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4ddbd0b7 PP |
1 | lttng-ust(3) |
2 | ============ | |
3 | :object-type: library | |
4 | ||
5 | ||
6 | NAME | |
7 | ---- | |
8 | lttng-ust - LTTng user space tracing | |
9 | ||
10 | ||
11 | SYNOPSIS | |
12 | -------- | |
13 | [verse] | |
14 | *#include <lttng/tracepoint.h>* | |
15 | ||
16 | [verse] | |
17 | #define *TRACEPOINT_ENUM*('prov_name', 'enum_name', 'mappings') | |
18 | #define *TRACEPOINT_EVENT*('prov_name', 't_name', 'args', 'fields') | |
a347dab0 PP |
19 | #define *TRACEPOINT_EVENT_CLASS*('prov_name', 'class_name', 'args', 'fields') |
20 | #define *TRACEPOINT_EVENT_INSTANCE*('prov_name', 'class_name', 't_name', 'args') | |
4ddbd0b7 PP |
21 | #define *TRACEPOINT_LOGLEVEL*('prov_name', 't_name', 'level') |
22 | #define *ctf_array*('int_type', 'field_name', 'expr', 'count') | |
23 | #define *ctf_array_nowrite*('int_type', 'field_name', 'expr', 'count') | |
2842c6c8 PP |
24 | #define *ctf_array_hex*('int_type', 'field_name', 'expr', 'count') |
25 | #define *ctf_array_nowrite_hex*('int_type', 'field_name', 'expr', 'count') | |
26 | #define *ctf_array_network*('int_type', 'field_name', 'expr', 'count') | |
27 | #define *ctf_array_network_nowrite*('int_type', 'field_name', 'expr', 'count') | |
28 | #define *ctf_array_network_hex*('int_type', 'field_name', 'expr', 'count') | |
29 | #define *ctf_array_network_nowrite_hex*('int_type', 'field_name', 'expr', 'count') | |
4ddbd0b7 PP |
30 | #define *ctf_array_text*(char, 'field_name', 'expr', 'count') |
31 | #define *ctf_array_text_nowrite*(char, 'field_name', 'expr', 'count') | |
32 | #define *ctf_enum*('prov_name', 'enum_name', 'int_type', 'field_name', 'expr') | |
a347dab0 PP |
33 | #define *ctf_enum_nowrite*('prov_name', 'enum_name', 'int_type', 'field_name', |
34 | 'expr') | |
4ddbd0b7 PP |
35 | #define *ctf_enum_value*('label', 'value') |
36 | #define *ctf_enum_range*('label', 'start', 'end') | |
37 | #define *ctf_float*('float_type', 'field_name', 'expr') | |
38 | #define *ctf_float_nowrite*('float_type', 'field_name', 'expr') | |
39 | #define *ctf_integer*('int_type', 'field_name', 'expr') | |
40 | #define *ctf_integer_hex*('int_type', 'field_name', 'expr') | |
41 | #define *ctf_integer_network*('int_type', 'field_name', 'expr') | |
42 | #define *ctf_integer_network_hex*('int_type', 'field_name', 'expr') | |
43 | #define *ctf_integer_nowrite*('int_type', 'field_name', 'expr') | |
44 | #define *ctf_sequence*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
2842c6c8 PP |
45 | #define *ctf_sequence_nowrite*('int_type', 'field_name', 'expr', 'len_type', |
46 | 'len_expr') | |
47 | #define *ctf_sequence_hex*('int_type', 'field_name', 'expr', 'len_type', | |
48 | 'len_expr') | |
49 | #define *ctf_sequence_nowrite_hex*('int_type', 'field_name', 'expr', 'len_type', | |
50 | 'len_expr') | |
51 | #define *ctf_sequence_network*('int_type', 'field_name', 'expr', 'len_type', | |
52 | 'len_expr') | |
53 | #define *ctf_sequence_network_nowrite*('int_type', 'field_name', 'expr', | |
54 | 'len_type', 'len_expr') | |
55 | #define *ctf_sequence_network_hex*('int_type', 'field_name', 'expr', 'len_type', | |
56 | 'len_expr') | |
57 | #define *ctf_sequence_network_nowrite_hex*('int_type', 'field_name', 'expr', | |
58 | 'len_type', 'len_expr') | |
4ddbd0b7 | 59 | #define *ctf_sequence_text*(char, 'field_name', 'expr', 'len_type', 'len_expr') |
a347dab0 PP |
60 | #define *ctf_sequence_text_nowrite*(char, 'field_name', 'expr', 'len_type', |
61 | 'len_expr') | |
4ddbd0b7 PP |
62 | #define *ctf_string*('field_name', 'expr') |
63 | #define *ctf_string_nowrite*('field_name', 'expr') | |
64 | #define *do_tracepoint*('prov_name', 't_name', ...) | |
65 | #define *tracepoint*('prov_name', 't_name', ...) | |
66 | #define *tracepoint_enabled*('prov_name', 't_name') | |
67 | ||
68 | Link with `-llttng-ust -ldl`, following this man page. | |
69 | ||
70 | ||
71 | DESCRIPTION | |
72 | ----------- | |
73 | The http://lttng.org/[_Linux Trace Toolkit: next generation_] is an open | |
74 | source software package used for correlated tracing of the Linux kernel, | |
75 | user applications, and user libraries. | |
76 | ||
77 | LTTng-UST is the user space tracing component of the LTTng project. It | |
78 | is a port to user space of the low-overhead tracing capabilities of the | |
79 | LTTng Linux kernel tracer. The `liblttng-ust` library is used to trace | |
80 | user applications and libraries. | |
81 | ||
82 | NOTE: This man page is about the `liblttng-ust` library. The LTTng-UST | |
83 | project also provides Java and Python packages to trace applications | |
84 | written in those languages. How to instrument and trace Java and Python | |
85 | applications is documented in | |
86 | http://lttng.org/docs/[the online LTTng documentation]. | |
87 | ||
88 | There are three ways to use `liblttng-ust`: | |
89 | ||
90 | * Using the man:tracef(3) API, which is similar to man:printf(3). | |
91 | * Using the man:tracelog(3) API, which is man:tracef(3) with | |
92 | a log level parameter. | |
93 | * Defining your own tracepoints. See the | |
94 | <<creating-tp,Creating a tracepoint provider>> section below. | |
95 | ||
96 | ||
97 | [[creating-tp]] | |
98 | Creating a tracepoint provider | |
99 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
100 | Creating a tracepoint provider is the first step of using | |
101 | `liblttng-ust`. The next steps are: | |
102 | ||
103 | * <<tracepoint,Instrumenting your application with `tracepoint()` calls>> | |
104 | * Building your application with LTTng-UST support, either | |
105 | <<build-static,statically>> or <<build-dynamic,dynamically>>. | |
106 | ||
107 | A *tracepoint provider* is a compiled object containing the event | |
108 | probes corresponding to your custom tracepoint definitions. A tracepoint | |
109 | provider contains the code to get the size of an event and to serialize | |
110 | it, amongst other things. | |
111 | ||
112 | To create a tracepoint provider, start with the following | |
113 | _tracepoint provider header_ template: | |
114 | ||
115 | ------------------------------------------------------------------------ | |
116 | #undef TRACEPOINT_PROVIDER | |
117 | #define TRACEPOINT_PROVIDER my_provider | |
118 | ||
119 | #undef TRACEPOINT_INCLUDE | |
120 | #define TRACEPOINT_INCLUDE "./tp.h" | |
121 | ||
122 | #if !defined(_TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ) | |
123 | #define _TP_H | |
124 | ||
125 | #include <lttng/tracepoint.h> | |
126 | ||
127 | /* | |
128 | * TRACEPOINT_EVENT(), TRACEPOINT_EVENT_CLASS(), | |
129 | * TRACEPOINT_EVENT_INSTANCE(), TRACEPOINT_LOGLEVEL(), | |
130 | * and `TRACEPOINT_ENUM()` are used here. | |
131 | */ | |
132 | ||
133 | #endif /* _TP_H */ | |
134 | ||
135 | #include <lttng/tracepoint-event.h> | |
136 | ------------------------------------------------------------------------ | |
137 | ||
138 | In this template, the tracepoint provider is named `my_provider` | |
139 | (`TRACEPOINT_PROVIDER` definition). The file needs to bear the | |
140 | name of the `TRACEPOINT_INCLUDE` definition (`tp.h` in this case). | |
141 | Between `#include <lttng/tracepoint.h>` and `#endif` go | |
142 | the invocations of the <<tracepoint-event,`TRACEPOINT_EVENT()`>>, | |
143 | <<tracepoint-event-class,`TRACEPOINT_EVENT_CLASS()`>>, | |
144 | <<tracepoint-event-class,`TRACEPOINT_EVENT_INSTANCE()`>>, | |
145 | <<tracepoint-loglevel,`TRACEPOINT_LOGLEVEL()`>>, and | |
146 | <<tracepoint-enum,`TRACEPOINT_ENUM()`>> macros. | |
147 | ||
148 | NOTE: You can avoid writing the prologue and epilogue boilerplate in the | |
149 | template file above by using the man:lttng-gen-tp(1) tool shipped with | |
150 | LTTng-UST. | |
151 | ||
152 | The tracepoint provider header file needs to be included in a source | |
153 | file which looks like this: | |
154 | ||
155 | ------------------------------------------------------------------------ | |
156 | #define TRACEPOINT_CREATE_PROBES | |
157 | ||
158 | #include "tp.h" | |
159 | ------------------------------------------------------------------------ | |
160 | ||
161 | Together, those two files (let's call them `tp.h` and `tp.c`) form the | |
162 | tracepoint provider sources, ready to be compiled. | |
163 | ||
164 | You can create multiple tracepoint providers to be used in a single | |
165 | application, but each one must have its own header file. | |
166 | ||
167 | The <<tracepoint-event,`TRACEPOINT_EVENT()` usage>> section below | |
168 | shows how to use the `TRACEPOINT_EVENT()` macro to define the actual | |
169 | tracepoints in the tracepoint provider header file. | |
170 | ||
171 | See the <<example,EXAMPLE>> section below for a complete example. | |
172 | ||
173 | ||
174 | [[tracepoint-event]] | |
175 | `TRACEPOINT_EVENT()` usage | |
176 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
177 | The `TRACEPOINT_EVENT()` macro is used in a template provider | |
178 | header file (see the <<creating-tp,Creating a tracepoint provider>> | |
179 | section above) to define LTTng-UST tracepoints. | |
180 | ||
181 | The `TRACEPOINT_EVENT()` usage template is as follows: | |
182 | ||
183 | ------------------------------------------------------------------------ | |
184 | TRACEPOINT_EVENT( | |
185 | /* Tracepoint provider name */ | |
186 | my_provider, | |
187 | ||
188 | /* Tracepoint/event name */ | |
189 | my_tracepoint, | |
190 | ||
191 | /* List of tracepoint arguments (input) */ | |
192 | TP_ARGS( | |
193 | ... | |
194 | ), | |
195 | ||
196 | /* List of fields of eventual event (output) */ | |
197 | TP_FIELDS( | |
198 | ... | |
199 | ) | |
200 | ) | |
201 | ------------------------------------------------------------------------ | |
202 | ||
203 | The `TP_ARGS()` macro contains the input arguments of the tracepoint. | |
204 | Those arguments can be used in the argument expressions of the output | |
205 | fields defined in `TP_FIELDS()`. | |
206 | ||
207 | The format of the `TP_ARGS()` parameters is: C type, then argument name; | |
208 | repeat as needed, up to ten times. For example: | |
209 | ||
210 | ------------------------------------------------------------------------ | |
211 | TP_ARGS( | |
212 | int, my_int, | |
213 | const char *, my_string, | |
214 | FILE *, my_file, | |
215 | double, my_float, | |
216 | struct my_data *, my_data | |
217 | ) | |
218 | ------------------------------------------------------------------------ | |
219 | ||
220 | The `TP_FIELDS()` macro contains the output fields of the tracepoint, | |
221 | that is, the actual data that can be recorded in the payload of an | |
222 | event emitted by this tracepoint. | |
223 | ||
224 | The `TP_FIELDS()` macro contains a list of `ctf_*()` macros | |
225 | :not: separated by commas. The available macros are documented in the | |
226 | <<ctf-macros,Available `ctf_*()` field type macros>> section below. | |
227 | ||
228 | ||
229 | [[ctf-macros]] | |
230 | Available `ctf_*()` field type macros | |
231 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
232 | This section documents the available `ctf_*()` macros that can be | |
233 | inserted in the `TP_FIELDS()` macro of the | |
234 | <<tracepoint-event,`TRACEPOINT_EVENT()` macro>>. | |
235 | ||
236 | Standard integer, displayed in base 10: | |
237 | ||
238 | [verse] | |
239 | *ctf_integer*('int_type', 'field_name', 'expr') | |
240 | *ctf_integer_nowrite*('int_type', 'field_name', 'expr') | |
241 | ||
242 | Standard integer, displayed in base 16: | |
243 | ||
244 | [verse] | |
245 | *ctf_integer_hex*('int_type', 'field_name', 'expr') | |
246 | ||
247 | Integer in network byte order (big endian), displayed in base 10: | |
248 | ||
249 | [verse] | |
250 | *ctf_integer_network*('int_type', 'field_name', 'expr') | |
251 | ||
252 | Integer in network byte order, displayed in base 16: | |
253 | ||
254 | [verse] | |
255 | *ctf_integer_network_hex*('int_type', 'field_name', 'expr') | |
256 | ||
257 | Floating point number: | |
258 | ||
259 | [verse] | |
260 | *ctf_float*('float_type', 'field_name', 'expr') | |
261 | *ctf_float_nowrite*('float_type', 'field_name', 'expr') | |
262 | ||
263 | Null-terminated string: | |
264 | ||
265 | [verse] | |
266 | *ctf_string*('field_name', 'expr') | |
267 | *ctf_string_nowrite*('field_name', 'expr') | |
268 | ||
2842c6c8 PP |
269 | Statically-sized array of integers (`_hex` versions displayed in |
270 | hexadecimal, `_network` versions in network byte order): | |
4ddbd0b7 PP |
271 | |
272 | [verse] | |
273 | *ctf_array*('int_type', 'field_name', 'expr', 'count') | |
274 | *ctf_array_nowrite*('int_type', 'field_name', 'expr', 'count') | |
2842c6c8 PP |
275 | *ctf_array_hex*('int_type', 'field_name', 'expr', 'count') |
276 | *ctf_array_nowrite_hex*('int_type', 'field_name', 'expr', 'count') | |
277 | *ctf_array_network*('int_type', 'field_name', 'expr', 'count') | |
278 | *ctf_array_network_nowrite*('int_type', 'field_name', 'expr', 'count') | |
279 | *ctf_array_network_hex*('int_type', 'field_name', 'expr', 'count') | |
280 | *ctf_array_network_nowrite_hex*('int_type', 'field_name', 'expr', 'count') | |
4ddbd0b7 PP |
281 | |
282 | Statically-sized array, printed as text; no need to be null-terminated: | |
283 | ||
284 | [verse] | |
285 | *ctf_array_text*(char, 'field_name', 'expr', 'count') | |
286 | *ctf_array_text_nowrite*(char, 'field_name', 'expr', 'count') | |
287 | ||
2842c6c8 PP |
288 | Dynamically-sized array of integers (`_hex` versions displayed in |
289 | hexadecimal, `_network` versions in network byte order): | |
4ddbd0b7 PP |
290 | |
291 | [verse] | |
292 | *ctf_sequence*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
293 | *ctf_sequence_nowrite*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
2842c6c8 PP |
294 | *ctf_sequence_hex*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') |
295 | *ctf_sequence_nowrite_hex*('int_type', 'field_name', 'expr', 'len_type', | |
296 | 'len_expr') | |
297 | *ctf_sequence_network*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
298 | *ctf_sequence_network_nowrite*('int_type', 'field_name', 'expr', 'len_type', | |
299 | 'len_expr') | |
300 | *ctf_sequence_network_hex*('int_type', 'field_name', 'expr', 'len_type', | |
301 | 'len_expr') | |
a347dab0 PP |
302 | *ctf_sequence_network_nowrite_hex*('int_type', 'field_name', 'expr', |
303 | 'len_type', 'len_expr') | |
4ddbd0b7 PP |
304 | |
305 | Dynamically-sized array, displayed as text; no need to be null-terminated: | |
306 | ||
307 | [verse] | |
308 | *ctf_sequence_text*(char, 'field_name', 'expr', 'len_type', 'len_expr') | |
309 | *ctf_sequence_text_nowrite*(char, 'field_name', 'expr', 'len_type', 'len_expr') | |
310 | ||
311 | Enumeration. The enumeration field must be defined before using this | |
312 | macro with the `TRACEPOINT_ENUM()` macro. See the | |
313 | <<tracepoint-enum,`TRACEPOINT_ENUM()` usage>> section for more | |
314 | information. | |
315 | ||
316 | [verse] | |
317 | *ctf_enum*('prov_name', 'enum_name', 'int_type', 'field_name', 'expr') | |
318 | *ctf_enum_nowrite*('prov_name', 'enum_name', 'int_type', 'field_name', 'expr') | |
319 | ||
320 | The parameters are: | |
321 | ||
322 | 'int_type':: | |
323 | Integer C type. The size of this type determines the size of the | |
324 | integer/enumeration field. | |
325 | ||
326 | 'float_type':: | |
327 | Float C type (`float` or `double`). The size of this type determines | |
328 | the size of the floating point number field. | |
329 | ||
330 | 'field_name':: | |
331 | Event field name (C identifier syntax, :not: a literal string). | |
332 | ||
333 | 'expr':: | |
334 | C expression resulting in the field's value. This expression can | |
335 | use one or more arguments passed to the tracepoint. The arguments | |
336 | of a given tracepoint are defined in the `TP_ARGS()` macro (see | |
337 | the <<creating-tp,Creating a tracepoint provider>> section above). | |
338 | ||
339 | 'count':: | |
340 | Number of elements in array/sequence. This must be known at | |
341 | compile time. | |
342 | ||
343 | 'len_type':: | |
344 | Unsigned integer C type of sequence's length. | |
345 | ||
346 | 'len_expr':: | |
347 | C expression resulting in the sequence's length. This expression | |
348 | can use one or more arguments passed to the tracepoint. | |
349 | ||
350 | 'prov_name':: | |
351 | Tracepoint provider name. This must be the same as the tracepoint | |
352 | provider name used in a previous field definition. | |
353 | ||
354 | 'enum_name':: | |
355 | Name of an enumeration field previously defined with the | |
356 | `TRACEPOINT_ENUM()` macro. See the | |
357 | <<tracepoint-enum,`TRACEPOINT_ENUM()` usage>> section for more | |
358 | information. | |
359 | ||
360 | The `_nowrite` versions omit themselves from the recorded trace, but are | |
361 | otherwise identical. Their primary purpose is to make some of the | |
362 | event context available to the event filters without having to commit | |
363 | the data to sub-buffers. See man:lttng-enable-event(1) to learn more | |
364 | about dynamic event filtering. | |
365 | ||
366 | See the <<example,EXAMPLE>> section below for a complete example. | |
367 | ||
368 | ||
369 | [[tracepoint-enum]] | |
370 | `TRACEPOINT_ENUM()` usage | |
371 | ~~~~~~~~~~~~~~~~~~~~~~~~~ | |
372 | An enumeration field is a list of mappings between an integers, or a | |
373 | range of integers, and strings (sometimes called _labels_ or | |
374 | _enumerators_). Enumeration fields can be used to have a more compact | |
375 | trace when the possible values for a field are limited. | |
376 | ||
377 | An enumeration field is defined with the `TRACEPOINT_ENUM()` macro: | |
378 | ||
379 | ------------------------------------------------------------------------ | |
380 | TRACEPOINT_ENUM( | |
381 | /* Tracepoint provider name */ | |
382 | my_provider, | |
383 | ||
384 | /* Enumeration name (unique in the whole tracepoint provider) */ | |
385 | my_enum, | |
386 | ||
387 | /* Enumeration mappings */ | |
388 | TP_ENUM_VALUES( | |
389 | ... | |
390 | ) | |
391 | ) | |
392 | ------------------------------------------------------------------------ | |
393 | ||
394 | `TP_ENUM_VALUES()` contains a list of enumeration mappings, :not: | |
395 | separated by commas. Two macros can be used in the `TP_ENUM_VALUES()`: | |
396 | `ctf_enum_value()` and `ctf_enum_range()`. | |
397 | ||
398 | `ctf_enum_value()` is a single value mapping: | |
399 | ||
400 | [verse] | |
401 | *ctf_enum_value*('label', 'value') | |
402 | ||
403 | This macro maps the given 'label' string to the value 'value'. | |
404 | ||
405 | `ctf_enum_range()` is a range mapping: | |
406 | ||
407 | [verse] | |
408 | *ctf_enum_range*('label', 'start', 'end') | |
409 | ||
410 | This macro maps the given 'label' string to the range of integers from | |
411 | 'start' to 'end', inclusively. Range mappings may overlap, but the | |
412 | behaviour is implementation-defined: each trace reader handles | |
413 | overlapping ranges as it wishes. | |
414 | ||
415 | See the <<example,EXAMPLE>> section below for a complete example. | |
416 | ||
417 | ||
418 | [[tracepoint-event-class]] | |
419 | `TRACEPOINT_EVENT_CLASS()` usage | |
420 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
421 | A *tracepoint class* is a class of tracepoints sharing the | |
422 | same field types and names. A tracepoint instance is one instance of | |
423 | such a declared tracepoint class, with its own event name. | |
424 | ||
425 | LTTng-UST creates one event serialization function per tracepoint | |
426 | class. Using `TRACEPOINT_EVENT()` creates one tracepoint class per | |
427 | tracepoint definition, whereas using `TRACEPOINT_EVENT_CLASS()` and | |
428 | `TRACEPOINT_EVENT_INSTANCE()` creates one tracepoint class, and one or | |
429 | more tracepoint instances of this class. In other words, many | |
430 | tracepoints can reuse the same serialization code. Reusing the same | |
431 | code, when possible, can reduce cache pollution, thus improve | |
432 | performance. | |
433 | ||
434 | The `TRACEPOINT_EVENT_CLASS()` macro accepts the same parameters as | |
435 | the `TRACEPOINT_EVENT()` macro, except that instead of an event name, | |
436 | its second parameter is the _tracepoint class name_: | |
437 | ||
438 | ------------------------------------------------------------------------ | |
439 | TRACEPOINT_EVENT_CLASS( | |
440 | /* Tracepoint provider name */ | |
441 | my_provider, | |
442 | ||
443 | /* Tracepoint class name */ | |
444 | my_tracepoint_class, | |
445 | ||
446 | /* List of tracepoint arguments (input) */ | |
447 | TP_ARGS( | |
448 | ... | |
449 | ), | |
450 | ||
451 | /* List of fields of eventual event (output) */ | |
452 | TP_FIELDS( | |
453 | ... | |
454 | ) | |
455 | ) | |
456 | ------------------------------------------------------------------------ | |
457 | ||
458 | Once the tracepoint class is defined, you can create as many tracepoint | |
459 | instances as needed: | |
460 | ||
461 | ------------------------------------------------------------------------- | |
462 | TRACEPOINT_EVENT_INSTANCE( | |
463 | /* Tracepoint provider name */ | |
464 | my_provider, | |
465 | ||
466 | /* Tracepoint class name */ | |
467 | my_tracepoint_class, | |
468 | ||
469 | /* Tracepoint/event name */ | |
470 | my_tracepoint, | |
471 | ||
472 | /* List of tracepoint arguments (input) */ | |
473 | TP_ARGS( | |
474 | ... | |
475 | ) | |
476 | ) | |
477 | ------------------------------------------------------------------------ | |
478 | ||
479 | As you can see, the `TRACEPOINT_EVENT_INSTANCE()` does not contain | |
480 | the `TP_FIELDS()` macro, because they are defined at the | |
481 | `TRACEPOINT_EVENT_CLASS()` level. | |
482 | ||
483 | See the <<example,EXAMPLE>> section below for a complete example. | |
484 | ||
485 | ||
486 | [[tracepoint-loglevel]] | |
487 | `TRACEPOINT_LOGLEVEL()` usage | |
488 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
489 | Optionally, a *log level* can be assigned to a defined tracepoint. | |
490 | Assigning different levels of severity to tracepoints can be useful: | |
491 | when controlling tracing sessions, you can choose to only enable | |
492 | events falling into a specific log level range using the | |
493 | nloption:--loglevel and nloption:--loglevel-only options of the | |
494 | man:lttng-enable-event(1) command. | |
495 | ||
496 | Log levels are assigned to tracepoints that are already defined using | |
497 | the `TRACEPOINT_LOGLEVEL()` macro. The latter must be used after having | |
498 | used `TRACEPOINT_EVENT()` or `TRACEPOINT_EVENT_INSTANCE()` for a given | |
499 | tracepoint. The `TRACEPOINT_LOGLEVEL()` macro is used as follows: | |
500 | ||
501 | ------------------------------------------------------------------------ | |
502 | TRACEPOINT_LOGLEVEL( | |
503 | /* Tracepoint provider name */ | |
504 | my_provider, | |
505 | ||
506 | /* Tracepoint/event name */ | |
507 | my_tracepoint, | |
508 | ||
509 | /* Log level */ | |
510 | TRACE_INFO | |
511 | ) | |
512 | ------------------------------------------------------------------------ | |
513 | ||
514 | The available log level definitions are: | |
515 | ||
516 | include::log-levels.txt[] | |
517 | ||
518 | See the <<example,EXAMPLE>> section below for a complete example. | |
519 | ||
520 | ||
521 | [[tracepoint]] | |
522 | Instrumenting your application | |
523 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
524 | Once the tracepoint provider is created (see the | |
525 | <<creating-tp,Creating a tracepoint provider>> section above), you can | |
526 | instrument your application with the defined tracepoints thanks to the | |
527 | `tracepoint()` macro: | |
528 | ||
529 | [verse] | |
530 | #define *tracepoint*('prov_name', 't_name', ...) | |
531 | ||
532 | With: | |
533 | ||
534 | 'prov_name':: | |
535 | Tracepoint provider name. | |
536 | ||
537 | 't_name':: | |
538 | Tracepoint/event name. | |
539 | ||
540 | `...`:: | |
541 | Tracepoint arguments, if any. | |
542 | ||
543 | Make sure to include the tracepoint provider header file anywhere you | |
544 | use `tracepoint()` for this provider. | |
545 | ||
546 | NOTE: Even though LTTng-UST supports `tracepoint()` call site duplicates | |
547 | having the same provider and tracepoint names, it is recommended to use | |
548 | a provider/tracepoint name pair only once within the application source | |
549 | code to help map events back to their call sites when analyzing the | |
550 | trace. | |
551 | ||
552 | Sometimes, arguments to the tracepoint are expensive to compute (take | |
553 | call stack, for example). To avoid the computation when the tracepoint | |
554 | is disabled, you can use the `tracepoint_enabled()` and | |
555 | `do_tracepoint()` macros: | |
556 | ||
557 | [verse] | |
558 | #define *tracepoint_enabled*('prov_name', 't_name') | |
559 | #define *do_tracepoint*('prov_name', 't_name', ...) | |
560 | ||
561 | `tracepoint_enabled()` returns a non-zero value if the tracepoint | |
562 | named 't_name' from the provider named 'prov_name' is enabled at | |
563 | run time. | |
564 | ||
565 | `do_tracepoint()` is like `tracepoint()`, except that it doesn't check | |
566 | if the tracepoint is enabled. Using `tracepoint()` with | |
567 | `tracepoint_enabled()` is dangerous since `tracepoint()` also contains | |
568 | the `tracepoint_enabled()` check, thus a race condition is possible | |
569 | in this situation: | |
570 | ||
571 | ------------------------------------------------------------------------ | |
572 | if (tracepoint_enabled(my_provider, my_tracepoint)) { | |
573 | stuff = prepare_stuff(); | |
574 | } | |
575 | ||
576 | tracepoint(my_provider, my_tracepoint, stuff); | |
577 | ------------------------------------------------------------------------ | |
578 | ||
579 | If the tracepoint is enabled after the condition, then `stuff` is not | |
580 | prepared: the emitted event will either contain wrong data, or the | |
581 | whole application could crash (segmentation fault, for example). | |
582 | ||
583 | NOTE: Neither `tracepoint_enabled()` nor `do_tracepoint()` have | |
584 | a `STAP_PROBEV()` call, so if you need it, you should emit this call | |
585 | yourself. | |
586 | ||
587 | ||
588 | [[build-static]] | |
589 | Statically linking the tracepoint provider | |
590 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
591 | With the static linking method, compiled tracepoint providers are copied | |
592 | into the target application. | |
593 | ||
594 | Define `TRACEPOINT_DEFINE` definition below the | |
595 | `TRACEPOINT_CREATE_PROBES` definition in the tracepoint provider | |
596 | source: | |
597 | ||
598 | ------------------------------------------------------------------------ | |
599 | #define TRACEPOINT_CREATE_PROBES | |
600 | #define TRACEPOINT_DEFINE | |
601 | ||
602 | #include "tp.h" | |
603 | ------------------------------------------------------------------------ | |
604 | ||
605 | Create the tracepoint provider object file: | |
606 | ||
607 | [role="term"] | |
608 | -------------- | |
609 | cc -c -I. tp.c | |
610 | -------------- | |
611 | ||
612 | NOTE: Although an application instrumented with LTTng-UST tracepoints | |
613 | can be compiled with a C++ compiler, tracepoint probes should be | |
614 | compiled with a C compiler. | |
615 | ||
616 | At this point, you _can_ archive this tracepoint provider object file, | |
617 | possibly with other object files of your application or with other | |
618 | tracepoint provider object files, as a static library: | |
619 | ||
620 | [role="term"] | |
621 | --------------- | |
622 | ar rc tp.a tp.o | |
623 | --------------- | |
624 | ||
625 | Using a static library does have the advantage of centralising the | |
626 | tracepoint providers objects so they can be shared between multiple | |
627 | applications. This way, when the tracepoint provider is modified, the | |
628 | source code changes don't have to be patched into each application's | |
629 | source code tree. The applications need to be relinked after each | |
630 | change, but need not to be otherwise recompiled (unless the tracepoint | |
631 | provider's API changes). | |
632 | ||
633 | Then, link your application with this object file (or with the static | |
634 | library containing it) and with `liblttng-ust` and `libdl` | |
635 | (`libc` on a BSD system): | |
636 | ||
637 | [role="term"] | |
638 | ------------------------------------- | |
639 | cc -o app tp.o app.o -llttng-ust -ldl | |
640 | ------------------------------------- | |
641 | ||
642 | ||
643 | [[build-dynamic]] | |
644 | Dynamically loading the tracepoint provider | |
645 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
646 | The second approach to package the tracepoint provider is to use the | |
647 | dynamic loader: the library and its member functions are explicitly | |
648 | sought, loaded at run time. | |
649 | ||
650 | In this scenario, the tracepoint provider is compiled as a shared | |
651 | object. | |
652 | ||
653 | The process to create the tracepoint provider shared object is pretty | |
654 | much the same as the <<build-static,static linking method>>, except | |
655 | that: | |
656 | ||
657 | * Since the tracepoint provider is not part of the application, | |
658 | `TRACEPOINT_DEFINE` must be defined, for each tracepoint | |
659 | provider, in exactly one source file of the | |
660 | _application_ | |
661 | * `TRACEPOINT_PROBE_DYNAMIC_LINKAGE` must be defined next | |
662 | to `TRACEPOINT_DEFINE` | |
663 | ||
664 | Regarding `TRACEPOINT_DEFINE` and `TRACEPOINT_PROBE_DYNAMIC_LINKAGE`, | |
665 | the recommended practice is to use a separate C source file in your | |
666 | application to define them, then include the tracepoint provider header | |
667 | files afterwards. For example, as `tp-define.c`: | |
668 | ||
669 | ------------------------------------------------------------------------ | |
670 | #define TRACEPOINT_DEFINE | |
671 | #define TRACEPOINT_PROBE_DYNAMIC_LINKAGE | |
672 | ||
673 | #include "tp.h" | |
674 | ------------------------------------------------------------------------ | |
675 | ||
676 | The tracepoint provider object file used to create the shared library is | |
677 | built like it is using the static linking method, but with the | |
678 | nloption:-fpic option: | |
679 | ||
680 | [role="term"] | |
681 | -------------------- | |
682 | cc -c -fpic -I. tp.c | |
683 | -------------------- | |
684 | ||
685 | It is then linked as a shared library like this: | |
686 | ||
687 | [role="term"] | |
688 | ------------------------------------------------------- | |
689 | cc -shared -Wl,--no-as-needed -o tp.so tp.o -llttng-ust | |
690 | ------------------------------------------------------- | |
691 | ||
692 | This tracepoint provider shared object isn't linked with the user | |
693 | application: it must be loaded manually. This is why the application is | |
694 | built with no mention of this tracepoint provider, but still needs | |
695 | libdl: | |
696 | ||
697 | [role="term"] | |
698 | -------------------------------- | |
699 | cc -o app app.o tp-define.o -ldl | |
700 | -------------------------------- | |
701 | ||
702 | There are two ways to dynamically load the tracepoint provider shared | |
703 | object: | |
704 | ||
705 | * Load it manually from the application using man:dlopen(3) | |
706 | * Make the dynamic loader load it with the `LD_PRELOAD` | |
707 | environment variable (see man:ld.so(8)) | |
708 | ||
709 | If the application does not dynamically load the tracepoint provider | |
710 | shared object using one of the methods above, tracing is disabled for | |
711 | this application, and the events are not listed in the output of | |
712 | man:lttng-list(1). | |
713 | ||
714 | Note that it is not safe to use man:dlclose(3) on a tracepoint provider | |
715 | shared object that is being actively used for tracing, due to a lack of | |
716 | reference counting from LTTng-UST to the shared object. | |
717 | ||
718 | For example, statically linking a tracepoint provider to a shared object | |
719 | which is to be dynamically loaded by an application (a plugin, for | |
720 | example) is not safe: the shared object, which contains the tracepoint | |
721 | provider, could be dynamically closed (man:dlclose(3)) at any time by | |
722 | the application. | |
723 | ||
724 | To instrument a shared object, either: | |
725 | ||
726 | * Statically link the tracepoint provider to the application, or | |
727 | * Build the tracepoint provider as a shared object (following the | |
728 | procedure shown in this section), and preload it when tracing is | |
729 | needed using the `LD_PRELOAD` environment variable. | |
730 | ||
731 | ||
732 | Using LTTng-UST with daemons | |
733 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
734 | Some extra care is needed when using `liblttng-ust` with daemon | |
735 | applications that call man:fork(2), man:clone(2), or BSD's man:rfork(2) | |
736 | without a following man:exec(3) family system call. The library | |
737 | `liblttng-ust-fork.so` needs to be preloaded before starting the | |
738 | application with the `LD_PRELOAD` environment variable (see | |
739 | man:ld.so(8)). | |
740 | ||
741 | ||
742 | Context information | |
743 | ~~~~~~~~~~~~~~~~~~~ | |
744 | Context information can be prepended by the LTTng-UST tracer before | |
745 | each event, or before specific events. | |
746 | ||
747 | Context fields can be added to specific channels using | |
748 | man:lttng-add-context(1). | |
749 | ||
750 | The following context fields are supported by LTTng-UST: | |
751 | ||
752 | `cpu_id`:: | |
753 | CPU ID. | |
754 | + | |
755 | NOTE: This context field is always enabled, and it cannot be added | |
756 | with man:lttng-add-context(1). Its main purpose is to be used for | |
757 | dynamic event filtering. See man:lttng-enable-event(1) for more | |
758 | information about event filtering. | |
759 | ||
760 | `ip`:: | |
761 | Instruction pointer: enables recording the exact address from which | |
762 | an event was emitted. This context field can be used to | |
763 | reverse-lookup the source location that caused the event | |
764 | to be emitted. | |
765 | ||
766 | +perf:thread:COUNTER+:: | |
767 | perf counter named 'COUNTER'. Use `lttng add-context --list` to | |
768 | list the available perf counters. | |
769 | + | |
770 | Only available on IA-32 and x86-64 architectures. | |
771 | ||
772 | `pthread_id`:: | |
773 | POSIX thread identifier. Can be used on architectures where | |
774 | `pthread_t` maps nicely to an `unsigned long` type. | |
775 | ||
776 | `procname`:: | |
777 | Thread name, as set by man:exec(3) or man:prctl(2). It is | |
778 | recommended that programs set their thread name with man:prctl(2) | |
779 | before hitting the first tracepoint for that thread. | |
780 | ||
781 | `vpid`:: | |
782 | Virtual process ID: process ID as seen from the point of view of | |
783 | the process namespace. | |
784 | ||
785 | `vtid`:: | |
786 | Virtual thread ID: thread ID as seen from the point of view of | |
787 | the process namespace. | |
788 | ||
789 | ||
174434f5 | 790 | [[state-dump]] |
4ddbd0b7 PP |
791 | LTTng-UST state dump |
792 | ~~~~~~~~~~~~~~~~~~~~ | |
793 | If an application that uses `liblttng-ust` becomes part of a tracing | |
794 | session, information about its currently loaded shared objects, their | |
0c3c03e0 | 795 | build IDs, and their debug link information are emitted as events |
4ddbd0b7 PP |
796 | by the tracer. |
797 | ||
798 | The following LTTng-UST state dump events exist and must be enabled | |
799 | to record application state dumps. | |
800 | ||
801 | `lttng_ust_statedump:start`:: | |
802 | Emitted when the state dump begins. | |
803 | + | |
804 | This event has no fields. | |
805 | ||
806 | `lttng_ust_statedump:end`:: | |
807 | Emitted when the state dump ends. Once this event is emitted, it | |
808 | is guaranteed that, for a given process, the state dump is | |
809 | complete. | |
810 | + | |
811 | This event has no fields. | |
812 | ||
6488ae4c | 813 | `lttng_ust_statedump:bin_info`:: |
f5eb039d AB |
814 | Emitted when information about a currently loaded executable or |
815 | shared object is found. | |
4ddbd0b7 PP |
816 | + |
817 | Fields: | |
818 | + | |
819 | [options="header"] | |
f5eb039d | 820 | |================================================================== |
4ddbd0b7 | 821 | | Field name | Description |
f5eb039d AB |
822 | | `baddr` | Base address of loaded executable |
823 | | `memsz` | Size of loaded executable in memory | |
6488ae4c | 824 | | `path` | Path to loaded executable file |
f5eb039d AB |
825 | | `is_pic` | Whether the executable is |
826 | position-independent code | |
827 | |================================================================== | |
4ddbd0b7 PP |
828 | |
829 | `lttng_ust_statedump:build_id`:: | |
830 | Emitted when a build ID is found in a currently loaded shared | |
831 | library. See | |
832 | https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] | |
833 | for more information about build IDs. | |
834 | + | |
835 | Fields: | |
836 | + | |
837 | [options="header"] | |
838 | |============================================================== | |
839 | | Field name | Description | |
840 | | `baddr` | Base address of loaded library | |
841 | | `build_id` | Build ID | |
842 | |============================================================== | |
843 | ||
844 | `lttng_ust_statedump:debug_link`:: | |
845 | Emitted when debug link information is found in a currently loaded | |
846 | shared library. See | |
847 | https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] | |
848 | for more information about debug links. | |
849 | + | |
850 | Fields: | |
851 | + | |
852 | [options="header"] | |
853 | |============================================================== | |
854 | | Field name | Description | |
855 | | `baddr` | Base address of loaded library | |
856 | | `crc` | Debug link file's CRC | |
857 | | `filename` | Debug link file name | |
858 | |============================================================== | |
859 | ||
860 | ||
861 | [[example]] | |
862 | EXAMPLE | |
863 | ------- | |
864 | NOTE: A few examples are available in the | |
865 | https://github.com/lttng/lttng-ust/tree/master/doc/examples[`doc/examples`] | |
866 | directory of LTTng-UST's source tree. | |
867 | ||
868 | This example shows all the features documented in the previous | |
869 | sections. The <<build-static,static linking>> method is chosen here | |
870 | to link the application with the tracepoint provider. | |
871 | ||
885adac8 PP |
872 | You can compile the source files and link them together statically |
873 | like this: | |
874 | ||
875 | [role="term"] | |
876 | ------------------------------------- | |
877 | cc -c -I. tp.c | |
878 | cc -c app.c | |
879 | cc -o app tp.o app.o -llttng-ust -ldl | |
880 | ------------------------------------- | |
881 | ||
00665d8e PP |
882 | Using the man:lttng(1) tool, create an LTTng tracing session, enable |
883 | all the events of this tracepoint provider, and start tracing: | |
884 | ||
885 | [role="term"] | |
886 | ---------------------------------------------- | |
887 | lttng create my-session | |
888 | lttng enable-event --userspace 'my_provider:*' | |
889 | lttng start | |
890 | ---------------------------------------------- | |
891 | ||
892 | You may also enable specific events: | |
893 | ||
894 | [role="term"] | |
895 | ---------------------------------------------------------- | |
896 | lttng enable-event --userspace my_provider:big_event | |
897 | lttng enable-event --userspace my_provider:event_instance2 | |
898 | ---------------------------------------------------------- | |
899 | ||
900 | Run the application: | |
901 | ||
902 | [role="term"] | |
903 | -------------------- | |
904 | ./app some arguments | |
905 | -------------------- | |
906 | ||
907 | Stop the current tracing session and inspect the recorded events: | |
908 | ||
909 | [role="term"] | |
910 | ---------- | |
911 | lttng stop | |
912 | lttng view | |
913 | ---------- | |
914 | ||
885adac8 PP |
915 | |
916 | Tracepoint provider header file | |
917 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
918 | `tp.h`: | |
4ddbd0b7 PP |
919 | |
920 | ------------------------------------------------------------------------ | |
921 | #undef TRACEPOINT_PROVIDER | |
922 | #define TRACEPOINT_PROVIDER my_provider | |
923 | ||
924 | #undef TRACEPOINT_INCLUDE | |
925 | #define TRACEPOINT_INCLUDE "./tp.h" | |
926 | ||
927 | #if !defined(_TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ) | |
928 | #define _TP_H | |
929 | ||
930 | #include <lttng/tracepoint.h> | |
931 | #include <stdio.h> | |
932 | ||
933 | #include "app.h" | |
934 | ||
935 | TRACEPOINT_EVENT( | |
936 | my_provider, | |
937 | simple_event, | |
938 | TP_ARGS( | |
939 | int, my_integer_arg, | |
940 | const char *, my_string_arg | |
941 | ), | |
942 | TP_FIELDS( | |
943 | ctf_string(argc, my_string_arg) | |
944 | ctf_integer(int, argv, my_integer_arg) | |
945 | ) | |
946 | ) | |
947 | ||
948 | TRACEPOINT_ENUM( | |
949 | my_provider, | |
950 | my_enum, | |
951 | TP_ENUM_VALUES( | |
952 | ctf_enum_value("ZERO", 0) | |
953 | ctf_enum_value("ONE", 1) | |
954 | ctf_enum_value("TWO", 2) | |
955 | ctf_enum_range("A RANGE", 52, 125) | |
956 | ctf_enum_value("ONE THOUSAND", 1000) | |
957 | ) | |
958 | ) | |
959 | ||
960 | TRACEPOINT_EVENT( | |
961 | my_provider, | |
962 | big_event, | |
963 | TP_ARGS( | |
964 | int, my_integer_arg, | |
965 | const char *, my_string_arg, | |
966 | FILE *, stream, | |
967 | double, flt_arg, | |
968 | int *, array_arg | |
969 | ), | |
970 | TP_FIELDS( | |
971 | ctf_integer(int, int_field1, my_integer_arg * 2) | |
972 | ctf_integer_hex(long int, stream_pos, ftell(stream)) | |
973 | ctf_float(double, float_field, flt_arg) | |
974 | ctf_string(string_field, my_string_arg) | |
975 | ctf_array(int, array_field, array_arg, 7) | |
976 | ctf_array_text(char, array_text_field, array_arg, 5) | |
977 | ctf_sequence(int, seq_field, array_arg, int, | |
978 | my_integer_arg / 10) | |
979 | ctf_sequence_text(char, seq_text_field, array_arg, | |
980 | int, my_integer_arg / 5) | |
981 | ctf_enum(my_provider, my_enum, int, | |
982 | enum_field, array_arg[1]) | |
983 | ) | |
984 | ) | |
985 | ||
986 | TRACEPOINT_LOGLEVEL(my_provider, big_event, TRACE_WARNING) | |
987 | ||
988 | TRACEPOINT_EVENT_CLASS( | |
989 | my_provider, | |
990 | my_tracepoint_class, | |
991 | TP_ARGS( | |
992 | int, my_integer_arg, | |
993 | struct app_struct *, app_struct_arg | |
994 | ), | |
995 | TP_FIELDS( | |
996 | ctf_integer(int, a, my_integer_arg) | |
997 | ctf_integer(unsigned long, b, app_struct_arg->b) | |
998 | ctf_string(c, app_struct_arg->c) | |
999 | ) | |
1000 | ) | |
1001 | ||
1002 | TRACEPOINT_EVENT_INSTANCE( | |
1003 | my_provider, | |
1004 | my_tracepoint_class, | |
1005 | event_instance1, | |
1006 | TP_ARGS( | |
1007 | int, my_integer_arg, | |
1008 | struct app_struct *, app_struct_arg | |
1009 | ) | |
1010 | ) | |
1011 | ||
1012 | TRACEPOINT_EVENT_INSTANCE( | |
1013 | my_provider, | |
1014 | my_tracepoint_class, | |
1015 | event_instance2, | |
1016 | TP_ARGS( | |
1017 | int, my_integer_arg, | |
1018 | struct app_struct *, app_struct_arg | |
1019 | ) | |
1020 | ) | |
1021 | ||
1022 | TRACEPOINT_LOGLEVEL(my_provider, event_instance2, TRACE_INFO) | |
1023 | ||
1024 | TRACEPOINT_EVENT_INSTANCE( | |
1025 | my_provider, | |
1026 | my_tracepoint_class, | |
1027 | event_instance3, | |
1028 | TP_ARGS( | |
1029 | int, my_integer_arg, | |
1030 | struct app_struct *, app_struct_arg | |
1031 | ) | |
1032 | ) | |
1033 | ||
1034 | #endif /* _TP_H */ | |
1035 | ||
1036 | #include <lttng/tracepoint-event.h> | |
1037 | ------------------------------------------------------------------------ | |
1038 | ||
885adac8 PP |
1039 | |
1040 | Tracepoint provider source file | |
1041 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1042 | `tp.c`: | |
4ddbd0b7 PP |
1043 | |
1044 | ------------------------------------------------------------------------ | |
1045 | #define TRACEPOINT_CREATE_PROBES | |
1046 | #define TRACEPOINT_DEFINE | |
1047 | ||
1048 | #include "tp.h" | |
1049 | ------------------------------------------------------------------------ | |
1050 | ||
885adac8 PP |
1051 | |
1052 | Application header file | |
1053 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1054 | `app.h`: | |
4ddbd0b7 PP |
1055 | |
1056 | ------------------------------------------------------------------------ | |
1057 | #ifndef _APP_H | |
1058 | #define _APP_H | |
1059 | ||
1060 | struct app_struct { | |
1061 | unsigned long b; | |
1062 | const char *c; | |
1063 | double d; | |
1064 | }; | |
1065 | ||
1066 | #endif /* _APP_H */ | |
1067 | ------------------------------------------------------------------------ | |
1068 | ||
885adac8 PP |
1069 | |
1070 | Application source file | |
1071 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1072 | `app.c`: | |
4ddbd0b7 PP |
1073 | |
1074 | ------------------------------------------------------------------------ | |
1075 | #include <stdlib.h> | |
1076 | #include <stdio.h> | |
1077 | ||
1078 | #include "tp.h" | |
1079 | #include "app.h" | |
1080 | ||
1081 | static int array_of_ints[] = { | |
1082 | 100, -35, 1, 23, 14, -6, 28, 1001, -3000, | |
1083 | }; | |
1084 | ||
1085 | int main(int argc, char* argv[]) | |
1086 | { | |
1087 | FILE *stream; | |
1088 | struct app_struct app_struct; | |
1089 | ||
1090 | tracepoint(my_provider, simple_event, argc, argv[0]); | |
1091 | stream = fopen("/tmp/app.txt", "w"); | |
1092 | ||
1093 | if (!stream) { | |
1094 | fprintf(stderr, | |
1095 | "Error: Cannot open /tmp/app.txt for writing\n"); | |
1096 | return EXIT_FAILURE; | |
1097 | } | |
1098 | ||
1099 | if (fprintf(stream, "0123456789") != 10) { | |
1100 | fclose(stream); | |
1101 | fprintf(stderr, "Error: Cannot write to /tmp/app.txt\n"); | |
1102 | return EXIT_FAILURE; | |
1103 | } | |
1104 | ||
1105 | tracepoint(my_provider, big_event, 35, "hello tracepoint", | |
1106 | stream, -3.14, array_of_ints); | |
1107 | fclose(stream); | |
1108 | app_struct.b = argc; | |
1109 | app_struct.c = "[the string]"; | |
1110 | tracepoint(my_provider, event_instance1, 23, &app_struct); | |
1111 | app_struct.b = argc * 5; | |
1112 | app_struct.c = "[other string]"; | |
1113 | tracepoint(my_provider, event_instance2, 17, &app_struct); | |
1114 | app_struct.b = 23; | |
1115 | app_struct.c = "nothing"; | |
1116 | tracepoint(my_provider, event_instance3, -52, &app_struct); | |
1117 | ||
1118 | return EXIT_SUCCESS; | |
1119 | } | |
1120 | ------------------------------------------------------------------------ | |
1121 | ||
4ddbd0b7 | 1122 | |
174434f5 PP |
1123 | ENVIRONMENT VARIABLES |
1124 | --------------------- | |
0ce82328 | 1125 | `LTTNG_HOME`:: |
14dd1c6f PP |
1126 | Alternative user's home directory. This variable is useful when the |
1127 | user running the instrumented application has a non-writable home | |
0ce82328 PP |
1128 | directory. |
1129 | + | |
1130 | Unix sockets used for the communication between `liblttng-ust` and the | |
1131 | LTTng session and consumer daemons (part of the LTTng-tools project) | |
1132 | are located in a specific directory under `$LTTNG_HOME` (or `$HOME` if | |
1133 | `$LTTNG_HOME` is not set). | |
1134 | ||
6f97f9c2 MD |
1135 | `LTTNG_UST_BLOCKING_RETRY_TIMEOUT`:: |
1136 | Maximum duration (milliseconds) to retry event tracing when | |
1137 | there's no space left for the event record in the sub-buffer. | |
1138 | + | |
1139 | -- | |
1140 | `0` (default):: | |
1141 | Never block the application. | |
1142 | ||
1143 | Positive value:: | |
1144 | Block the application for the specified number of milliseconds. If | |
1145 | there's no space left after this duration, discard the event | |
1146 | record. | |
1147 | ||
1148 | Negative value:: | |
1149 | Block the application until there's space left for the event record. | |
1150 | -- | |
1151 | + | |
1152 | This option can be useful in workloads generating very large trace data | |
1153 | throughput, where blocking the application is an acceptable trade-off to | |
1154 | prevent discarding event records. | |
1155 | + | |
1156 | WARNING: Setting this environment variable to a non-zero value may | |
1157 | significantly affect application timings. | |
1158 | ||
62c2f155 PP |
1159 | `LTTNG_UST_CLOCK_PLUGIN`:: |
1160 | Path to the shared object which acts as the clock override plugin. | |
1161 | An example of such a plugin can be found in the LTTng-UST | |
1162 | documentation under | |
1163 | https://github.com/lttng/lttng-ust/tree/master/doc/examples/clock-override[`examples/clock-override`]. | |
1164 | ||
174434f5 | 1165 | `LTTNG_UST_DEBUG`:: |
14dd1c6f | 1166 | Activates `liblttng-ust`'s debug and error output if set to `1`. |
174434f5 | 1167 | |
62c2f155 PP |
1168 | `LTTNG_UST_GETCPU_PLUGIN`:: |
1169 | Path to the shared object which acts as the `getcpu()` override | |
1170 | plugin. An example of such a plugin can be found in the LTTng-UST | |
1171 | documentation under | |
1172 | https://github.com/lttng/lttng-ust/tree/master/doc/examples/getcpu-override[`examples/getcpu-override`]. | |
1173 | ||
174434f5 | 1174 | `LTTNG_UST_REGISTER_TIMEOUT`:: |
14dd1c6f PP |
1175 | Waiting time for the _registration done_ session daemon command |
1176 | before proceeding to execute the main program (milliseconds). | |
174434f5 | 1177 | + |
14dd1c6f PP |
1178 | The value `0` means _do not wait_. The value `-1` means _wait forever_. |
1179 | Setting this environment variable to `0` is recommended for applications | |
174434f5 PP |
1180 | with time constraints on the process startup time. |
1181 | + | |
2b4444ce | 1182 | Default: {lttng_ust_register_timeout}. |
174434f5 | 1183 | |
6f97f9c2 MD |
1184 | `LTTNG_UST_BLOCKING_RETRY_TIMEOUT`:: |
1185 | Maximum time during which event tracing retry is attempted on buffer | |
1186 | full condition (millliseconds). Setting this environment to non-zero | |
1187 | value effectively blocks the application on buffer full condition. | |
1188 | Setting this environment variable to non-zero values may | |
1189 | significantly affect application timings. Setting this to a negative | |
1190 | value may block the application indefinitely if there is no consumer | |
1191 | emptying the ring buffer. The delay between retry attempts is the | |
1192 | minimum between the specified timeout value and 100ms. This option | |
1193 | can be useful in workloads generating very large trace data | |
1194 | throughput, where blocking the application is an acceptable | |
1195 | trade-off to not discard events. _Use with caution_. | |
1196 | + | |
1197 | The value `0` means _do not retry_. The value `-1` means _retry forever_. | |
1198 | Value > `0` means a maximum timeout of the given value. | |
1199 | + | |
1200 | Default: {lttng_ust_blocking_retry_timeout}. | |
1201 | ||
174434f5 | 1202 | `LTTNG_UST_WITHOUT_BADDR_STATEDUMP`:: |
14dd1c6f PP |
1203 | Prevents `liblttng-ust` from performing a base address state dump |
1204 | (see the <<state-dump,LTTng-UST state dump>> section above) if | |
1205 | set to `1`. | |
174434f5 | 1206 | |
174434f5 | 1207 | |
4ddbd0b7 PP |
1208 | include::common-footer.txt[] |
1209 | ||
1210 | include::common-copyrights.txt[] | |
1211 | ||
1212 | include::common-authors.txt[] | |
1213 | ||
1214 | ||
1215 | SEE ALSO | |
1216 | -------- | |
1217 | man:tracef(3), | |
1218 | man:tracelog(3), | |
1219 | man:lttng-gen-tp(1), | |
1220 | man:lttng-ust-dl(3), | |
1221 | man:lttng-ust-cyg-profile(3), | |
1222 | man:lttng(1), | |
1223 | man:lttng-enable-event(1), | |
1224 | man:lttng-list(1), | |
1225 | man:lttng-add-context(1), | |
1226 | man:babeltrace(1), | |
1227 | man:dlopen(3), | |
1228 | man:ld.so(8) |