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1 | #LyX 1.6.1 created this file. For more info see http://www.lyx.org/ |
2 | \lyxformat 345 | |
3 | \begin_document | |
4 | \begin_header | |
5 | \textclass article | |
6 | \use_default_options true | |
7 | \language english | |
8 | \inputencoding auto | |
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20 | \use_hyperref false | |
21 | \papersize default | |
22 | \use_geometry false | |
23 | \use_amsmath 1 | |
24 | \use_esint 1 | |
25 | \cite_engine basic | |
26 | \use_bibtopic false | |
27 | \paperorientation portrait | |
28 | \secnumdepth 3 | |
29 | \tocdepth 3 | |
30 | \paragraph_separation indent | |
31 | \defskip medskip | |
32 | \quotes_language english | |
33 | \papercolumns 1 | |
34 | \papersides 1 | |
35 | \paperpagestyle default | |
36 | \tracking_changes false | |
37 | \output_changes false | |
38 | \author "" | |
39 | \end_header | |
40 | ||
41 | \begin_body | |
42 | ||
43 | \begin_layout Title | |
44 | LTTng Userspace Tracer Manual | |
45 | \end_layout | |
46 | ||
47 | \begin_layout Author | |
48 | Pierre-Marc Fournier | |
49 | \end_layout | |
50 | ||
51 | \begin_layout Section | |
52 | What is the LTTng Userspace Tracer? | |
53 | \end_layout | |
54 | ||
55 | \begin_layout Subsection | |
56 | Overview | |
57 | \end_layout | |
58 | ||
59 | \begin_layout Subsection | |
60 | Features | |
61 | \end_layout | |
62 | ||
63 | \begin_layout Itemize | |
64 | Arbitrary number of channels | |
65 | \end_layout | |
66 | ||
67 | \begin_layout Itemize | |
68 | One buffer per process (multiple threads share the same buffer) | |
69 | \end_layout | |
70 | ||
71 | \begin_layout Itemize | |
72 | Early process tracing (from the beginning of the main() function | |
73 | \end_layout | |
74 | ||
75 | \begin_layout Standard | |
76 | Still to implement: | |
77 | \end_layout | |
78 | ||
79 | \begin_layout Subsection | |
80 | Performance | |
81 | \end_layout | |
82 | ||
83 | \begin_layout Section | |
84 | Instrumenting an Application | |
85 | \end_layout | |
86 | ||
87 | \begin_layout Standard | |
88 | In order to record a trace of events occurring in a application, the application | |
89 | must be instrumented. | |
90 | Instrumentation points resemble function calls and | |
91 | \end_layout | |
92 | ||
93 | \begin_layout Standard | |
94 | There are no limitations on the type of code that may be instrumented. | |
95 | Multi-threaded programs may be instrumented without problem. | |
96 | Signal handler may be instrumented as well. | |
97 | \end_layout | |
98 | ||
99 | \begin_layout Standard | |
100 | There are two APIs to instrument programs: markers and tracepoints. | |
101 | Markers are quick to add and are usually used for temporary instrumentation. | |
102 | Tracepoints provide a way to instrument code more cleanly and are suited | |
103 | for permanent instrumentation. | |
104 | \end_layout | |
105 | ||
106 | \begin_layout Subsection | |
107 | Markers | |
108 | \end_layout | |
109 | ||
110 | \begin_layout Subsubsection | |
111 | Inserting Markers | |
112 | \end_layout | |
113 | ||
114 | \begin_layout Standard | |
115 | Adding a marker is simply a matter of insert one line in the program. | |
116 | \end_layout | |
117 | ||
118 | \begin_layout Standard | |
119 | \begin_inset listings | |
120 | inline false | |
121 | status open | |
122 | ||
123 | \begin_layout Plain Layout | |
124 | ||
125 | #include <marker.h> | |
126 | \end_layout | |
127 | ||
128 | \begin_layout Plain Layout | |
129 | ||
130 | void function() | |
131 | \end_layout | |
132 | ||
133 | \begin_layout Plain Layout | |
134 | ||
135 | { | |
136 | \end_layout | |
137 | ||
138 | \begin_layout Plain Layout | |
139 | ||
140 | int v; | |
141 | \end_layout | |
142 | ||
143 | \begin_layout Plain Layout | |
144 | ||
145 | char *st; | |
146 | \end_layout | |
147 | ||
148 | \begin_layout Plain Layout | |
149 | ||
150 | \end_layout | |
151 | ||
152 | \begin_layout Plain Layout | |
153 | ||
154 | /* ... | |
155 | set values of v and st ... | |
156 | */ | |
157 | \end_layout | |
158 | ||
159 | \begin_layout Plain Layout | |
160 | ||
161 | \end_layout | |
162 | ||
163 | \begin_layout Plain Layout | |
164 | ||
165 | /* a marker: */ | |
166 | \end_layout | |
167 | ||
168 | \begin_layout Plain Layout | |
169 | ||
170 | trace_mark(main, myevent, | |
171 | \begin_inset Quotes eld | |
172 | \end_inset | |
173 | ||
174 | firstarg %d secondarg %s | |
175 | \begin_inset Quotes erd | |
176 | \end_inset | |
177 | ||
178 | , v, st); | |
179 | \end_layout | |
180 | ||
181 | \begin_layout Plain Layout | |
182 | ||
183 | \end_layout | |
184 | ||
185 | \begin_layout Plain Layout | |
186 | ||
187 | /* a marker without arguments: */ | |
188 | \end_layout | |
189 | ||
190 | \begin_layout Plain Layout | |
191 | ||
192 | trace_mark(main, myotherevent, MARK_NOARGS); | |
193 | \end_layout | |
194 | ||
195 | \begin_layout Plain Layout | |
196 | ||
197 | } | |
198 | \end_layout | |
199 | ||
200 | \end_inset | |
201 | ||
202 | ||
203 | \end_layout | |
204 | ||
205 | \begin_layout Standard | |
206 | The invocation of the trace_mark() macro requires at least 3 arguments. | |
207 | The first, here | |
208 | \begin_inset Quotes eld | |
209 | \end_inset | |
210 | ||
211 | main | |
212 | \begin_inset Quotes erd | |
213 | \end_inset | |
214 | ||
215 | , is the name of the event category. | |
216 | It is also the name of the channel the event will go in. | |
217 | The second, here | |
218 | \begin_inset Quotes eld | |
219 | \end_inset | |
220 | ||
221 | myevent | |
222 | \begin_inset Quotes erd | |
223 | \end_inset | |
224 | ||
225 | is the name of the event. | |
226 | The third is a format string that announces the names and the types of | |
227 | the event arguments. | |
228 | Its format resembles that of a printf() format string; it is described | |
229 | thoroughly in Appendix x. | |
230 | \end_layout | |
231 | ||
232 | \begin_layout Standard | |
233 | A given Marker may appear more than once in the same program. | |
234 | Other Markers may have the same name and a different format string, although | |
235 | this might induce some confusion at analysis time. | |
236 | \end_layout | |
237 | ||
238 | \begin_layout Subsubsection | |
239 | Registering the Markers | |
240 | \end_layout | |
241 | ||
242 | \begin_layout Standard | |
243 | In order to inform to register the Markers present in the module, a macro | |
244 | must be inserted at global scope. | |
245 | Only one such macro is needed per exacutable or per shared object. | |
246 | Adding it more than once, however, is harmless. | |
247 | \end_layout | |
248 | ||
249 | \begin_layout Standard | |
250 | \begin_inset listings | |
251 | inline false | |
252 | status open | |
253 | ||
254 | \begin_layout Plain Layout | |
255 | ||
256 | MARKER_LIB; | |
257 | \end_layout | |
258 | ||
259 | \end_inset | |
260 | ||
261 | ||
262 | \end_layout | |
263 | ||
264 | \begin_layout Subsection | |
265 | Tracepoints | |
266 | \end_layout | |
267 | ||
268 | \begin_layout Standard | |
269 | The Tracepoints API uses the Markers, but provides a higher-level abstraction. | |
270 | Whereas the markers API provides limited type checking, the Tracepoints | |
271 | API provides more thorough type checking and discharges from the need to | |
272 | insert format strings directly in the code and to have format strings appear | |
273 | more than once if a given marker is reused. | |
274 | \end_layout | |
275 | ||
276 | \begin_layout Standard | |
277 | A tracepoint in the code looks like this: | |
278 | \end_layout | |
279 | ||
280 | \begin_layout Standard | |
281 | \begin_inset listings | |
282 | inline false | |
283 | status open | |
284 | ||
285 | \begin_layout Plain Layout | |
286 | ||
287 | #include <marker.h> | |
288 | \end_layout | |
289 | ||
290 | \begin_layout Plain Layout | |
291 | ||
292 | \end_layout | |
293 | ||
294 | \begin_layout Plain Layout | |
295 | ||
296 | void function() | |
297 | \end_layout | |
298 | ||
299 | \begin_layout Plain Layout | |
300 | ||
301 | { | |
302 | \end_layout | |
303 | ||
304 | \begin_layout Plain Layout | |
305 | ||
306 | int v; | |
307 | \end_layout | |
308 | ||
309 | \begin_layout Plain Layout | |
310 | ||
311 | char *st; | |
312 | \end_layout | |
313 | ||
314 | \begin_layout Plain Layout | |
315 | ||
316 | \end_layout | |
317 | ||
318 | \begin_layout Plain Layout | |
319 | ||
320 | /* ... | |
321 | set values of v and st ... | |
322 | */ | |
323 | \end_layout | |
324 | ||
325 | \begin_layout Plain Layout | |
326 | ||
327 | \end_layout | |
328 | ||
329 | \begin_layout Plain Layout | |
330 | ||
331 | /* a tracepoint: */ | |
332 | \end_layout | |
333 | ||
334 | \begin_layout Plain Layout | |
335 | ||
336 | trace_main_myevent(v, st); | |
337 | \end_layout | |
338 | ||
339 | \begin_layout Plain Layout | |
340 | ||
341 | } | |
342 | \end_layout | |
343 | ||
344 | \end_inset | |
345 | ||
346 | ||
347 | \end_layout | |
348 | ||
349 | \begin_layout Standard | |
350 | \begin_inset listings | |
351 | inline false | |
352 | status open | |
353 | ||
354 | \begin_layout Plain Layout | |
355 | ||
356 | DEFINE_TRACE(); | |
357 | \end_layout | |
358 | ||
359 | \end_inset | |
360 | ||
361 | ||
362 | \end_layout | |
363 | ||
364 | \begin_layout Standard | |
365 | \begin_inset listings | |
366 | inline false | |
367 | status open | |
368 | ||
369 | \begin_layout Plain Layout | |
370 | ||
371 | TRACEPOINT_LIB; | |
372 | \end_layout | |
373 | ||
374 | \end_inset | |
375 | ||
376 | ||
377 | \end_layout | |
378 | ||
379 | \begin_layout Subsection | |
380 | Compiling the Application | |
381 | \end_layout | |
382 | ||
383 | \begin_layout Section | |
384 | Recording a Trace | |
385 | \end_layout | |
386 | ||
387 | \begin_layout Subsection | |
388 | Basic Recording | |
389 | \end_layout | |
390 | ||
391 | \begin_layout Subsection | |
392 | Early Tracing | |
393 | \end_layout | |
394 | ||
395 | \begin_layout Section | |
396 | Viewing and Analyzing the Trace | |
397 | \end_layout | |
398 | ||
399 | \begin_layout Section | |
400 | Advanced Concepts | |
401 | \end_layout | |
402 | ||
403 | \begin_layout Subsection | |
404 | Using Custom Probes | |
405 | \end_layout | |
406 | ||
407 | \begin_layout Subsection | |
408 | Instrumenting Calls to Library Functions without Recompilation | |
409 | \end_layout | |
410 | ||
411 | \begin_layout Standard | |
412 | Calls to uninstrumented libraries may be instrumented by creating a wrapper | |
413 | library that intercepts calls to the library, trigger an instrumentation | |
414 | point. | |
415 | \end_layout | |
416 | ||
417 | \begin_layout Subsection | |
418 | Tracing Programs Without Linking them to the Tracing Library | |
419 | \end_layout | |
420 | ||
421 | \begin_layout Standard | |
422 | Programs that were not instrumented nor linked with the tracing libraries | |
423 | may still be traced. | |
424 | In order to produce events, they must be linked to instrumented libraries | |
425 | or use instrumented library wrappers as described in section xx. | |
426 | \end_layout | |
427 | ||
428 | \begin_layout Standard | |
429 | \begin_inset listings | |
430 | inline false | |
431 | status open | |
432 | ||
433 | \begin_layout Plain Layout | |
434 | ||
435 | LD_PRELOAD=... | |
436 | program | |
437 | \end_layout | |
438 | ||
439 | \end_inset | |
440 | ||
441 | ||
442 | \end_layout | |
443 | ||
444 | \begin_layout Section | |
445 | \start_of_appendix | |
446 | Format of Marker Format Strings | |
447 | \end_layout | |
448 | ||
449 | \end_body | |
450 | \end_document |