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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 | |
23 | tracef() API. To you it, in a nutshell: | |
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 | ||
32 | 4) Enable the UST event "lttng_ust_tracef:event" when tracing with the | |
33 | following sequence of commands from lttng-tools: | |
34 | ||
35 | lttng create; lttng enable-event -u "lttng_ust_tracef:event"; lttng start | |
36 | [... run your program ...] | |
37 | lttng stop; lttng view | |
38 | ||
39 | That's it! | |
40 | ||
41 | If you want to have more flexibility and control on the event names, | |
42 | payload typing, etc, you can continue reading on and use the tracepoints | |
43 | below. "tracef()" is there for quick and dirty ad hoc instrumentation, | |
44 | whereas tracepoint.h is meant for thorough instrumentation of a code | |
45 | base to be integrated with an upstream project. | |
46 | .PP | |
47 | ||
48 | .SH "USAGE WITH TRACEPOINT" | |
eba411c6 MD |
49 | .PP |
50 | The simple way to generate the lttng-ust tracepoint probes is to use the | |
51 | lttng-gen-tp(1) tool. See the lttng-gen-tp(1) manpage for explanation. | |
52 | .PP | |
53 | ||
54 | .PP | |
55 | Here is the way to do it manually, without the lttng-gen-tp(1) helper | |
56 | script, through an example: | |
57 | .PP | |
58 | ||
59 | .SH "CREATION OF TRACEPOINT PROVIDER" | |
60 | ||
61 | .nf | |
62 | ||
63 | To create a tracepoint provider, within a build tree similar to | |
dfc45f18 MD |
64 | examples/easy-ust installed with lttng-ust documentation, see |
65 | sample_component_provider.h for the general layout. You will need to | |
66 | define TRACEPOINT_CREATE_PROBES before including your tracepoint | |
67 | provider probe in one source file of your application. See tp.c from | |
68 | easy-ust for an example of a tracepoint probe source file. This manpage | |
69 | will focus on the various types that can be recorded into a trace | |
70 | event: | |
eba411c6 MD |
71 | |
72 | TRACEPOINT_EVENT( | |
73 | /* | |
74 | * provider name, not a variable but a string starting with a | |
a106a9f8 | 75 | * letter and containing either letters, numbers or underscores. |
eba411c6 MD |
76 | * Needs to be the same as TRACEPOINT_PROVIDER. Needs to |
77 | * follow the namespacing guide-lines in lttng/tracepoint.h: | |
a106a9f8 JG |
78 | * |
79 | * Must be included before include tracepoint provider | |
eba411c6 MD |
80 | * ex.: project_event |
81 | * ex.: project_component_event | |
82 | * | |
83 | * Optional company name goes here | |
84 | * ex.: com_efficios_project_component_event | |
85 | * | |
86 | * In this example, "sample" is the project, and "component" is the | |
87 | * component. | |
88 | */ | |
89 | sample_component, | |
90 | ||
91 | /* | |
92 | * tracepoint name, same format as sample provider. Does not | |
93 | * need to be declared before. in this case the name is | |
a106a9f8 | 94 | * "message" |
eba411c6 MD |
95 | */ |
96 | message, | |
97 | ||
98 | /* | |
a106a9f8 | 99 | * TP_ARGS macro contains the arguments passed for the tracepoint |
eba411c6 MD |
100 | * it is in the following format |
101 | * TP_ARGS(type1, name1, type2, name2, ... type10, | |
102 | name10) | |
a106a9f8 JG |
103 | * where there can be from zero to ten elements. |
104 | * typeN is the datatype, such as int, struct or double **. | |
eba411c6 | 105 | * name is the variable name (in "int myInt" the name would be |
a106a9f8 | 106 | * myint) |
eba411c6 MD |
107 | * TP_ARGS() is valid to mean no arguments |
108 | * TP_ARGS(void) is valid too | |
109 | */ | |
110 | TP_ARGS(int, anint, int, netint, long *, values, | |
111 | char *, text, size_t, textlen, | |
112 | double, doublearg, float, floatarg), | |
113 | ||
114 | /* | |
a106a9f8 | 115 | * TP_FIELDS describes how to write the fields of the trace event. |
eba411c6 MD |
116 | * You can put expressions in the "argument expression" area, |
117 | * typically using the input arguments from TP_ARGS. | |
118 | */ | |
119 | TP_FIELDS( | |
120 | /* | |
121 | * ctf_integer: standard integer field. | |
122 | * args: (type, field name, argument expression) | |
123 | */ | |
124 | ctf_integer(int, intfield, anint) | |
125 | ctf_integer(long, longfield, anint) | |
126 | ||
127 | /* | |
128 | * ctf_integer_hex: integer field printed as hexadecimal. | |
129 | * args: (type, field name, argument expression) | |
130 | */ | |
131 | ctf_integer_hex(int, intfield2, anint) | |
132 | ||
133 | /* | |
134 | * ctf_integer_network: integer field in network byte | |
135 | * order. (_hex: printed as hexadecimal too) | |
136 | * args: (type, field name, argument expression) | |
137 | */ | |
138 | ctf_integer_network(int, netintfield, netint) | |
139 | ctf_integer_network_hex(int, netintfieldhex, netint) | |
140 | ||
141 | /* | |
142 | * ctf_array: a statically-sized array. | |
143 | * args: (type, field name, argument expression, value) | |
a106a9f8 | 144 | */ |
eba411c6 MD |
145 | ctf_array(long, arrfield1, values, 3) |
146 | ||
147 | /* | |
148 | * ctf_array_text: a statically-sized array, printed as | |
149 | * a string. No need to be terminated by a null | |
150 | * character. | |
2f65f1f5 | 151 | * Behavior is undefined if "text" argument is NULL. |
a106a9f8 | 152 | */ |
eba411c6 MD |
153 | ctf_array_text(char, arrfield2, text, 10) |
154 | ||
155 | /* | |
156 | * ctf_sequence: a dynamically-sized array. | |
157 | * args: (type, field name, argument expression, | |
158 | * type of length expression, length expression) | |
efbad5cc MD |
159 | * The "type of length expression" needs to be an |
160 | * unsigned type. As a reminder, "unsigned char" should | |
161 | * be preferred to "char", since the signedness of | |
162 | * "char" is implementation-defined. | |
2f65f1f5 | 163 | * Behavior is undefined if "text" argument is NULL. |
a106a9f8 | 164 | */ |
eba411c6 MD |
165 | ctf_sequence(char, seqfield1, text, |
166 | size_t, textlen) | |
167 | ||
168 | /* | |
169 | * ctf_sequence_text: a dynamically-sized array, printed | |
170 | * as string. No need to be null-terminated. | |
2f65f1f5 | 171 | * Behavior is undefined if "text" argument is NULL. |
eba411c6 MD |
172 | */ |
173 | ctf_sequence_text(char, seqfield2, text, | |
174 | size_t, textlen) | |
175 | ||
176 | /* | |
177 | * ctf_string: null-terminated string. | |
178 | * args: (field name, argument expression) | |
2f65f1f5 | 179 | * Behavior is undefined if "text" argument is NULL. |
eba411c6 MD |
180 | */ |
181 | ctf_string(stringfield, text) | |
182 | ||
183 | /* | |
184 | * ctf_float: floating-point number. | |
185 | * args: (type, field name, argument expression) | |
186 | */ | |
187 | ctf_float(float, floatfield, floatarg) | |
188 | ctf_float(double, doublefield, doublearg) | |
189 | ) | |
190 | ) | |
7d381d6e MD |
191 | |
192 | There can be an arbitrary number of tracepoint providers within an | |
193 | application, but they must each have their own provider name. Duplicate | |
194 | provider names are not allowed. | |
195 | ||
eba411c6 MD |
196 | .fi |
197 | ||
5883c06f MD |
198 | .SH "ASSIGNING LOGLEVEL TO EVENTS" |
199 | ||
200 | .nf | |
201 | ||
202 | Optionally, a loglevel can be assigned to a TRACEPOINT_EVENT using the | |
203 | following construct: | |
204 | ||
205 | TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >, | |
206 | < event >, < loglevel_name >) | |
207 | ||
7c501923 | 208 | The first field is the provider name, the second field is the name of |
5883c06f MD |
209 | the tracepoint, and the third field is the loglevel name. A |
210 | TRACEPOINT_EVENT should be declared prior to the the TRACEPOINT_LOGLEVEL | |
211 | for a given tracepoint name. The TRACEPOINT_PROVIDER must be already | |
212 | declared before declaring a TRACEPOINT_LOGLEVEL. | |
213 | ||
214 | The loglevels go from 0 to 14. Higher numbers imply the most verbosity | |
215 | (higher event throughput expected. | |
a106a9f8 | 216 | |
5883c06f MD |
217 | Loglevels 0 through 6, and loglevel 14, match syslog(3) loglevels |
218 | semantic. Loglevels 7 through 13 offer more fine-grained selection of | |
219 | debug information. | |
a106a9f8 | 220 | |
5883c06f MD |
221 | TRACE_EMERG 0 |
222 | system is unusable | |
a106a9f8 | 223 | |
5883c06f MD |
224 | TRACE_ALERT 1 |
225 | action must be taken immediately | |
a106a9f8 | 226 | |
5883c06f MD |
227 | TRACE_CRIT 2 |
228 | critical conditions | |
a106a9f8 | 229 | |
5883c06f MD |
230 | TRACE_ERR 3 |
231 | error conditions | |
a106a9f8 | 232 | |
5883c06f MD |
233 | TRACE_WARNING 4 |
234 | warning conditions | |
a106a9f8 | 235 | |
5883c06f MD |
236 | TRACE_NOTICE 5 |
237 | normal, but significant, condition | |
a106a9f8 | 238 | |
5883c06f MD |
239 | TRACE_INFO 6 |
240 | informational message | |
a106a9f8 | 241 | |
5883c06f MD |
242 | TRACE_DEBUG_SYSTEM 7 |
243 | debug information with system-level scope (set of programs) | |
a106a9f8 | 244 | |
5883c06f MD |
245 | TRACE_DEBUG_PROGRAM 8 |
246 | debug information with program-level scope (set of processes) | |
a106a9f8 | 247 | |
5883c06f MD |
248 | TRACE_DEBUG_PROCESS 9 |
249 | debug information with process-level scope (set of modules) | |
a106a9f8 | 250 | |
5883c06f MD |
251 | TRACE_DEBUG_MODULE 10 |
252 | debug information with module (executable/library) scope (set of | |
253 | units) | |
a106a9f8 | 254 | |
5883c06f MD |
255 | TRACE_DEBUG_UNIT 11 |
256 | debug information with compilation unit scope (set of functions) | |
a106a9f8 | 257 | |
5883c06f MD |
258 | TRACE_DEBUG_FUNCTION 12 |
259 | debug information with function-level scope | |
a106a9f8 | 260 | |
5883c06f MD |
261 | TRACE_DEBUG_LINE 13 |
262 | debug information with line-level scope (TRACEPOINT_EVENT default) | |
a106a9f8 | 263 | |
5883c06f MD |
264 | TRACE_DEBUG 14 |
265 | debug-level message (trace_printf default) | |
266 | ||
267 | See lttng(1) for information on how to use LTTng-UST loglevels. | |
268 | ||
269 | .fi | |
270 | ||
eba411c6 MD |
271 | .SH "ADDING TRACEPOINTS TO YOUR CODE" |
272 | ||
273 | .nf | |
274 | ||
275 | Include the provider header in each C files you plan to instrument, | |
276 | following the building/linking directives in the next section. | |
277 | ||
278 | For instance, add within a function: | |
279 | ||
280 | tracepoint(ust_tests_hello, tptest, i, netint, values, | |
281 | text, strlen(text), dbl, flt); | |
282 | ||
283 | As a call to the tracepoint. It will only be activated when requested by | |
284 | lttng(1) through lttng-sessiond(8). | |
285 | ||
d646ca64 MD |
286 | Even though LTTng-UST supports tracepoint() call site duplicates having |
287 | the same provider and event name, it is recommended to use a | |
288 | provider event name pair only once within the source code to help | |
7c501923 | 289 | map events back to their call sites when analyzing the trace. |
eba411c6 MD |
290 | .fi |
291 | ||
292 | .SH "BUILDING/LINKING THE TRACEPOINT PROVIDER" | |
293 | ||
294 | .nf | |
295 | There are 2 ways to compile the Tracepoint Provider with the | |
296 | application: either statically or dynamically. Please follow | |
297 | carefully: | |
298 | ||
299 | 1.1) Compile the Tracepoint provider with the application, either | |
300 | directly or through a static library (.a): | |
301 | - Into exactly one object of your application: define | |
302 | "TRACEPOINT_DEFINE" and include the tracepoint provider. | |
9b6435af | 303 | - Use "\-I." for the compilation unit containing the tracepoint |
eba411c6 | 304 | provider include (e.g. tp.c). |
9b6435af | 305 | - Link application with "\-ldl". |
eba411c6 | 306 | - If building the provider directly into the application, |
9b6435af | 307 | link the application with "\-llttng-ust". |
eba411c6 | 308 | - If building a static library for the provider, link the static |
38f5f440 | 309 | library with "\-llttng-ust". |
eba411c6 MD |
310 | - Include the tracepoint provider header into all C files using |
311 | the provider. | |
a106a9f8 JG |
312 | - Examples: |
313 | - doc/examples/easy-ust/ sample.c sample_component_provider.h tp.c | |
314 | Makefile | |
315 | - doc/examples/hello-static-lib/ hello.c tp.c ust_test_hello.h Makefile | |
eba411c6 MD |
316 | |
317 | 2) Compile the Tracepoint Provider separately from the application, | |
318 | using dynamic linking: | |
319 | - Into exactly one object of your application: define | |
320 | "TRACEPOINT_DEFINE" _and_ also define | |
321 | "TRACEPOINT_PROBE_DYNAMIC_LINKAGE", then include the tracepoint | |
322 | provider header. | |
323 | - Include the tracepoint provider header into all instrumented C | |
324 | files that use the provider. | |
9b6435af AM |
325 | - Compile the tracepoint provider with "\-I.". |
326 | - Link the tracepoint provider with "\-llttng-ust". | |
327 | - Link application with "\-ldl". | |
eba411c6 MD |
328 | - Set a LD_PRELOAD environment to preload the tracepoint provider |
329 | shared object before starting the application when tracing is | |
13fb2d2c JG |
330 | needed. Another way is to dlopen the tracepoint probe when needed |
331 | by the application. | |
eba411c6 | 332 | - Example: |
a106a9f8 | 333 | - doc/examples/demo demo.c tp*.c ust_tests_demo*.h demo-trace Makefile |
eba411c6 | 334 | |
13fb2d2c JG |
335 | - Note about dlclose() usage: it is not safe to use dlclose on a |
336 | provider shared object that is being actively used for tracing due | |
337 | to a lack of reference counting from lttng-ust to the used shared | |
338 | object. | |
eba411c6 MD |
339 | - Enable instrumentation and control tracing with the "lttng" command |
340 | from lttng-tools. See lttng-tools doc/quickstart.txt. | |
2bda849d MD |
341 | - Note for C++ support: although an application instrumented with |
342 | tracepoints can be compiled with g++, tracepoint probes should be | |
343 | compiled with gcc (only tested with gcc so far). | |
eba411c6 MD |
344 | |
345 | .fi | |
346 | ||
0a7c55a5 MD |
347 | .SH "USING LTTNG UST WITH DAEMONS" |
348 | ||
349 | .nf | |
350 | Some extra care is needed when using liblttng-ust with daemon | |
351 | applications that call fork(), clone(), or BSD rfork() without a | |
352 | following exec() family system call. The library "liblttng-ust-fork.so" | |
353 | needs to be preloaded for the application (launch with e.g. | |
354 | LD_PRELOAD=liblttng-ust-fork.so appname). | |
355 | ||
356 | .fi | |
357 | ||
94c9c48d MD |
358 | .SH "CONTEXT" |
359 | ||
360 | .PP | |
361 | Context information can be prepended by the tracer before each, or some, | |
362 | events. The following context information is supported by LTTng-UST: | |
363 | .PP | |
364 | ||
365 | .PP | |
366 | .IP "vtid" | |
367 | Virtual thread ID: thread ID as seen from the point of view of the | |
368 | process namespace. | |
369 | .PP | |
370 | ||
371 | .PP | |
372 | .IP "vpid" | |
373 | Virtual process ID: process ID as seen from the point of view of the | |
374 | process namespace. | |
375 | .PP | |
376 | ||
f6df8626 PW |
377 | .PP |
378 | .IP "ip" | |
379 | Instruction pointer: Enables recording of the exact location where a tracepoint | |
380 | was emitted. Can be used to reverse-lookup the source location that caused the | |
381 | event to be emitted. | |
382 | .PP | |
383 | ||
94c9c48d MD |
384 | .PP |
385 | .IP "procname" | |
386 | Thread name, as set by exec() or prctl(). It is recommended that | |
387 | programs set their thread name with prctl() before hitting the first | |
388 | tracepoint for that thread. | |
389 | .PP | |
390 | ||
391 | .PP | |
392 | .IP "pthread_id" | |
393 | Pthread identifier. Can be used on architectures where pthread_t maps | |
394 | nicely to an unsigned long type. | |
395 | .PP | |
396 | ||
b11abb67 | 397 | .SH "BASE ADDRESS STATEDUMP (Experimental feature)" |
f6df8626 PW |
398 | |
399 | .PP | |
b11abb67 PW |
400 | Warning: This is an experimental feature known to cause deadlocks when the |
401 | traced application uses fork, clone or daemon. Only use it for debugging and | |
402 | testing. Do NOT use it in production. | |
403 | ||
f6df8626 PW |
404 | If an application that uses liblttng-ust.so becomes part of a session, |
405 | information about its currently loaded shared objects will be traced to the | |
406 | session at session-enable time. To record this information, the following event | |
407 | needs to be enabled: | |
408 | .PP | |
409 | .IP "ust_baddr_statedump:soinfo" | |
410 | This event is used to trace a currently loaded shared object. The base address | |
411 | (where the dynamic linker has placed the shared object) is recorded in the | |
6d262185 MD |
412 | "baddr" field. The path to the shared object gets recorded in the |
413 | "sopath" field (as string). The file size of the loaded object (in | |
414 | bytes) is recorded to the "size" field and its time of last modification | |
415 | (in seconds since Epoch) is recorded in the "mtime" field. | |
f6df8626 | 416 | .PP |
6d262185 MD |
417 | If the event above is enabled, a series of "ust_baddr_statedump:soinfo" |
418 | events is recorded at session-enable time. It represents the state of | |
419 | currently loaded shared objects for the traced process. If this | |
420 | information gets combined with the lttng-ust-dl(3) instrumentation, all | |
421 | aspects of dynamic loading that are relevant for symbol and | |
422 | line number lookup are traced by LTTng. | |
f6df8626 | 423 | .PP |
eba411c6 MD |
424 | .SH "ENVIRONMENT VARIABLES" |
425 | ||
426 | .PP | |
427 | .IP "LTTNG_UST_DEBUG" | |
428 | Activate liblttng-ust debug output. | |
429 | .PP | |
430 | .IP "LTTNG_UST_REGISTER_TIMEOUT" | |
431 | The environment variable "LTTNG_UST_REGISTER_TIMEOUT" can be used to | |
432 | specify how long the applications should wait for sessiond | |
433 | "registration done" command before proceeding to execute the main | |
434 | program. The default is 3000ms (3 seconds). The timeout value is | |
435 | specified in milliseconds. The value 0 means "don't wait". The value | |
9b6435af | 436 | \-1 means "wait forever". Setting this environment variable to 0 is |
eba411c6 MD |
437 | recommended for applications with time constraints on the process |
438 | startup time. | |
439 | .PP | |
b11abb67 PW |
440 | .IP "LTTNG_UST_WITH_EXPERIMENTAL_BADDR_STATEDUMP" |
441 | Experimentally allow liblttng-ust to perform a base-address statedump on session-enable. | |
f6df8626 | 442 | .PP |
eba411c6 MD |
443 | |
444 | .SH "SEE ALSO" | |
445 | ||
446 | .PP | |
d1eaa4d7 | 447 | lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-ust-cyg-profile(3), |
f6df8626 | 448 | lttng-ust-dl(3), lttng-sessiond(8) |
eba411c6 | 449 | .PP |
ff42aeef MD |
450 | |
451 | .SH "COMPATIBILITY" | |
452 | ||
453 | .PP | |
454 | Older lttng-ust libraries reject more recent, and incompatible, probe | |
cf949d07 | 455 | providers. Newer lttng-ust libraries accept older probe providers, even |
ff42aeef MD |
456 | though some newer features might not be available with those providers. |
457 | .PP | |
458 | ||
eba411c6 MD |
459 | .SH "BUGS" |
460 | ||
461 | .PP | |
ff42aeef MD |
462 | LTTng-UST 2.0 and 2.1 lttng-ust libraries do not check for probe |
463 | provider version compatibility. This can lead to out-of-bound accesses | |
464 | when using a more recent probe provider with an older lttng-ust library. | |
465 | These error only trigger when tracing is active. This issue has been | |
466 | fixed in LTTng-UST 2.2. | |
eba411c6 MD |
467 | |
468 | If you encounter any issues or usability problem, please report it on | |
469 | our mailing list <lttng-dev@lists.lttng.org> to help improve this | |
470 | project. | |
471 | .SH "CREDITS" | |
472 | ||
473 | liblttng-ust is distributed under the GNU Lesser General Public License | |
474 | version 2.1. The headers are distributed under the MIT license. | |
475 | .PP | |
476 | See http://lttng.org for more information on the LTTng project. | |
477 | .PP | |
478 | Mailing list for support and development: <lttng-dev@lists.lttng.org>. | |
479 | .PP | |
480 | You can find us on IRC server irc.oftc.net (OFTC) in #lttng. | |
481 | .PP | |
482 | .SH "THANKS" | |
483 | ||
484 | Thanks to Ericsson for funding this work, providing real-life use-cases, | |
485 | and testing. | |
486 | ||
487 | Special thanks to Michel Dagenais and the DORSAL laboratory at | |
488 | Polytechnique de Montreal for the LTTng journey. | |
489 | .PP | |
490 | .SH "AUTHORS" | |
491 | ||
492 | .PP | |
493 | liblttng-ust was originally written by Mathieu Desnoyers, with additional | |
494 | contributions from various other people. It is currently maintained by | |
495 | Mathieu Desnoyers <mathieu.desnoyers@efficios.com>. | |
496 | .PP |