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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 | |
15 | LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is | |
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 | ||
20 | .SH "USAGE" | |
21 | .PP | |
22 | The simple way to generate the lttng-ust tracepoint probes is to use the | |
23 | lttng-gen-tp(1) tool. See the lttng-gen-tp(1) manpage for explanation. | |
24 | .PP | |
25 | ||
26 | .PP | |
27 | Here is the way to do it manually, without the lttng-gen-tp(1) helper | |
28 | script, through an example: | |
29 | .PP | |
30 | ||
31 | .SH "CREATION OF TRACEPOINT PROVIDER" | |
32 | ||
33 | .nf | |
34 | ||
35 | To create a tracepoint provider, within a build tree similar to | |
36 | examples/easy-ust installed with lttng-ust documentation, a | |
37 | sample_component_provider.h for the general layout. This manpage will | |
38 | focus on the various types that can be recorded into a trace event: | |
39 | ||
40 | TRACEPOINT_EVENT( | |
41 | /* | |
42 | * provider name, not a variable but a string starting with a | |
43 | * letter and containing either letters, numbers or underscores. | |
44 | * Needs to be the same as TRACEPOINT_PROVIDER. Needs to | |
45 | * follow the namespacing guide-lines in lttng/tracepoint.h: | |
46 | * | |
47 | * Must be included before include tracepoint provider | |
48 | * ex.: project_event | |
49 | * ex.: project_component_event | |
50 | * | |
51 | * Optional company name goes here | |
52 | * ex.: com_efficios_project_component_event | |
53 | * | |
54 | * In this example, "sample" is the project, and "component" is the | |
55 | * component. | |
56 | */ | |
57 | sample_component, | |
58 | ||
59 | /* | |
60 | * tracepoint name, same format as sample provider. Does not | |
61 | * need to be declared before. in this case the name is | |
62 | * "message" | |
63 | */ | |
64 | message, | |
65 | ||
66 | /* | |
67 | * TP_ARGS macro contains the arguments passed for the tracepoint | |
68 | * it is in the following format | |
69 | * TP_ARGS(type1, name1, type2, name2, ... type10, | |
70 | name10) | |
71 | * where there can be from zero to ten elements. | |
72 | * typeN is the datatype, such as int, struct or double **. | |
73 | * name is the variable name (in "int myInt" the name would be | |
74 | * myint) | |
75 | * TP_ARGS() is valid to mean no arguments | |
76 | * TP_ARGS(void) is valid too | |
77 | */ | |
78 | TP_ARGS(int, anint, int, netint, long *, values, | |
79 | char *, text, size_t, textlen, | |
80 | double, doublearg, float, floatarg), | |
81 | ||
82 | /* | |
83 | * TP_FIELDS describes how to write the fields of the trace event. | |
84 | * You can put expressions in the "argument expression" area, | |
85 | * typically using the input arguments from TP_ARGS. | |
86 | */ | |
87 | TP_FIELDS( | |
88 | /* | |
89 | * ctf_integer: standard integer field. | |
90 | * args: (type, field name, argument expression) | |
91 | */ | |
92 | ctf_integer(int, intfield, anint) | |
93 | ctf_integer(long, longfield, anint) | |
94 | ||
95 | /* | |
96 | * ctf_integer_hex: integer field printed as hexadecimal. | |
97 | * args: (type, field name, argument expression) | |
98 | */ | |
99 | ctf_integer_hex(int, intfield2, anint) | |
100 | ||
101 | /* | |
102 | * ctf_integer_network: integer field in network byte | |
103 | * order. (_hex: printed as hexadecimal too) | |
104 | * args: (type, field name, argument expression) | |
105 | */ | |
106 | ctf_integer_network(int, netintfield, netint) | |
107 | ctf_integer_network_hex(int, netintfieldhex, netint) | |
108 | ||
109 | /* | |
110 | * ctf_array: a statically-sized array. | |
111 | * args: (type, field name, argument expression, value) | |
112 | */ | |
113 | ctf_array(long, arrfield1, values, 3) | |
114 | ||
115 | /* | |
116 | * ctf_array_text: a statically-sized array, printed as | |
117 | * a string. No need to be terminated by a null | |
118 | * character. | |
119 | */ | |
120 | ctf_array_text(char, arrfield2, text, 10) | |
121 | ||
122 | /* | |
123 | * ctf_sequence: a dynamically-sized array. | |
124 | * args: (type, field name, argument expression, | |
125 | * type of length expression, length expression) | |
efbad5cc MD |
126 | * The "type of length expression" needs to be an |
127 | * unsigned type. As a reminder, "unsigned char" should | |
128 | * be preferred to "char", since the signedness of | |
129 | * "char" is implementation-defined. | |
eba411c6 MD |
130 | */ |
131 | ctf_sequence(char, seqfield1, text, | |
132 | size_t, textlen) | |
133 | ||
134 | /* | |
135 | * ctf_sequence_text: a dynamically-sized array, printed | |
136 | * as string. No need to be null-terminated. | |
137 | */ | |
138 | ctf_sequence_text(char, seqfield2, text, | |
139 | size_t, textlen) | |
140 | ||
141 | /* | |
142 | * ctf_string: null-terminated string. | |
143 | * args: (field name, argument expression) | |
144 | */ | |
145 | ctf_string(stringfield, text) | |
146 | ||
147 | /* | |
148 | * ctf_float: floating-point number. | |
149 | * args: (type, field name, argument expression) | |
150 | */ | |
151 | ctf_float(float, floatfield, floatarg) | |
152 | ctf_float(double, doublefield, doublearg) | |
153 | ) | |
154 | ) | |
155 | .fi | |
156 | ||
5883c06f MD |
157 | .SH "ASSIGNING LOGLEVEL TO EVENTS" |
158 | ||
159 | .nf | |
160 | ||
161 | Optionally, a loglevel can be assigned to a TRACEPOINT_EVENT using the | |
162 | following construct: | |
163 | ||
164 | TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >, | |
165 | < event >, < loglevel_name >) | |
166 | ||
167 | The first field is the provider name, the second field is the name of | |
168 | the tracepoint, and the third field is the loglevel name. A | |
169 | TRACEPOINT_EVENT should be declared prior to the the TRACEPOINT_LOGLEVEL | |
170 | for a given tracepoint name. The TRACEPOINT_PROVIDER must be already | |
171 | declared before declaring a TRACEPOINT_LOGLEVEL. | |
172 | ||
173 | The loglevels go from 0 to 14. Higher numbers imply the most verbosity | |
174 | (higher event throughput expected. | |
175 | ||
176 | Loglevels 0 through 6, and loglevel 14, match syslog(3) loglevels | |
177 | semantic. Loglevels 7 through 13 offer more fine-grained selection of | |
178 | debug information. | |
179 | ||
180 | TRACE_EMERG 0 | |
181 | system is unusable | |
182 | ||
183 | TRACE_ALERT 1 | |
184 | action must be taken immediately | |
185 | ||
186 | TRACE_CRIT 2 | |
187 | critical conditions | |
188 | ||
189 | TRACE_ERR 3 | |
190 | error conditions | |
191 | ||
192 | TRACE_WARNING 4 | |
193 | warning conditions | |
194 | ||
195 | TRACE_NOTICE 5 | |
196 | normal, but significant, condition | |
197 | ||
198 | TRACE_INFO 6 | |
199 | informational message | |
200 | ||
201 | TRACE_DEBUG_SYSTEM 7 | |
202 | debug information with system-level scope (set of programs) | |
203 | ||
204 | TRACE_DEBUG_PROGRAM 8 | |
205 | debug information with program-level scope (set of processes) | |
206 | ||
207 | TRACE_DEBUG_PROCESS 9 | |
208 | debug information with process-level scope (set of modules) | |
209 | ||
210 | TRACE_DEBUG_MODULE 10 | |
211 | debug information with module (executable/library) scope (set of | |
212 | units) | |
213 | ||
214 | TRACE_DEBUG_UNIT 11 | |
215 | debug information with compilation unit scope (set of functions) | |
216 | ||
217 | TRACE_DEBUG_FUNCTION 12 | |
218 | debug information with function-level scope | |
219 | ||
220 | TRACE_DEBUG_LINE 13 | |
221 | debug information with line-level scope (TRACEPOINT_EVENT default) | |
222 | ||
223 | TRACE_DEBUG 14 | |
224 | debug-level message (trace_printf default) | |
225 | ||
226 | See lttng(1) for information on how to use LTTng-UST loglevels. | |
227 | ||
228 | .fi | |
229 | ||
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230 | .SH "ADDING TRACEPOINTS TO YOUR CODE" |
231 | ||
232 | .nf | |
233 | ||
234 | Include the provider header in each C files you plan to instrument, | |
235 | following the building/linking directives in the next section. | |
236 | ||
237 | For instance, add within a function: | |
238 | ||
239 | tracepoint(ust_tests_hello, tptest, i, netint, values, | |
240 | text, strlen(text), dbl, flt); | |
241 | ||
242 | As a call to the tracepoint. It will only be activated when requested by | |
243 | lttng(1) through lttng-sessiond(8). | |
244 | ||
d646ca64 MD |
245 | Even though LTTng-UST supports tracepoint() call site duplicates having |
246 | the same provider and event name, it is recommended to use a | |
247 | provider event name pair only once within the source code to help | |
248 | mapping events back to their call sites when analyzing the trace. | |
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249 | .fi |
250 | ||
251 | .SH "BUILDING/LINKING THE TRACEPOINT PROVIDER" | |
252 | ||
253 | .nf | |
254 | There are 2 ways to compile the Tracepoint Provider with the | |
255 | application: either statically or dynamically. Please follow | |
256 | carefully: | |
257 | ||
258 | 1.1) Compile the Tracepoint provider with the application, either | |
259 | directly or through a static library (.a): | |
260 | - Into exactly one object of your application: define | |
261 | "TRACEPOINT_DEFINE" and include the tracepoint provider. | |
9b6435af | 262 | - Use "\-I." for the compilation unit containing the tracepoint |
eba411c6 | 263 | provider include (e.g. tp.c). |
9b6435af | 264 | - Link application with "\-ldl". |
eba411c6 | 265 | - If building the provider directly into the application, |
9b6435af | 266 | link the application with "\-llttng-ust". |
eba411c6 | 267 | - If building a static library for the provider, link the static |
38f5f440 | 268 | library with "\-llttng-ust". |
eba411c6 MD |
269 | - Include the tracepoint provider header into all C files using |
270 | the provider. | |
271 | - Example: | |
13fb2d2c | 272 | - tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example |
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273 | |
274 | 2) Compile the Tracepoint Provider separately from the application, | |
275 | using dynamic linking: | |
276 | - Into exactly one object of your application: define | |
277 | "TRACEPOINT_DEFINE" _and_ also define | |
278 | "TRACEPOINT_PROBE_DYNAMIC_LINKAGE", then include the tracepoint | |
279 | provider header. | |
280 | - Include the tracepoint provider header into all instrumented C | |
281 | files that use the provider. | |
9b6435af AM |
282 | - Compile the tracepoint provider with "\-I.". |
283 | - Link the tracepoint provider with "\-llttng-ust". | |
284 | - Link application with "\-ldl". | |
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285 | - Set a LD_PRELOAD environment to preload the tracepoint provider |
286 | shared object before starting the application when tracing is | |
13fb2d2c JG |
287 | needed. Another way is to dlopen the tracepoint probe when needed |
288 | by the application. | |
eba411c6 | 289 | - Example: |
60302adc | 290 | - doc/examples/demo demo.c tp*.c ust_tests_demo*.h demo-trace |
eba411c6 | 291 | |
13fb2d2c JG |
292 | - Note about dlclose() usage: it is not safe to use dlclose on a |
293 | provider shared object that is being actively used for tracing due | |
294 | to a lack of reference counting from lttng-ust to the used shared | |
295 | object. | |
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296 | - Enable instrumentation and control tracing with the "lttng" command |
297 | from lttng-tools. See lttng-tools doc/quickstart.txt. | |
2bda849d MD |
298 | - Note for C++ support: although an application instrumented with |
299 | tracepoints can be compiled with g++, tracepoint probes should be | |
300 | compiled with gcc (only tested with gcc so far). | |
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301 | |
302 | .fi | |
303 | ||
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304 | .SH "USING LTTNG UST WITH DAEMONS" |
305 | ||
306 | .nf | |
307 | Some extra care is needed when using liblttng-ust with daemon | |
308 | applications that call fork(), clone(), or BSD rfork() without a | |
309 | following exec() family system call. The library "liblttng-ust-fork.so" | |
310 | needs to be preloaded for the application (launch with e.g. | |
311 | LD_PRELOAD=liblttng-ust-fork.so appname). | |
312 | ||
313 | .fi | |
314 | ||
94c9c48d MD |
315 | .SH "CONTEXT" |
316 | ||
317 | .PP | |
318 | Context information can be prepended by the tracer before each, or some, | |
319 | events. The following context information is supported by LTTng-UST: | |
320 | .PP | |
321 | ||
322 | .PP | |
323 | .IP "vtid" | |
324 | Virtual thread ID: thread ID as seen from the point of view of the | |
325 | process namespace. | |
326 | .PP | |
327 | ||
328 | .PP | |
329 | .IP "vpid" | |
330 | Virtual process ID: process ID as seen from the point of view of the | |
331 | process namespace. | |
332 | .PP | |
333 | ||
334 | .PP | |
335 | .IP "procname" | |
336 | Thread name, as set by exec() or prctl(). It is recommended that | |
337 | programs set their thread name with prctl() before hitting the first | |
338 | tracepoint for that thread. | |
339 | .PP | |
340 | ||
341 | .PP | |
342 | .IP "pthread_id" | |
343 | Pthread identifier. Can be used on architectures where pthread_t maps | |
344 | nicely to an unsigned long type. | |
345 | .PP | |
346 | ||
eba411c6 MD |
347 | .SH "ENVIRONMENT VARIABLES" |
348 | ||
349 | .PP | |
350 | .IP "LTTNG_UST_DEBUG" | |
351 | Activate liblttng-ust debug output. | |
352 | .PP | |
353 | .IP "LTTNG_UST_REGISTER_TIMEOUT" | |
354 | The environment variable "LTTNG_UST_REGISTER_TIMEOUT" can be used to | |
355 | specify how long the applications should wait for sessiond | |
356 | "registration done" command before proceeding to execute the main | |
357 | program. The default is 3000ms (3 seconds). The timeout value is | |
358 | specified in milliseconds. The value 0 means "don't wait". The value | |
9b6435af | 359 | \-1 means "wait forever". Setting this environment variable to 0 is |
eba411c6 MD |
360 | recommended for applications with time constraints on the process |
361 | startup time. | |
362 | .PP | |
363 | ||
364 | .SH "SEE ALSO" | |
365 | ||
366 | .PP | |
d1eaa4d7 PW |
367 | lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-ust-cyg-profile(3), |
368 | lttng-sessiond(8) | |
eba411c6 MD |
369 | .PP |
370 | .SH "BUGS" | |
371 | ||
372 | .PP | |
60302adc | 373 | No known bugs at this point. |
eba411c6 MD |
374 | |
375 | If you encounter any issues or usability problem, please report it on | |
376 | our mailing list <lttng-dev@lists.lttng.org> to help improve this | |
377 | project. | |
378 | .SH "CREDITS" | |
379 | ||
380 | liblttng-ust is distributed under the GNU Lesser General Public License | |
381 | version 2.1. The headers are distributed under the MIT license. | |
382 | .PP | |
383 | See http://lttng.org for more information on the LTTng project. | |
384 | .PP | |
385 | Mailing list for support and development: <lttng-dev@lists.lttng.org>. | |
386 | .PP | |
387 | You can find us on IRC server irc.oftc.net (OFTC) in #lttng. | |
388 | .PP | |
389 | .SH "THANKS" | |
390 | ||
391 | Thanks to Ericsson for funding this work, providing real-life use-cases, | |
392 | and testing. | |
393 | ||
394 | Special thanks to Michel Dagenais and the DORSAL laboratory at | |
395 | Polytechnique de Montreal for the LTTng journey. | |
396 | .PP | |
397 | .SH "AUTHORS" | |
398 | ||
399 | .PP | |
400 | liblttng-ust was originally written by Mathieu Desnoyers, with additional | |
401 | contributions from various other people. It is currently maintained by | |
402 | Mathieu Desnoyers <mathieu.desnoyers@efficios.com>. | |
403 | .PP |