.SH "DESCRIPTION"
.PP
-LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is
+LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is a
port of the low-overhead tracing capabilities of the LTTng kernel tracer
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 the UST event "lttng_ust_tracef:event" when tracing with the
+ following sequence of commands from lttng-tools:
+
+ lttng create; lttng enable-event -u "lttng_ust_tracef:event"; 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.
.nf
To create a tracepoint provider, within a build tree similar to
-examples/easy-ust installed with lttng-ust documentation, a
-sample_component_provider.h for the general layout. This manpage will
-focus on the various types that can be recorded into a trace event:
+examples/easy-ust installed with lttng-ust documentation, see
+sample_component_provider.h for the general layout. You will need to
+define TRACEPOINT_CREATE_PROBES before including your tracepoint
+provider probe in one source file of your application. See tp.c from
+easy-ust for an example of a tracepoint probe source file. This manpage
+will focus on the various types that can be recorded into a trace
+event:
TRACEPOINT_EVENT(
/*
ctf_float(double, doublefield, doublearg)
)
)
+
+There can be an arbitrary number of tracepoint providers within an
+application, but they must each have their own provider name. Duplicate
+provider names are not allowed.
+
.fi
.SH "ASSIGNING LOGLEVEL TO EVENTS"
TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >,
< event >, < loglevel_name >)
- The first field is the provider name, the second field is the name of
+The first field is the provider name, the second field is the name of
the tracepoint, and the third field is the loglevel name. A
TRACEPOINT_EVENT should be declared prior to the the TRACEPOINT_LOGLEVEL
for a given tracepoint name. The TRACEPOINT_PROVIDER must be already
Even though LTTng-UST supports tracepoint() call site duplicates having
the same provider and event name, it is recommended to use a
provider event name pair only once within the source code to help
-mapping events back to their call sites when analyzing the trace.
+map events back to their call sites when analyzing the trace.
.fi
.SH "BUILDING/LINKING THE TRACEPOINT PROVIDER"
process namespace.
.PP
+.PP
+.IP "ip"
+Instruction pointer: Enables recording of the exact location where a tracepoint
+was emitted. Can be used to reverse-lookup the source location that caused the
+event to be emitted.
+.PP
+
.PP
.IP "procname"
Thread name, as set by exec() or prctl(). It is recommended that
nicely to an unsigned long type.
.PP
+.SH "BASE ADDRESS STATEDUMP (Experimental feature)"
+
+.PP
+Warning: This is an experimental feature known to cause deadlocks when the
+traced application uses fork, clone or daemon. Only use it for debugging and
+testing. Do NOT use it in production.
+
+If an application that uses liblttng-ust.so becomes part of a session,
+information about its currently loaded shared objects will be traced to the
+session at session-enable time. To record this information, the following event
+needs to be enabled:
+.PP
+.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. 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
recommended for applications with time constraints on the process
startup time.
.PP
+.IP "LTTNG_UST_WITH_EXPERIMENTAL_BADDR_STATEDUMP"
+Experimentally allow liblttng-ust to perform a base-address statedump on session-enable.
+.PP
.SH "SEE ALSO"
.PP
lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-ust-cyg-profile(3),
-lttng-sessiond(8)
+lttng-ust-dl(3), lttng-sessiond(8)
.PP
.SH "COMPATIBILITY"
.PP
Older lttng-ust libraries reject more recent, and incompatible, probe
-providers. Newer lttng-ust librairies accept older probe providers, even
+providers. Newer lttng-ust libraries accept older probe providers, even
though some newer features might not be available with those providers.
.PP
projects / lttng-ust.git / blobdiff