Fix: enable event with different loglevel error
[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 \-a, \-\-all
243 Destroy all sessions
244 \-\-list-options
245 Simple listing of options
246 .fi
247
248 .IP
249
250 .IP "\fBenable-channel\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
251 .nf
252 Enable tracing channel
253
254 To enable event, you must first enable a channel which contains event(s).
255
256 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
257 file.
258 .fi
259
260 .B OPTIONS:
261
262 .nf
263 \-h, \-\-help
264 Show this help
265 \-\-list-options
266 Simple listing of options
267 \-s, \-\-session
268 Apply on session name
269 \-k, \-\-kernel
270 Apply to the kernel tracer
271 \-u, \-\-userspace
272 Apply to the user-space tracer
273
274 \-\-discard
275 Discard event when subbuffers are full (default)
276 \-\-overwrite
277 Flight recorder mode : overwrites events when subbuffers are full
278 \-\-subbuf-size
279 Subbuffer size in bytes (default: 4096, kernel default: 262144)
280 \-\-num-subbuf
281 Number of subbuffers (default: 4)
282 Needs to be a power of 2 for kernel and ust tracers
283 \-\-switch-timer
284 Switch subbuffer timer interval in usec (default: 0)
285 Needs to be a power of 2 for kernel and ust tracers
286 \-\-read-timer
287 Read timer interval in usec (default: 200)
288 .fi
289
290 .IP
291
292 .IP "\fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
293 .nf
294 Enable tracing event
295
296 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
297 omitted, a default channel named '\fBchannel0\fP' is created and the event is
298 added to it. For the user-space tracer, using \fB\-a, \-\-all\fP is the same as
299 using the wildcard "*".
300
301 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
302 file.
303 .fi
304
305 .B OPTIONS:
306
307 .nf
308 \-h, \-\-help
309 Show summary of possible options and commands.
310 \-\-list-options
311 Simple listing of options
312 \-s, \-\-session
313 Apply on session name
314 \-c, \-\-channel
315 Apply on channel name
316 \-a, \-\-all
317 Enable all tracepoints and syscalls
318 \-k, \-\-kernel
319 Apply for the kernel tracer
320 \-u, \-\-userspace
321 Apply for the user-space tracer
322
323 \-\-tracepoint
324 Tracepoint event (default)
325 - userspace tracer supports wildcards at end of string. Don't forget to
326 quote to deal with bash expansion.
327 e.g.:
328 "*"
329 "app_component:na*"
330 \-\-loglevel
331 Tracepoint loglevel
332 \-\-probe [addr | symbol | symbol+offset]
333 Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
334 or hexadecimal (0xNNN...)
335 \-\-function [addr | symbol | symbol+offset]
336 Dynamic function entry/return probe. Addr and offset can be octal
337 (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
338 \-\-syscall
339 System call event
340 Enabling syscalls tracing (kernel tracer), you will not be able to disable them
341 with disable-event. This is a known limitation. You can disable the entire
342 channel to do the trick.
343 .fi
344
345 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
346 .nf
347 Disable tracing channel
348
349 Disabling a channel makes all event(s) in that channel to stop tracing. You can
350 enable it back by calling \fBlttng enable-channel NAME\fP again.
351
352 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
353 file.
354 .fi
355
356 .B OPTIONS:
357
358 .nf
359 \-h, \-\-help
360 Show summary of possible options and commands.
361 \-\-list-options
362 Simple listing of options
363 \-s, \-\-session
364 Apply on session name
365 \-k, \-\-kernel
366 Apply for the kernel tracer
367 \-u, \-\-userspace
368 Apply for the user-space tracer
369 .fi
370
371 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
372 .nf
373 Disable tracing event
374
375 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
376 NAME\fP again.
377
378 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
379 file.
380 .fi
381
382 .B OPTIONS:
383
384 .nf
385 \-h, \-\-help
386 Show summary of possible options and commands.
387 \-\-list-options
388 Simple listing of options
389 \-s, \-\-session
390 Apply on session name
391 \-k, \-\-kernel
392 Apply for the kernel tracer
393 \-u, \-\-userspace
394 Apply for the user-space tracer
395 .fi
396
397 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
398 .nf
399 List tracing session information.
400
401 With no arguments, it will list available tracing session(s).
402
403 With the session name, it will display the details of the session including
404 the trace file path, the associated channels and their state (activated
405 and deactivated), the activated events and more.
406
407 With \-k alone, it will list all available kernel events (except the system
408 calls events).
409 With \-u alone, it will list all available user-space events from registered
410 applications. Here is an example of 'lttng list \-u':
411
412 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
413 ust_tests_hello:tptest_sighandler (type: tracepoint)
414 ust_tests_hello:tptest (type: tracepoint)
415
416 You can now enable any event listed by using the name :
417 \fBust_tests_hello:tptest\fP.
418 .fi
419
420 .B OPTIONS:
421
422 .nf
423 \-h, \-\-help
424 Show summary of possible options and commands.
425 \-\-list-options
426 Simple listing of options
427 \-k, \-\-kernel
428 Select kernel domain
429 \-u, \-\-userspace
430 Select user-space domain.
431
432 Session options:
433 \-c, \-\-channel NAME
434 List details of a channel
435 \-d, \-\-domain
436 List available domain(s)
437 .fi
438
439 .IP "\fBset-session\fP NAME"
440 .nf
441 Set current session name
442
443 Will change the session name in the .lttngrc file.
444 .fi
445
446 .B OPTIONS:
447
448 .nf
449 \-h, \-\-help
450 Show summary of possible options and commands.
451 \-\-list-options
452 Simple listing of options
453 .fi
454
455 .IP
456
457 .IP "\fBstart\fP [OPTIONS] [NAME]"
458 .nf
459 Start tracing
460
461 It will start tracing for all tracers for a specific tracing session.
462
463 If NAME is omitted, the session name is taken from the .lttngrc file.
464 .fi
465
466 .B OPTIONS:
467
468 .nf
469 \-h, \-\-help
470 Show summary of possible options and commands.
471 \-\-list-options
472 Simple listing of options
473 .fi
474
475 .IP
476
477 .IP "\fBstop\fP [OPTIONS] [NAME]"
478 .nf
479 Stop tracing
480
481 It will stop tracing for all tracers for a specific tracing session.
482
483 If NAME is omitted, the session name is taken from the .lttngrc file.
484 .fi
485
486 .B OPTIONS:
487
488 .nf
489 \-h, \-\-help
490 Show summary of possible options and commands.
491 \-\-list-options
492 Simple listing of options
493 .fi
494
495 .IP
496
497 .IP "\fBversion\fP"
498 .nf
499 Show version information
500 .fi
501
502 .B OPTIONS:
503
504 .nf
505 \-h, \-\-help
506 Show summary of possible options and commands.
507 \-\-list-options
508 Simple listing of options
509 .fi
510
511 .IP
512
513 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
514 .nf
515 View traces of a tracing session
516
517 By default, the babeltrace viewer will be used for text viewing.
518
519 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
520
521 .fi
522
523 .B OPTIONS:
524
525 .nf
526 \-h, \-\-help
527 Show this help
528 \-\-list-options
529 Simple listing of options
530 \-t, \-\-trace-path PATH
531 Trace directory path for the viewer
532 \-e, \-\-viewer CMD
533 Specify viewer and/or options to use
534 This will completely override the default viewers so
535 please make sure to specify the full command. The trace
536 directory path of the session will be appended at the end
537 to the arguments
538 .fi
539
540 .SH "EXIT VALUES"
541
542 .IP "0"
543 Success
544
545 .IP "1"
546 Command error
547
548 .IP "2"
549 Undefined command
550
551 .IP "3"
552 Fatal error
553
554 .IP "4"
555 Command warning
556
557 .IP "16"
558 No session found by the name given
559
560 .IP "18"
561 Error in session creation
562
563 .IP "21"
564 Error in application(s) listing
565
566 .IP "28"
567 Session name already exists
568
569 .IP "33"
570 Kernel tracer unavailable
571
572 .IP "35"
573 Kernel event exists
574
575 .IP "37"
576 Kernel channel exists
577
578 .IP "38"
579 Kernel channel creation failed
580
581 .IP "39"
582 Kernel channel not found
583
584 .IP "40"
585 Kernel channel disable failed
586
587 .IP "41"
588 Kernel channel enable failed
589
590 .IP "42"
591 Kernel context failed
592
593 .IP "43"
594 Kernel enable event failed
595
596 .IP "44"
597 Kernel disable event failed
598
599 .IP "53"
600 Kernel listing events failed
601
602 .IP "60"
603 UST channel disable failed
604
605 .IP "61"
606 UST channel enable failed
607
608 .IP "62"
609 UST adding context failed
610
611 .IP "63"
612 UST event enable failed
613
614 .IP "64"
615 UST event disable failed
616
617 .IP "66"
618 UST start failed
619
620 .IP "67"
621 UST stop failed
622
623 .IP "75"
624 UST event exists
625
626 .IP "76"
627 UST event not found
628
629 .IP "77"
630 UST context exists
631
632 .IP "78"
633 UST invalid context
634
635 .IP "79"
636 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
637 user membership.
638
639 .IP "80"
640 Tracing already started
641
642 .IP "81"
643 Tracing already stopped
644
645 .IP "98"
646 No UST consumer detected
647
648 .IP "99"
649 No Kernel consumer detected
650
651 .IP "100"
652 Event already enabled with different loglevel
653 .PP
654 .SH "ENVIRONMENT VARIABLES"
655
656 .PP
657 Note that all command line options override environment variables.
658 .PP
659
660 .PP
661 .IP "LTTNG_SESSIOND_PATH"
662 Allows one to specify the full session daemon binary path to lttng command line
663 tool. You can also use \-\-sessiond-path option having the same effect.
664 .SH "SEE ALSO"
665
666 .PP
667 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
668 .PP
669 .SH "BUGS"
670
671 .PP
672 No show stopper bugs are known yet in this version.
673
674 If you encounter any issues or usability problem, please report it on our
675 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
676 .SH "CREDITS"
677
678 .PP
679 lttng is distributed under the GNU General Public License version 2. See the file
680 COPYING for details.
681 .PP
682 A Web site is available at http://lttng.org for more information on the LTTng
683 project.
684 .PP
685 You can also find our git tree at http://git.lttng.org.
686 .PP
687 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
688 .PP
689 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
690 .PP
691 .SH "THANKS"
692
693 .PP
694 Thanks to Yannick Brosseau without whom this project would never have been so
695 lean and mean! Also thanks to the Ericsson teams working on tracing which
696 helped us greatly with detailed bug reports and unusual test cases.
697
698 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
699 maintainer) and Jon Bernard for our Debian packages.
700
701 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
702 Montreal for the LTTng journey.
703 .PP
704 .SH "AUTHORS"
705
706 .PP
707 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
708 David Goulet. More people have since contributed to it. It is currently
709 maintained by David Goulet <dgoulet@efficios.com>.
710 .PP
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