Fix: add small detail to enable-channel man page
[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 To enable event, you must first enable a channel which contains event(s).
253
254 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
255 file.
256 .fi
257
258 .B OPTIONS:
259
260 .nf
261 \-h, \-\-help
262 Show this help
263 \-\-list-options
264 Simple listing of options
265 \-s, \-\-session
266 Apply on session name
267 \-k, \-\-kernel
268 Apply to the kernel tracer
269 \-u, \-\-userspace
270 Apply to the user-space tracer
271
272 \-\-discard
273 Discard event when subbuffers are full (default)
274 \-\-overwrite
275 Flight recorder mode : overwrites events when subbuffers are full
276 \-\-subbuf-size
277 Subbuffer size in bytes (default: 4096, kernel default: 262144)
278 \-\-num-subbuf
279 Number of subbuffers (default: 4)
280 Needs to be a power of 2 for kernel and ust tracers
281 \-\-switch-timer
282 Switch subbuffer timer interval in usec (default: 0)
283 Needs to be a power of 2 for kernel and ust tracers
284 \-\-read-timer
285 Read timer interval in usec (default: 200)
286 .fi
287
288 .IP
289
290 .IP "\fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
291 .nf
292 Enable tracing event
293
294 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
295 omitted, a default channel named '\fBchannel0\fP' is created and the event is
296 added to it. For the user-space tracer, using \fB\-a, \-\-all\fP is the same as
297 using the wildcard "*".
298
299 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
300 file.
301 .fi
302
303 .B OPTIONS:
304
305 .nf
306 \-h, \-\-help
307 Show summary of possible options and commands.
308 \-\-list-options
309 Simple listing of options
310 \-s, \-\-session
311 Apply on session name
312 \-c, \-\-channel
313 Apply on channel name
314 \-a, \-\-all
315 Enable all tracepoints and syscalls
316 \-k, \-\-kernel
317 Apply for the kernel tracer
318 \-u, \-\-userspace
319 Apply for the user-space tracer
320
321 \-\-tracepoint
322 Tracepoint event (default)
323 - userspace tracer supports wildcards at end of string. Don't forget to
324 quote to deal with bash expansion.
325 e.g.:
326 "*"
327 "app_component:na*"
328 \-\-loglevel
329 Tracepoint loglevel
330 \-\-probe [addr | symbol | symbol+offset]
331 Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
332 or hexadecimal (0xNNN...)
333 \-\-function [addr | symbol | symbol+offset]
334 Dynamic function entry/return probe. Addr and offset can be octal
335 (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
336 \-\-syscall
337 System call event
338 Enabling syscalls tracing (kernel tracer), you will not be able to disable them
339 with disable-event. This is a known limitation. You can disable the entire
340 channel to do the trick.
341 .fi
342
343 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
344 .nf
345 Disable tracing channel
346
347 Disabling a channel makes all event(s) in that channel to stop tracing. You can
348 enable it back by calling \fBlttng enable-channel NAME\fP again.
349
350 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
351 file.
352 .fi
353
354 .B OPTIONS:
355
356 .nf
357 \-h, \-\-help
358 Show summary of possible options and commands.
359 \-\-list-options
360 Simple listing of options
361 \-s, \-\-session
362 Apply on session name
363 \-k, \-\-kernel
364 Apply for the kernel tracer
365 \-u, \-\-userspace
366 Apply for the user-space tracer
367 .fi
368
369 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
370 .nf
371 Disable tracing event
372
373 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
374 NAME\fP again.
375
376 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
377 file.
378 .fi
379
380 .B OPTIONS:
381
382 .nf
383 \-h, \-\-help
384 Show summary of possible options and commands.
385 \-\-list-options
386 Simple listing of options
387 \-s, \-\-session
388 Apply on session name
389 \-k, \-\-kernel
390 Apply for the kernel tracer
391 \-u, \-\-userspace
392 Apply for the user-space tracer
393 .fi
394
395 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
396 .nf
397 List tracing session information.
398
399 With no arguments, it will list available tracing session(s).
400
401 With the session name, it will display the details of the session including
402 the trace file path, the associated channels and their state (activated
403 and deactivated), the activated events and more.
404
405 With \-k alone, it will list all available kernel events (except the system
406 calls events).
407 With \-u alone, it will list all available user-space events from registered
408 applications. Here is an example of 'lttng list \-u':
409
410 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
411 ust_tests_hello:tptest_sighandler (type: tracepoint)
412 ust_tests_hello:tptest (type: tracepoint)
413
414 You can now enable any event listed by using the name :
415 \fBust_tests_hello:tptest\fP.
416 .fi
417
418 .B OPTIONS:
419
420 .nf
421 \-h, \-\-help
422 Show summary of possible options and commands.
423 \-\-list-options
424 Simple listing of options
425 \-k, \-\-kernel
426 Select kernel domain
427 \-u, \-\-userspace
428 Select user-space domain.
429
430 Session options:
431 \-c, \-\-channel NAME
432 List details of a channel
433 \-d, \-\-domain
434 List available domain(s)
435 .fi
436
437 .IP "\fBset-session\fP NAME"
438 .nf
439 Set current session name
440
441 Will change the session name in the .lttngrc file.
442 .fi
443
444 .B OPTIONS:
445
446 .nf
447 \-h, \-\-help
448 Show summary of possible options and commands.
449 \-\-list-options
450 Simple listing of options
451 .fi
452
453 .IP
454
455 .IP "\fBstart\fP [OPTIONS] [NAME]"
456 .nf
457 Start tracing
458
459 It will start tracing for all tracers for a specific tracing session.
460
461 If NAME is omitted, the session name is taken from the .lttngrc file.
462 .fi
463
464 .B OPTIONS:
465
466 .nf
467 \-h, \-\-help
468 Show summary of possible options and commands.
469 \-\-list-options
470 Simple listing of options
471 .fi
472
473 .IP
474
475 .IP "\fBstop\fP [OPTIONS] [NAME]"
476 .nf
477 Stop tracing
478
479 It will stop tracing for all tracers for a specific tracing session.
480
481 If NAME is omitted, the session name is taken from the .lttngrc file.
482 .fi
483
484 .B OPTIONS:
485
486 .nf
487 \-h, \-\-help
488 Show summary of possible options and commands.
489 \-\-list-options
490 Simple listing of options
491 .fi
492
493 .IP
494
495 .IP "\fBversion\fP"
496 .nf
497 Show version information
498 .fi
499
500 .B OPTIONS:
501
502 .nf
503 \-h, \-\-help
504 Show summary of possible options and commands.
505 \-\-list-options
506 Simple listing of options
507 .fi
508
509 .IP
510
511 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
512 .nf
513 View traces of a tracing session
514
515 By default, the babeltrace viewer will be used for text viewing.
516
517 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
518
519 .fi
520
521 .B OPTIONS:
522
523 .nf
524 \-h, \-\-help
525 Show this help
526 \-\-list-options
527 Simple listing of options
528 \-t, \-\-trace-path PATH
529 Trace directory path for the viewer
530 \-e, \-\-viewer CMD
531 Specify viewer and/or options to use
532 This will completely override the default viewers so
533 please make sure to specify the full command. The trace
534 directory path of the session will be appended at the end
535 to the arguments
536 .fi
537
538 .SH "EXIT VALUES"
539
540 .IP "0"
541 Success
542
543 .IP "1"
544 Command error
545
546 .IP "2"
547 Undefined command
548
549 .IP "3"
550 Fatal error
551
552 .IP "4"
553 Command warning
554
555 .IP "16"
556 No session found by the name given
557
558 .IP "18"
559 Error in session creation
560
561 .IP "21"
562 Error in application(s) listing
563
564 .IP "28"
565 Session name already exists
566
567 .IP "33"
568 Kernel tracer unavailable
569
570 .IP "35"
571 Kernel event exists
572
573 .IP "37"
574 Kernel channel exists
575
576 .IP "38"
577 Kernel channel creation failed
578
579 .IP "39"
580 Kernel channel not found
581
582 .IP "40"
583 Kernel channel disable failed
584
585 .IP "41"
586 Kernel channel enable failed
587
588 .IP "42"
589 Kernel context failed
590
591 .IP "43"
592 Kernel enable event failed
593
594 .IP "44"
595 Kernel disable event failed
596
597 .IP "53"
598 Kernel listing events failed
599
600 .IP "60"
601 UST channel disable failed
602
603 .IP "61"
604 UST channel enable failed
605
606 .IP "62"
607 UST adding context failed
608
609 .IP "63"
610 UST event enable failed
611
612 .IP "64"
613 UST event disable failed
614
615 .IP "66"
616 UST start failed
617
618 .IP "67"
619 UST stop failed
620
621 .IP "75"
622 UST event exists
623
624 .IP "76"
625 UST event not found
626
627 .IP "77"
628 UST context exists
629
630 .IP "78"
631 UST invalid context
632
633 .IP "79"
634 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
635 user membership.
636
637 .IP "80"
638 Tracing already started
639
640 .IP "81"
641 Tracing already stopped
642 .PP
643 .SH "ENVIRONMENT VARIABLES"
644
645 .PP
646 Note that all command line options override environment variables.
647 .PP
648
649 .PP
650 .IP "LTTNG_SESSIOND_PATH_ENV"
651 Allows one to specify the full session daemon binary path to lttng command line
652 tool. You can also use \-\-sessiond-path option having the same effect.
653 .SH "SEE ALSO"
654
655 .PP
656 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
657 .PP
658 .SH "BUGS"
659
660 .PP
661 No show stopper bugs are known yet in this version.
662
663 If you encounter any issues or usability problem, please report it on our
664 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
665 .SH "CREDITS"
666
667 .PP
668 lttng is distributed under the GNU General Public License version 2. See the file
669 COPYING for details.
670 .PP
671 A Web site is available at http://lttng.org for more information on the LTTng
672 project.
673 .PP
674 You can also find our git tree at http://git.lttng.org.
675 .PP
676 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
677 .PP
678 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
679 .PP
680 .SH "THANKS"
681
682 .PP
683 Thanks to Yannick Brosseau without whom this project would never have been so
684 lean and mean! Also thanks to the Ericsson teams working on tracing which
685 helped us greatly with detailed bug reports and unusual test cases.
686
687 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
688 maintainer) and Jon Bernard for our Debian packages.
689
690 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
691 Montreal for the LTTng journey.
692 .PP
693 .SH "AUTHORS"
694
695 .PP
696 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
697 David Goulet. More people have since contributed to it. It is currently
698 maintained by David Goulet <dgoulet@efficios.com>.
699 .PP
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