to user-space. The library "liblttng-ust" enables tracing of
applications and libraries.
-.SH "USAGE"
+.SH "USAGE WITH TRACEF"
+.PP
+The simplest way to add instrumentation to your code is by far the
+tracef() API. To do it, in a nutshell:
+
+1) #include <lttng/tracef.h>
+
+2) /* in your code, use like a printf */
+ tracef("my message, this integer %d", 1234);
+
+3) Link your program against liblttng-ust.so.
+
+4) Enable UST events when tracing with the following sequence of commands
+ from lttng-tools:
+
+ lttng create
+ lttng enable-event -u -a
+ lttng start
+ [... run your program ...]
+ lttng stop
+ lttng view
+
+That's it!
+
+If you want to have more flexibility and control on the event names,
+payload typing, etc, you can continue reading on and use the tracepoints
+below. "tracef()" is there for quick and dirty ad hoc instrumentation,
+whereas tracepoint.h is meant for thorough instrumentation of a code
+base to be integrated with an upstream project.
+.PP
+
+.SH "USAGE WITH TRACEPOINT"
.PP
The simple way to generate the lttng-ust tracepoint probes is to use the
lttng-gen-tp(1) tool. See the lttng-gen-tp(1) manpage for explanation.
sample_component,
/*
- * tracepoint name, same format as sample provider. Does not
- * need to be declared before. in this case the name is
- * "message"
+ * tracepoint name, characters permitted follow the same
+ * constraints as the provider name. The name of this example
+ * event is "sample_event".
*/
- message,
+ sample_event,
/*
* TP_ARGS macro contains the arguments passed for the tracepoint
debug information with line-level scope (TRACEPOINT_EVENT default)
TRACE_DEBUG 14
- debug-level message (trace_printf default)
+ debug-level message
See lttng(1) for information on how to use LTTng-UST loglevels.
application: either statically or dynamically. Please follow
carefully:
- 1.1) Compile the Tracepoint provider with the application, either
- directly or through a static library (.a):
- - Into exactly one object of your application: define
+ 1) Compile the Tracepoint Provider with the application, either
+ directly or through a static library (.a):
+ - Into exactly one object of your application, define
"TRACEPOINT_DEFINE" and include the tracepoint provider.
- Use "\-I." for the compilation unit containing the tracepoint
- provider include (e.g. tp.c).
- - Link application with "\-ldl".
- - If building the provider directly into the application,
- link the application with "\-llttng-ust".
- - If building a static library for the provider, link the static
- library with "\-llttng-ust".
+ provider include (e.g., tp.c).
+ - Link the application with "\-llttng-ust" and "\-ldl".
- Include the tracepoint provider header into all C files using
the provider.
- Examples:
.IP "ust_baddr_statedump:soinfo"
This event is used to trace a currently loaded shared object. The base address
(where the dynamic linker has placed the shared object) is recorded in the
-baddr-field. The path to the shared object gets recorded in the sopath-field
-(as string). The file size of the loaded object (in bytes) is recorded to the
-size-field and its time of last modification (in seconds since Epoch) is
-recorded in the mtime-field.
-.PP
-If the event above is enabled, a series of ust_baddr_statedump:soinfo events is
-recorded at session-enable time, that represents the state of currently loaded
-shared objects (of the traced application). If this information gets combined
-with the lttng-ust-dl(3) instrumentation, all aspects of dynamic loading that
-are relevant for symbol and linenumber-lookup are traced by LTTng.
+"baddr" field. The path to the shared object gets recorded in the
+"sopath" field (as string). The file size of the loaded object (in
+bytes) is recorded to the "size" field and its time of last modification
+(in seconds since Epoch) is recorded in the "mtime" field.
+.PP
+If the event above is enabled, a series of "ust_baddr_statedump:soinfo"
+events is recorded at session-enable time. It represents the state of
+currently loaded shared objects for the traced process. If this
+information gets combined with the lttng-ust-dl(3) instrumentation, all
+aspects of dynamic loading that are relevant for symbol and
+line number lookup are traced by LTTng.
.PP
.SH "ENVIRONMENT VARIABLES"
.PP
.IP "LTTNG_UST_DEBUG"
-Activate liblttng-ust debug output.
+Activate liblttng-ust debug and error output.
.PP
.IP "LTTNG_UST_REGISTER_TIMEOUT"
The environment variable "LTTNG_UST_REGISTER_TIMEOUT" can be used to