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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 \-\-filter 'expression'
344 Set a filter on a newly enabled event.
345 Filter expression on event fields event recording
346 depends on evaluation. Only specify on first activation
347 of a given event within a session. Filter only allowed
348 when enabling events within a session before tracing is
349 started.
350 .fi
351
352 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
353 .nf
354 Disable tracing channel
355
356 Disabling a channel makes all event(s) in that channel to stop tracing. You can
357 enable it back by calling \fBlttng enable-channel NAME\fP again.
358
359 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
360 file.
361 .fi
362
363 .B OPTIONS:
364
365 .nf
366 \-h, \-\-help
367 Show summary of possible options and commands.
368 \-\-list-options
369 Simple listing of options
370 \-s, \-\-session
371 Apply on session name
372 \-k, \-\-kernel
373 Apply for the kernel tracer
374 \-u, \-\-userspace
375 Apply for the user-space tracer
376 .fi
377
378 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
379 .nf
380 Disable tracing event
381
382 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
383 NAME\fP again.
384
385 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
386 file.
387 .fi
388
389 .B OPTIONS:
390
391 .nf
392 \-h, \-\-help
393 Show summary of possible options and commands.
394 \-\-list-options
395 Simple listing of options
396 \-s, \-\-session
397 Apply on session name
398 \-k, \-\-kernel
399 Apply for the kernel tracer
400 \-u, \-\-userspace
401 Apply for the user-space tracer
402 .fi
403
404 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
405 .nf
406 List tracing session information.
407
408 With no arguments, it will list available tracing session(s).
409
410 With the session name, it will display the details of the session including
411 the trace file path, the associated channels and their state (activated
412 and deactivated), the activated events and more.
413
414 With \-k alone, it will list all available kernel events (except the system
415 calls events).
416 With \-u alone, it will list all available user-space events from registered
417 applications. Here is an example of 'lttng list \-u':
418
419 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
420 ust_tests_hello:tptest_sighandler (type: tracepoint)
421 ust_tests_hello:tptest (type: tracepoint)
422
423 You can now enable any event listed by using the name :
424 \fBust_tests_hello:tptest\fP.
425 .fi
426
427 .B OPTIONS:
428
429 .nf
430 \-h, \-\-help
431 Show summary of possible options and commands.
432 \-\-list-options
433 Simple listing of options
434 \-k, \-\-kernel
435 Select kernel domain
436 \-u, \-\-userspace
437 Select user-space domain.
438
439 Session options:
440 \-c, \-\-channel NAME
441 List details of a channel
442 \-d, \-\-domain
443 List available domain(s)
444 .fi
445
446 .IP "\fBset-session\fP NAME"
447 .nf
448 Set current session name
449
450 Will change the session name in the .lttngrc file.
451 .fi
452
453 .B OPTIONS:
454
455 .nf
456 \-h, \-\-help
457 Show summary of possible options and commands.
458 \-\-list-options
459 Simple listing of options
460 .fi
461
462 .IP
463
464 .IP "\fBstart\fP [OPTIONS] [NAME]"
465 .nf
466 Start tracing
467
468 It will start tracing for all tracers for a specific tracing session.
469
470 If NAME is omitted, the session name is taken from the .lttngrc file.
471 .fi
472
473 .B OPTIONS:
474
475 .nf
476 \-h, \-\-help
477 Show summary of possible options and commands.
478 \-\-list-options
479 Simple listing of options
480 .fi
481
482 .IP
483
484 .IP "\fBstop\fP [OPTIONS] [NAME]"
485 .nf
486 Stop tracing
487
488 It will stop tracing for all tracers for a specific tracing session.
489
490 If NAME is omitted, the session name is taken from the .lttngrc file.
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 "\fBversion\fP"
505 .nf
506 Show version information
507 .fi
508
509 .B OPTIONS:
510
511 .nf
512 \-h, \-\-help
513 Show summary of possible options and commands.
514 \-\-list-options
515 Simple listing of options
516 .fi
517
518 .IP
519
520 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
521 .nf
522 View traces of a tracing session
523
524 By default, the babeltrace viewer will be used for text viewing.
525
526 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
527
528 .fi
529
530 .B OPTIONS:
531
532 .nf
533 \-h, \-\-help
534 Show this help
535 \-\-list-options
536 Simple listing of options
537 \-t, \-\-trace-path PATH
538 Trace directory path for the viewer
539 \-e, \-\-viewer CMD
540 Specify viewer and/or options to use
541 This will completely override the default viewers so
542 please make sure to specify the full command. The trace
543 directory path of the session will be appended at the end
544 to the arguments
545 .fi
546
547 .SH "EXIT VALUES"
548
549 .IP "0"
550 Success
551
552 .IP "1"
553 Command error
554
555 .IP "2"
556 Undefined command
557
558 .IP "3"
559 Fatal error
560
561 .IP "4"
562 Command warning
563
564 .IP "16"
565 No session found by the name given
566
567 .IP "18"
568 Error in session creation
569
570 .IP "21"
571 Error in application(s) listing
572
573 .IP "28"
574 Session name already exists
575
576 .IP "33"
577 Kernel tracer unavailable
578
579 .IP "35"
580 Kernel event exists
581
582 .IP "37"
583 Kernel channel exists
584
585 .IP "38"
586 Kernel channel creation failed
587
588 .IP "39"
589 Kernel channel not found
590
591 .IP "40"
592 Kernel channel disable failed
593
594 .IP "41"
595 Kernel channel enable failed
596
597 .IP "42"
598 Kernel context failed
599
600 .IP "43"
601 Kernel enable event failed
602
603 .IP "44"
604 Kernel disable event failed
605
606 .IP "53"
607 Kernel listing events failed
608
609 .IP "60"
610 UST channel disable failed
611
612 .IP "61"
613 UST channel enable failed
614
615 .IP "62"
616 UST adding context failed
617
618 .IP "63"
619 UST event enable failed
620
621 .IP "64"
622 UST event disable failed
623
624 .IP "66"
625 UST start failed
626
627 .IP "67"
628 UST stop failed
629
630 .IP "75"
631 UST event exists
632
633 .IP "76"
634 UST event not found
635
636 .IP "77"
637 UST context exists
638
639 .IP "78"
640 UST invalid context
641
642 .IP "79"
643 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
644 user membership.
645
646 .IP "80"
647 Tracing already started
648
649 .IP "81"
650 Tracing already stopped
651
652 .IP "98"
653 No UST consumer detected
654
655 .IP "99"
656 No Kernel consumer detected
657
658 .IP "100"
659 Event already enabled with different loglevel
660 .PP
661 .SH "ENVIRONMENT VARIABLES"
662
663 .PP
664 Note that all command line options override environment variables.
665 .PP
666
667 .PP
668 .IP "LTTNG_SESSIOND_PATH"
669 Allows one to specify the full session daemon binary path to lttng command line
670 tool. You can also use \-\-sessiond-path option having the same effect.
671 .SH "SEE ALSO"
672
673 .PP
674 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
675 .PP
676 .SH "BUGS"
677
678 .PP
679 No show stopper bugs are known yet in this version.
680
681 If you encounter any issues or usability problem, please report it on our
682 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
683 .SH "CREDITS"
684
685 .PP
686 lttng is distributed under the GNU General Public License version 2. See the file
687 COPYING for details.
688 .PP
689 A Web site is available at http://lttng.org for more information on the LTTng
690 project.
691 .PP
692 You can also find our git tree at http://git.lttng.org.
693 .PP
694 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
695 .PP
696 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
697 .PP
698 .SH "THANKS"
699
700 .PP
701 Thanks to Yannick Brosseau without whom this project would never have been so
702 lean and mean! Also thanks to the Ericsson teams working on tracing which
703 helped us greatly with detailed bug reports and unusual test cases.
704
705 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
706 maintainer) and Jon Bernard for our Debian packages.
707
708 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
709 Montreal for the LTTng journey.
710 .PP
711 .SH "AUTHORS"
712
713 .PP
714 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
715 David Goulet. More people have since contributed to it. It is currently
716 maintained by David Goulet <dgoulet@efficios.com>.
717 .PP
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