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