1 .TH "LTTNG-UST" "3" "February 16, 2012" "" ""
4 lttng-ust \(em Linux Trace Toolkit Next Generation User-Space Tracer
10 Link liblttng-ust.so with applications, following this manpage.
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.
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.
27 Here is the way to do it manually, without the lttng-gen-tp(1) helper
28 script, through an example:
31 .SH "CREATION OF TRACEPOINT PROVIDER"
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:
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:
47 * Must be included before include tracepoint provider
49 * ex.: project_component_event
51 * Optional company name goes here
52 * ex.: com_efficios_project_component_event
54 * In this example, "sample" is the project, and "component" is the
60 * tracepoint name, same format as sample provider. Does not
61 * need to be declared before. in this case the name is
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,
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
75 * TP_ARGS() is valid to mean no arguments
76 * TP_ARGS(void) is valid too
78 TP_ARGS(int, anint, int, netint, long *, values,
79 char *, text, size_t, textlen,
80 double, doublearg, float, floatarg),
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.
89 * ctf_integer: standard integer field.
90 * args: (type, field name, argument expression)
92 ctf_integer(int, intfield, anint)
93 ctf_integer(long, longfield, anint)
96 * ctf_integer_hex: integer field printed as hexadecimal.
97 * args: (type, field name, argument expression)
99 ctf_integer_hex(int, intfield2, anint)
102 * ctf_integer_network: integer field in network byte
103 * order. (_hex: printed as hexadecimal too)
104 * args: (type, field name, argument expression)
106 ctf_integer_network(int, netintfield, netint)
107 ctf_integer_network_hex(int, netintfieldhex, netint)
110 * ctf_array: a statically-sized array.
111 * args: (type, field name, argument expression, value)
113 ctf_array(long, arrfield1, values, 3)
116 * ctf_array_text: a statically-sized array, printed as
117 * a string. No need to be terminated by a null
120 ctf_array_text(char, arrfield2, text, 10)
123 * ctf_sequence: a dynamically-sized array.
124 * args: (type, field name, argument expression,
125 * type of length expression, length expression)
127 ctf_sequence(char, seqfield1, text,
131 * ctf_sequence_text: a dynamically-sized array, printed
132 * as string. No need to be null-terminated.
134 ctf_sequence_text(char, seqfield2, text,
138 * ctf_string: null-terminated string.
139 * args: (field name, argument expression)
141 ctf_string(stringfield, text)
144 * ctf_float: floating-point number.
145 * args: (type, field name, argument expression)
147 ctf_float(float, floatfield, floatarg)
148 ctf_float(double, doublefield, doublearg)
153 .SH "ADDING TRACEPOINTS TO YOUR CODE"
157 Include the provider header in each C files you plan to instrument,
158 following the building/linking directives in the next section.
160 For instance, add within a function:
162 tracepoint(ust_tests_hello, tptest, i, netint, values,
163 text, strlen(text), dbl, flt);
165 As a call to the tracepoint. It will only be activated when requested by
166 lttng(1) through lttng-sessiond(8).
170 .SH "BUILDING/LINKING THE TRACEPOINT PROVIDER"
173 There are 2 ways to compile the Tracepoint Provider with the
174 application: either statically or dynamically. Please follow
177 1.1) Compile the Tracepoint provider with the application, either
178 directly or through a static library (.a):
179 - Into exactly one object of your application: define
180 "TRACEPOINT_DEFINE" and include the tracepoint provider.
181 - Use "-I." for the compilation unit containing the tracepoint
182 provider include (e.g. tp.c).
183 - Link application with "-ldl".
184 - If building the provider directly into the application,
185 link the application with "-llttng-ust".
186 - If building a static library for the provider, link the static
187 library with "-lllttng-ust".
188 - Include the tracepoint provider header into all C files using
191 tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example
193 2) Compile the Tracepoint Provider separately from the application,
194 using dynamic linking:
195 - Into exactly one object of your application: define
196 "TRACEPOINT_DEFINE" _and_ also define
197 "TRACEPOINT_PROBE_DYNAMIC_LINKAGE", then include the tracepoint
199 - Include the tracepoint provider header into all instrumented C
200 files that use the provider.
201 - Compile the tracepoint provider with "-I.".
202 - Link the tracepoint provider with "-llttng-ust".
203 - Link application with "-ldl".
204 - Set a LD_PRELOAD environment to preload the tracepoint provider
205 shared object before starting the application when tracing is
208 - tests/demo/ demo.c tp*.c ust_tests_demo*.h demo-trace
210 - Note about dlopen() usage: due to locking side-effects due to the
211 way libc lazily resolves Thread-Local Storage (TLS) symbols when a
212 library is dlopen'd, linking the tracepoint probe or liblttng-ust
213 with dlopen() is discouraged. They should be linked with the
214 application using "-llibname" or loaded with LD_PRELOAD.
215 - Enable instrumentation and control tracing with the "lttng" command
216 from lttng-tools. See lttng-tools doc/quickstart.txt.
220 .SH "ENVIRONMENT VARIABLES"
223 .IP "LTTNG_UST_DEBUG"
224 Activate liblttng-ust debug output.
226 .IP "LTTNG_UST_REGISTER_TIMEOUT"
227 The environment variable "LTTNG_UST_REGISTER_TIMEOUT" can be used to
228 specify how long the applications should wait for sessiond
229 "registration done" command before proceeding to execute the main
230 program. The default is 3000ms (3 seconds). The timeout value is
231 specified in milliseconds. The value 0 means "don't wait". The value
232 -1 means "wait forever". Setting this environment variable to 0 is
233 recommended for applications with time constraints on the process
240 lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-sessiond(8)
245 No knows bugs at this point.
247 If you encounter any issues or usability problem, please report it on
248 our mailing list <lttng-dev@lists.lttng.org> to help improve this
252 liblttng-ust is distributed under the GNU Lesser General Public License
253 version 2.1. The headers are distributed under the MIT license.
255 See http://lttng.org for more information on the LTTng project.
257 Mailing list for support and development: <lttng-dev@lists.lttng.org>.
259 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
263 Thanks to Ericsson for funding this work, providing real-life use-cases,
266 Special thanks to Michel Dagenais and the DORSAL laboratory at
267 Polytechnique de Montreal for the LTTng journey.
272 liblttng-ust was originally written by Mathieu Desnoyers, with additional
273 contributions from various other people. It is currently maintained by
274 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>.