exists
564
565 .IP "33"
566 Kernel tracer unavailable
567
568 .IP "35"
569 Kernel event exists
570
571 .IP "37"
572 Kernel channel exists
573
574 .IP "38"
575 Kernel channel creation failed
576
577 .IP "39"
578 Kernel channel not found
579
580 .IP "40"
581 Kernel channel disable failed
582
583 .IP "41"
584 Kernel channel enable failed
585
586 .IP "42"
587 Kernel context failed
588
589 .IP "43"
590 Kernel enable event failed
591
592 .IP "44"
593 Kernel disable event failed
594
595 .IP "53"
596 Kernel listing events failed
597
598 .IP "60"
599 UST channel disable failed
600
601 .IP "61"
602 UST channel enable failed
603
604 .IP "62"
605 UST adding context failed
606
607 .IP "63"
608 UST event enable failed
609
610 .IP "64"
611 UST event disable failed
612
613 .IP "66"
614 UST start failed
615
616 .IP "67"
617 UST stop failed
618
619 .IP "75"
620 UST event exists
621
622 .IP "76"
623 UST event not found
624
625 .IP "77"
626 UST context exists
627
628 .IP "78"
629 UST invalid context
630
631 .IP "79"
632 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
633 user membership.
634
635 .IP "80"
636 Tracing already started
637
638 .IP "81"
639 Tracing already stopped
640 .PP
641 .SH "ENVIRONMENT VARIABLES"
642
643 .PP
644 Note that all command line options override environment variables.
645 .PP
646
647 .PP
648 .IP "LTTNG_SESSIOND_PATH_ENV"
649 Allows one to specify the full session daemon binary path to lttng command line
650 tool. You can also use \-\-sessiond-path option having the same effect.
651 .SH "SEE ALSO"
652
653 .PP
654 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
655 .PP
656 .SH "BUGS"
657
658 .PP
659 No show stopper bugs are known yet in this version.
660
661 If you encounter any issues or usability problem, please report it on our
662 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
663 .SH "CREDITS"
664
665 .PP
666 lttng is distributed under the GNU General Public License version 2. See the file
667 COPYING for details.
668 .PP
669 A Web site is available at http://lttng.org for more information on the LTTng
670 project.
671 .PP
672 You can also find our git tree at http://git.lttng.org.
673 .PP
674 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
675 .PP
676 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
677 .PP
678 .SH "THANKS"
679
680 .PP
681 Thanks to Yannick Brosseau without whom this project would never have been so
682 lean and mean! Also thanks to the Ericsson teams working on tracing which
683 helped us greatly with detailed bug reports and unusual test cases.
684
685 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
686 maintainer) and Jon Bernard for our Debian packages.
687
688 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
689 Montreal for the LTTng journey.
690 .PP
691 .SH "AUTHORS"
692
693 .PP
694 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
695 David Goulet. More people have since contributed to it. It is currently
696 maintained by David Goulet <dgoulet@efficios.com>.
697 .PP
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