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eba411c6 MD |
1 | .TH "LTTNG-UST" "3" "February 16, 2012" "" "" |
2 | ||
3 | .SH "NAME" | |
77ca1460 | 4 | lttng-ust \(em Linux Trace Toolkit Next Generation User-Space Tracer 2.x |
eba411c6 MD |
5 | |
6 | .SH "SYNOPSIS" | |
7 | ||
8 | .PP | |
9 | .nf | |
10 | Link liblttng-ust.so with applications, following this manpage. | |
11 | .fi | |
12 | .SH "DESCRIPTION" | |
13 | ||
14 | .PP | |
7c501923 | 15 | LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is a |
eba411c6 MD |
16 | port of the low-overhead tracing capabilities of the LTTng kernel tracer |
17 | to user-space. The library "liblttng-ust" enables tracing of | |
18 | applications and libraries. | |
19 | ||
641c659a MD |
20 | .SH "USAGE WITH TRACEF" |
21 | .PP | |
22 | The simplest way to add instrumentation to your code is by far the | |
fc0ec7f9 | 23 | tracef() API. To do it, in a nutshell: |
641c659a MD |
24 | |
25 | 1) #include <lttng/tracef.h> | |
26 | ||
27 | 2) /* in your code, use like a printf */ | |
28 | tracef("my message, this integer %d", 1234); | |
29 | ||
30 | 3) Link your program against liblttng-ust.so. | |
31 | ||
67ada458 MD |
32 | 4) Enable UST events when tracing with the following sequence of commands |
33 | from lttng-tools: | |
641c659a | 34 | |
aacb3774 | 35 | lttng create |
67ada458 | 36 | lttng enable-event -u -a |
aacb3774 | 37 | lttng start |
641c659a | 38 | [... run your program ...] |
aacb3774 MD |
39 | lttng stop |
40 | lttng view | |
641c659a MD |
41 | |
42 | That's it! | |
43 | ||
44 | If you want to have more flexibility and control on the event names, | |
45 | payload typing, etc, you can continue reading on and use the tracepoints | |
46 | below. "tracef()" is there for quick and dirty ad hoc instrumentation, | |
47 | whereas tracepoint.h is meant for thorough instrumentation of a code | |
48 | base to be integrated with an upstream project. | |
49 | .PP | |
50 | ||
51 | .SH "USAGE WITH TRACEPOINT" | |
eba411c6 MD |
52 | .PP |
53 | The simple way to generate the lttng-ust tracepoint probes is to use the | |
54 | lttng-gen-tp(1) tool. See the lttng-gen-tp(1) manpage for explanation. | |
55 | .PP | |
56 | ||
57 | .PP | |
58 | Here is the way to do it manually, without the lttng-gen-tp(1) helper | |
59 | script, through an example: | |
60 | .PP | |
61 | ||
62 | .SH "CREATION OF TRACEPOINT PROVIDER" | |
63 | ||
64 | .nf | |
65 | ||
66 | To create a tracepoint provider, within a build tree similar to | |
dfc45f18 MD |
67 | examples/easy-ust installed with lttng-ust documentation, see |
68 | sample_component_provider.h for the general layout. You will need to | |
69 | define TRACEPOINT_CREATE_PROBES before including your tracepoint | |
70 | provider probe in one source file of your application. See tp.c from | |
71 | easy-ust for an example of a tracepoint probe source file. This manpage | |
72 | will focus on the various types that can be recorded into a trace | |
73 | event: | |
eba411c6 MD |
74 | |
75 | TRACEPOINT_EVENT( | |
76 | /* | |
77 | * provider name, not a variable but a string starting with a | |
a106a9f8 | 78 | * letter and containing either letters, numbers or underscores. |
eba411c6 MD |
79 | * Needs to be the same as TRACEPOINT_PROVIDER. Needs to |
80 | * follow the namespacing guide-lines in lttng/tracepoint.h: | |
a106a9f8 JG |
81 | * |
82 | * Must be included before include tracepoint provider | |
eba411c6 MD |
83 | * ex.: project_event |
84 | * ex.: project_component_event | |
85 | * | |
86 | * Optional company name goes here | |
87 | * ex.: com_efficios_project_component_event | |
88 | * | |
89 | * In this example, "sample" is the project, and "component" is the | |
90 | * component. | |
91 | */ | |
92 | sample_component, | |
93 | ||
94 | /* | |
04fc40ad MD |
95 | * tracepoint name, characters permitted follow the same |
96 | * constraints as the provider name. The name of this example | |
97 | * event is "sample_event". | |
eba411c6 | 98 | */ |
04fc40ad | 99 | sample_event, |
eba411c6 MD |
100 | |
101 | /* | |
a106a9f8 | 102 | * TP_ARGS macro contains the arguments passed for the tracepoint |
eba411c6 MD |
103 | * it is in the following format |
104 | * TP_ARGS(type1, name1, type2, name2, ... type10, | |
105 | name10) | |
a106a9f8 JG |
106 | * where there can be from zero to ten elements. |
107 | * typeN is the datatype, such as int, struct or double **. | |
eba411c6 | 108 | * name is the variable name (in "int myInt" the name would be |
a106a9f8 | 109 | * myint) |
eba411c6 MD |
110 | * TP_ARGS() is valid to mean no arguments |
111 | * TP_ARGS(void) is valid too | |
112 | */ | |
113 | TP_ARGS(int, anint, int, netint, long *, values, | |
114 | char *, text, size_t, textlen, | |
115 | double, doublearg, float, floatarg), | |
116 | ||
117 | /* | |
a106a9f8 | 118 | * TP_FIELDS describes how to write the fields of the trace event. |
eba411c6 MD |
119 | * You can put expressions in the "argument expression" area, |
120 | * typically using the input arguments from TP_ARGS. | |
121 | */ | |
122 | TP_FIELDS( | |
123 | /* | |
124 | * ctf_integer: standard integer field. | |
125 | * args: (type, field name, argument expression) | |
126 | */ | |
127 | ctf_integer(int, intfield, anint) | |
128 | ctf_integer(long, longfield, anint) | |
129 | ||
130 | /* | |
131 | * ctf_integer_hex: integer field printed as hexadecimal. | |
132 | * args: (type, field name, argument expression) | |
133 | */ | |
134 | ctf_integer_hex(int, intfield2, anint) | |
135 | ||
136 | /* | |
137 | * ctf_integer_network: integer field in network byte | |
138 | * order. (_hex: printed as hexadecimal too) | |
139 | * args: (type, field name, argument expression) | |
140 | */ | |
141 | ctf_integer_network(int, netintfield, netint) | |
142 | ctf_integer_network_hex(int, netintfieldhex, netint) | |
143 | ||
144 | /* | |
145 | * ctf_array: a statically-sized array. | |
146 | * args: (type, field name, argument expression, value) | |
a106a9f8 | 147 | */ |
eba411c6 MD |
148 | ctf_array(long, arrfield1, values, 3) |
149 | ||
150 | /* | |
151 | * ctf_array_text: a statically-sized array, printed as | |
152 | * a string. No need to be terminated by a null | |
153 | * character. | |
2f65f1f5 | 154 | * Behavior is undefined if "text" argument is NULL. |
a106a9f8 | 155 | */ |
eba411c6 MD |
156 | ctf_array_text(char, arrfield2, text, 10) |
157 | ||
158 | /* | |
159 | * ctf_sequence: a dynamically-sized array. | |
160 | * args: (type, field name, argument expression, | |
161 | * type of length expression, length expression) | |
efbad5cc MD |
162 | * The "type of length expression" needs to be an |
163 | * unsigned type. As a reminder, "unsigned char" should | |
164 | * be preferred to "char", since the signedness of | |
165 | * "char" is implementation-defined. | |
2f65f1f5 | 166 | * Behavior is undefined if "text" argument is NULL. |
a106a9f8 | 167 | */ |
eba411c6 MD |
168 | ctf_sequence(char, seqfield1, text, |
169 | size_t, textlen) | |
170 | ||
171 | /* | |
172 | * ctf_sequence_text: a dynamically-sized array, printed | |
173 | * as string. No need to be null-terminated. | |
2f65f1f5 | 174 | * Behavior is undefined if "text" argument is NULL. |
eba411c6 MD |
175 | */ |
176 | ctf_sequence_text(char, seqfield2, text, | |
177 | size_t, textlen) | |
178 | ||
179 | /* | |
180 | * ctf_string: null-terminated string. | |
181 | * args: (field name, argument expression) | |
2f65f1f5 | 182 | * Behavior is undefined if "text" argument is NULL. |
eba411c6 MD |
183 | */ |
184 | ctf_string(stringfield, text) | |
185 | ||
186 | /* | |
187 | * ctf_float: floating-point number. | |
188 | * args: (type, field name, argument expression) | |
189 | */ | |
190 | ctf_float(float, floatfield, floatarg) | |
191 | ctf_float(double, doublefield, doublearg) | |
192 | ) | |
193 | ) | |
7d381d6e MD |
194 | |
195 | There can be an arbitrary number of tracepoint providers within an | |
196 | application, but they must each have their own provider name. Duplicate | |
197 | provider names are not allowed. | |
198 | ||
eba411c6 MD |
199 | .fi |
200 | ||
5883c06f MD |
201 | .SH "ASSIGNING LOGLEVEL TO EVENTS" |
202 | ||
203 | .nf | |
204 | ||
205 | Optionally, a loglevel can be assigned to a TRACEPOINT_EVENT using the | |
206 | following construct: | |
207 | ||
208 | TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >, | |
209 | < event >, < loglevel_name >) | |
210 | ||
7c501923 | 211 | The first field is the provider name, the second field is the name of |
5883c06f MD |
212 | the tracepoint, and the third field is the loglevel name. A |
213 | TRACEPOINT_EVENT should be declared prior to the the TRACEPOINT_LOGLEVEL | |
214 | for a given tracepoint name. The TRACEPOINT_PROVIDER must be already | |
215 | declared before declaring a TRACEPOINT_LOGLEVEL. | |
216 | ||
217 | The loglevels go from 0 to 14. Higher numbers imply the most verbosity | |
218 | (higher event throughput expected. | |
a106a9f8 | 219 | |
5883c06f MD |
220 | Loglevels 0 through 6, and loglevel 14, match syslog(3) loglevels |
221 | semantic. Loglevels 7 through 13 offer more fine-grained selection of | |
222 | debug information. | |
a106a9f8 | 223 | |
5883c06f MD |
224 | TRACE_EMERG 0 |
225 | system is unusable | |
a106a9f8 | 226 | |
5883c06f MD |
227 | TRACE_ALERT 1 |
228 | action must be taken immediately | |
a106a9f8 | 229 | |
5883c06f MD |
230 | TRACE_CRIT 2 |
231 | critical conditions | |
a106a9f8 | 232 | |
5883c06f MD |
233 | TRACE_ERR 3 |
234 | error conditions | |
a106a9f8 | 235 | |
5883c06f MD |
236 | TRACE_WARNING 4 |
237 | warning conditions | |
a106a9f8 | 238 | |
5883c06f MD |
239 | TRACE_NOTICE 5 |
240 | normal, but significant, condition | |
a106a9f8 | 241 | |
5883c06f MD |
242 | TRACE_INFO 6 |
243 | informational message | |
a106a9f8 | 244 | |
5883c06f MD |
245 | TRACE_DEBUG_SYSTEM 7 |
246 | debug information with system-level scope (set of programs) | |
a106a9f8 | 247 | |
5883c06f MD |
248 | TRACE_DEBUG_PROGRAM 8 |
249 | debug information with program-level scope (set of processes) | |
a106a9f8 | 250 | |
5883c06f MD |
251 | TRACE_DEBUG_PROCESS 9 |
252 | debug information with process-level scope (set of modules) | |
a106a9f8 | 253 | |
5883c06f MD |
254 | TRACE_DEBUG_MODULE 10 |
255 | debug information with module (executable/library) scope (set of | |
256 | units) | |
a106a9f8 | 257 | |
5883c06f MD |
258 | TRACE_DEBUG_UNIT 11 |
259 | debug information with compilation unit scope (set of functions) | |
a106a9f8 | 260 | |
5883c06f MD |
261 | TRACE_DEBUG_FUNCTION 12 |
262 | debug information with function-level scope | |
a106a9f8 | 263 | |
5883c06f MD |
264 | TRACE_DEBUG_LINE 13 |
265 | debug information with line-level scope (TRACEPOINT_EVENT default) | |
a106a9f8 | 266 | |
5883c06f | 267 | TRACE_DEBUG 14 |
1e3b0059 | 268 | debug-level message |
5883c06f MD |
269 | |
270 | See lttng(1) for information on how to use LTTng-UST loglevels. | |
271 | ||
272 | .fi | |
273 | ||
eba411c6 MD |
274 | .SH "ADDING TRACEPOINTS TO YOUR CODE" |
275 | ||
276 | .nf | |
277 | ||
278 | Include the provider header in each C files you plan to instrument, | |
279 | following the building/linking directives in the next section. | |
280 | ||
281 | For instance, add within a function: | |
282 | ||
283 | tracepoint(ust_tests_hello, tptest, i, netint, values, | |
284 | text, strlen(text), dbl, flt); | |
285 | ||
286 | As a call to the tracepoint. It will only be activated when requested by | |
287 | lttng(1) through lttng-sessiond(8). | |
288 | ||
d646ca64 MD |
289 | Even though LTTng-UST supports tracepoint() call site duplicates having |
290 | the same provider and event name, it is recommended to use a | |
291 | provider event name pair only once within the source code to help | |
7c501923 | 292 | map events back to their call sites when analyzing the trace. |
eba411c6 MD |
293 | .fi |
294 | ||
295 | .SH "BUILDING/LINKING THE TRACEPOINT PROVIDER" | |
296 | ||
297 | .nf | |
298 | There are 2 ways to compile the Tracepoint Provider with the | |
299 | application: either statically or dynamically. Please follow | |
300 | carefully: | |
301 | ||
302 | 1.1) Compile the Tracepoint provider with the application, either | |
303 | directly or through a static library (.a): | |
304 | - Into exactly one object of your application: define | |
305 | "TRACEPOINT_DEFINE" and include the tracepoint provider. | |
9b6435af | 306 | - Use "\-I." for the compilation unit containing the tracepoint |
eba411c6 | 307 | provider include (e.g. tp.c). |
9b6435af | 308 | - Link application with "\-ldl". |
eba411c6 | 309 | - If building the provider directly into the application, |
9b6435af | 310 | link the application with "\-llttng-ust". |
eba411c6 | 311 | - If building a static library for the provider, link the static |
38f5f440 | 312 | library with "\-llttng-ust". |
eba411c6 MD |
313 | - Include the tracepoint provider header into all C files using |
314 | the provider. | |
a106a9f8 JG |
315 | - Examples: |
316 | - doc/examples/easy-ust/ sample.c sample_component_provider.h tp.c | |
317 | Makefile | |
318 | - doc/examples/hello-static-lib/ hello.c tp.c ust_test_hello.h Makefile | |
eba411c6 MD |
319 | |
320 | 2) Compile the Tracepoint Provider separately from the application, | |
321 | using dynamic linking: | |
322 | - Into exactly one object of your application: define | |
323 | "TRACEPOINT_DEFINE" _and_ also define | |
324 | "TRACEPOINT_PROBE_DYNAMIC_LINKAGE", then include the tracepoint | |
325 | provider header. | |
326 | - Include the tracepoint provider header into all instrumented C | |
327 | files that use the provider. | |
9b6435af AM |
328 | - Compile the tracepoint provider with "\-I.". |
329 | - Link the tracepoint provider with "\-llttng-ust". | |
330 | - Link application with "\-ldl". | |
eba411c6 MD |
331 | - Set a LD_PRELOAD environment to preload the tracepoint provider |
332 | shared object before starting the application when tracing is | |
13fb2d2c JG |
333 | needed. Another way is to dlopen the tracepoint probe when needed |
334 | by the application. | |
eba411c6 | 335 | - Example: |
a106a9f8 | 336 | - doc/examples/demo demo.c tp*.c ust_tests_demo*.h demo-trace Makefile |
eba411c6 | 337 | |
13fb2d2c JG |
338 | - Note about dlclose() usage: it is not safe to use dlclose on a |
339 | provider shared object that is being actively used for tracing due | |
340 | to a lack of reference counting from lttng-ust to the used shared | |
341 | object. | |
eba411c6 MD |
342 | - Enable instrumentation and control tracing with the "lttng" command |
343 | from lttng-tools. See lttng-tools doc/quickstart.txt. | |
2bda849d MD |
344 | - Note for C++ support: although an application instrumented with |
345 | tracepoints can be compiled with g++, tracepoint probes should be | |
346 | compiled with gcc (only tested with gcc so far). | |
eba411c6 MD |
347 | |
348 | .fi | |
349 | ||
0a7c55a5 MD |
350 | .SH "USING LTTNG UST WITH DAEMONS" |
351 | ||
352 | .nf | |
353 | Some extra care is needed when using liblttng-ust with daemon | |
354 | applications that call fork(), clone(), or BSD rfork() without a | |
355 | following exec() family system call. The library "liblttng-ust-fork.so" | |
356 | needs to be preloaded for the application (launch with e.g. | |
357 | LD_PRELOAD=liblttng-ust-fork.so appname). | |
358 | ||
359 | .fi | |
360 | ||
94c9c48d MD |
361 | .SH "CONTEXT" |
362 | ||
363 | .PP | |
364 | Context information can be prepended by the tracer before each, or some, | |
365 | events. The following context information is supported by LTTng-UST: | |
366 | .PP | |
367 | ||
368 | .PP | |
369 | .IP "vtid" | |
370 | Virtual thread ID: thread ID as seen from the point of view of the | |
371 | process namespace. | |
372 | .PP | |
373 | ||
374 | .PP | |
375 | .IP "vpid" | |
376 | Virtual process ID: process ID as seen from the point of view of the | |
377 | process namespace. | |
378 | .PP | |
379 | ||
f6df8626 PW |
380 | .PP |
381 | .IP "ip" | |
382 | Instruction pointer: Enables recording of the exact location where a tracepoint | |
383 | was emitted. Can be used to reverse-lookup the source location that caused the | |
384 | event to be emitted. | |
385 | .PP | |
386 | ||
94c9c48d MD |
387 | .PP |
388 | .IP "procname" | |
389 | Thread name, as set by exec() or prctl(). It is recommended that | |
390 | programs set their thread name with prctl() before hitting the first | |
391 | tracepoint for that thread. | |
392 | .PP | |
393 | ||
394 | .PP | |
395 | .IP "pthread_id" | |
396 | Pthread identifier. Can be used on architectures where pthread_t maps | |
397 | nicely to an unsigned long type. | |
398 | .PP | |
399 | ||
ce46717a | 400 | .SH "BASE ADDRESS STATEDUMP" |
f6df8626 PW |
401 | |
402 | .PP | |
403 | If an application that uses liblttng-ust.so becomes part of a session, | |
404 | information about its currently loaded shared objects will be traced to the | |
405 | session at session-enable time. To record this information, the following event | |
406 | needs to be enabled: | |
407 | .PP | |
408 | .IP "ust_baddr_statedump:soinfo" | |
409 | This event is used to trace a currently loaded shared object. The base address | |
410 | (where the dynamic linker has placed the shared object) is recorded in the | |
6d262185 MD |
411 | "baddr" field. The path to the shared object gets recorded in the |
412 | "sopath" field (as string). The file size of the loaded object (in | |
413 | bytes) is recorded to the "size" field and its time of last modification | |
414 | (in seconds since Epoch) is recorded in the "mtime" field. | |
f6df8626 | 415 | .PP |
6d262185 MD |
416 | If the event above is enabled, a series of "ust_baddr_statedump:soinfo" |
417 | events is recorded at session-enable time. It represents the state of | |
418 | currently loaded shared objects for the traced process. If this | |
419 | information gets combined with the lttng-ust-dl(3) instrumentation, all | |
420 | aspects of dynamic loading that are relevant for symbol and | |
421 | line number lookup are traced by LTTng. | |
f6df8626 | 422 | .PP |
eba411c6 MD |
423 | .SH "ENVIRONMENT VARIABLES" |
424 | ||
425 | .PP | |
426 | .IP "LTTNG_UST_DEBUG" | |
427 | Activate liblttng-ust debug output. | |
428 | .PP | |
429 | .IP "LTTNG_UST_REGISTER_TIMEOUT" | |
430 | The environment variable "LTTNG_UST_REGISTER_TIMEOUT" can be used to | |
431 | specify how long the applications should wait for sessiond | |
432 | "registration done" command before proceeding to execute the main | |
433 | program. The default is 3000ms (3 seconds). The timeout value is | |
434 | specified in milliseconds. The value 0 means "don't wait". The value | |
9b6435af | 435 | \-1 means "wait forever". Setting this environment variable to 0 is |
eba411c6 MD |
436 | recommended for applications with time constraints on the process |
437 | startup time. | |
438 | .PP | |
ce46717a PW |
439 | .IP "LTTNG_UST_WITHOUT_BADDR_STATEDUMP" |
440 | Prevent liblttng-ust to perform a base-address statedump on session-enable. | |
f6df8626 | 441 | .PP |
eba411c6 MD |
442 | |
443 | .SH "SEE ALSO" | |
444 | ||
445 | .PP | |
d1eaa4d7 | 446 | lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-ust-cyg-profile(3), |
f6df8626 | 447 | lttng-ust-dl(3), lttng-sessiond(8) |
eba411c6 | 448 | .PP |
ff42aeef MD |
449 | |
450 | .SH "COMPATIBILITY" | |
451 | ||
452 | .PP | |
453 | Older lttng-ust libraries reject more recent, and incompatible, probe | |
cf949d07 | 454 | providers. Newer lttng-ust libraries accept older probe providers, even |
ff42aeef MD |
455 | though some newer features might not be available with those providers. |
456 | .PP | |
457 | ||
eba411c6 MD |
458 | .SH "BUGS" |
459 | ||
460 | .PP | |
ff42aeef MD |
461 | LTTng-UST 2.0 and 2.1 lttng-ust libraries do not check for probe |
462 | provider version compatibility. This can lead to out-of-bound accesses | |
463 | when using a more recent probe provider with an older lttng-ust library. | |
464 | These error only trigger when tracing is active. This issue has been | |
465 | fixed in LTTng-UST 2.2. | |
eba411c6 MD |
466 | |
467 | If you encounter any issues or usability problem, please report it on | |
468 | our mailing list <lttng-dev@lists.lttng.org> to help improve this | |
469 | project. | |
470 | .SH "CREDITS" | |
471 | ||
472 | liblttng-ust is distributed under the GNU Lesser General Public License | |
473 | version 2.1. The headers are distributed under the MIT license. | |
474 | .PP | |
475 | See http://lttng.org for more information on the LTTng project. | |
476 | .PP | |
477 | Mailing list for support and development: <lttng-dev@lists.lttng.org>. | |
478 | .PP | |
479 | You can find us on IRC server irc.oftc.net (OFTC) in #lttng. | |
480 | .PP | |
481 | .SH "THANKS" | |
482 | ||
483 | Thanks to Ericsson for funding this work, providing real-life use-cases, | |
484 | and testing. | |
485 | ||
486 | Special thanks to Michel Dagenais and the DORSAL laboratory at | |
487 | Polytechnique de Montreal for the LTTng journey. | |
488 | .PP | |
489 | .SH "AUTHORS" | |
490 | ||
491 | .PP | |
492 | liblttng-ust was originally written by Mathieu Desnoyers, with additional | |
493 | contributions from various other people. It is currently maintained by | |
494 | Mathieu Desnoyers <mathieu.desnoyers@efficios.com>. | |
495 | .PP |