+NOTES:
+--------------
+
+2011-12-12: For user-space tracing, only the global UST domain ("-u" alone) is
+supported meaning that if you enable a tracepoint for user-space it will be
+enabled for all applications for the current tracing session you are working
+on.
+
QUICKSTART
--------------
This is a quick start guide for the complete LTTng tool chain. This is divided
-in three sections respectively Kernel tracing, user-space tracing and reading a
+in three sections respectively kernel tracing, user-space tracing and reading a
trace.
-See the README file for installation procedure or use the various Linux
+See the README.md file for installation procedure or use the various Linux
distribution packages.
-In order to trace the Kernel, you'll need the lttng-modules >= 2.0 compiled and
-installed. See http://lttng.org/content/lttng-kernel-tracer for more
-instructions for that part. For user-space tracing, you'll need an instrumented
-application, please see http://lttng.org/ust
+In order to trace the kernel, you'll need the lttng-modules 2.0 compiled and
+installed. See http://lttng.org/lttng2.0 for more instructions for that part.
+For user-space tracing, you'll need an instrumented application with lttng-ust
+2.0.
-lttng-tools provide a session daemon (ltt-sessiond) that acts as a tracing
+lttng-tools provide a session daemon (lttng-sessiond) that acts as a tracing
registry. To trace any instrumented applications or the kernel, a registered
-tracing session is needed.
+tracing session is needed beforehand. To interact with the session daemon and a
+tracing session, you should use the lttng command line UI (lttng). It is also
+possible to use the liblttngctl library for tracing control (lttng.h).
+
+Here is a list of some powerful features the LTTng 2.0 kernel tracer offers:
-To interact with the session daemon and a tracing session, you can use the
-lttng command line UI (lttng).
+ * Kprobes support
+ * Function Tracer support
+ * Context information support (add context data to an event)
+ * Perf counter support
+ * Tracepoint support
-The next sections explain how to do tracing :)
+And for the LTTng UST 2.0 tracer:
+
+ * Applications registration
+ * Automatic tracepoints activation upon app. registration
+ * Context information support
+ * Safe buffers after application crash
+ * Per-user tracing (root access *not* mandatory)
+
+The next sections explains how to do tracing :)
Kernel Tracing
--------------
-You have to modprobe the lttng-modules manually or the session daemon will do
-it for you if they can be found on your system.
+You can start the session daemon by invoking the command "lttng-sessiond", or
+let the lttng command line tool do it for you. The session daemon loads the
+LTTng tracer modules for you if those modules can be found on your system. If
+they are not found, the kernel tracing feature will be unavailable.
-You can then start the session daemon by hand or the lttng command line tool
-will do it for you.
-
-List possible kernel events:
+List available kernel events:
# lttng list -k
-1) Create a tracing session. A .lttngrc will be created in $HOME containing
-the session name (here 'mysession') you are working on.
+1) Create a tracing session. The .lttng directory will be created with .lttngrc
+file in $HOME containing the session name (here 'mysession') you are working
+on.
# lttng create mysession
-2) Enable event(s). Here for example, we want only 'sched_switch' and
-'sys_enter' events for the kernel (-k/--kernel).
+If you have multiple sessions, you can change the current session by using
-# lttng enable-event sched_switch,sys_enter -k
+# lttng set-session myothersession
-or enable ALL events (-a/--all):
+2) Enable all tracepoints and all system call events.
# lttng enable-event -a -k
-3) Start tracing:
+3) Enable tracepoint event(s). Here for example, we want only
+'sched_switch' and 'sched_wakeup' events for the kernel (-k/--kernel).
+
+# lttng enable-event sched_switch,sched_wakeup -k
+
+or enable ALL tracepoint events:
+
+# lttng enable-event -a -k --tracepoint
+
+4) Enable all system call event(s).
+
+# lttng enable-event -a -k --syscall
+
+5) Enable kprobes and/or the function tracer with lttng
+
+This is a new feature made possible by the new LTTng 2.0 kernel tracer. You can
+enable a dynamic probe and data will be output in the trace along side with
+your tracing data.
+
+# lttng enable-event aname -k --probe symbol+0x0
+
+or
+
+# lttng enable-event aname -k --probe 0xffff7260695
+
+Either an <address> or a <symbol+offset> can be used for probes.
+
+You can also enable function tracer, which uses the Ftrace API (by Steven
+Rostedt). Again, data will be output in the trace.
+
+# lttng enable-event aname -k --function <symbol_name>
+
+6) Enable context information for an event:
+
+This is also a new feature which allows you to add context information to an
+event. For example, you can add the PID along with the event information:
+
+# lttng add-context -k -e sched_switch -t pid
+
+At this point, you will have to look at 'lttng add-context --help' for all
+possible context type.
+
+You can on the same line activate multiple context:
+
+# lttng add-context -k -e sched_switch -t pid -t nice -t tid
+
+7) Enable perf counter for an event:
+
+Again, a new powerful feature is the possibility to add perf counter data
+(using the perf API by Ingo Molnar and Thomas Gleixner) to the trace on a per
+event basis. Let say we want to get the CPU cycles at each event:
+
+# lttng add-context -k -e sched_switch -t perf:cpu-cycles
+
+You'll have to use the add-context help for all possible perf counter values.
+
+8) Start tracing:
# lttng start
-Tracing is in progress at this point and will be written in
+Tracing is in progress at this point and traces will be written in
$HOME/lttng-traces/mysession-<date>-<time>
-4) Stop tracing:
+NOTE: It will start tracing for *all* domain(s).
+
+9) Stop tracing:
# lttng stop
-5) Destroy your session after you are done with tracing
+NOTE: At this point, you can restart the trace (lttng start), enable/disable
+events or just go take a break and come back 3 days later to start it again :).
+You can also read the trace since the buffers are flushed on stop command.
+
+10) Destroy your session after you are done with tracing
# lttng destroy
+See Reading a trace section below to read you trace(s).
+
User-space Tracing
--------------
-User-space tracer 2.0 not released at this point. For the 0.x versions,
-you need to use 'ustctl' to control user-space tracing.
+Like kernel tracing, you can start the session daemon by invoking the command
+"lttng-sessiond", or let the lttng command line tool do it for you.
+
+NOTE: You do *not* need root credentials in order to tracer user-space
+applications. However, if you run the session daemon under non-root user
+rights, only applications of that user will be traced.
+
+So, after instrumenting you applications with LTTng-ust 2.0
+(http://lttng.org/lttng2.0), upon startup, it will automatically register to
+the session daemon. If there is none running, it will simply wait on a seperate
+thread for a session daemon to appear and then register.
+
+Start your instrumented application at any time but at least before starting
+tracing :).
+
+List available registered applications:
+
+$ lttng list -u
+
+1) Create a tracing session. The .lttng directory will be created with a
+.lttngrc file in $HOME containing the session name (here 'mysession') you are
+working on.
+
+$ lttng create mysession
+
+If you have multiple sessions, you can change the current session by using:
+
+$ lttng set-session myothersession
+
+2) Enable all tracepoints for the global UST domain ("-u" alone).
+
+$ lttng enable-event -a -u
+
+or enable a single tracepoint event.
+
+$ lttng enable-event ust_tests_hello:tptest -u
+
+3) This is also a new feature which allows you to add context information to an
+event. For example, you can add the PID along with the event information:
+
+$ lttng add-context -t pid -e ust_tests_hello:tptest -u
+
+At this point, you will have to look at 'lttng add-context --help' for all
+possible context type.
+
+You can on the same line activate multiple context:
+
+$ lttng add-context -u -e ust_tests_hello:tptest -t pid -t nice -t tid
+
+4) Start tracing:
+
+$ lttng start
+
+Tracing is in progress at this point and traces will be written in the session
+directory.
+
+NOTE: It will start tracing for *all* domain(s).
+
+5) Stop tracing:
+
+$ lttng stop
+
+NOTE: At this point, you can restart the trace (lttng start), enable/disable
+events or just go take a break and come back 3 days later to start it again :).
+You can also read the trace since the buffers are flushed on stop command.
+
+6) Destroy your session after you are done with tracing
+
+$ lttng destroy
+
+See "Reading a trace" section below to read you trace(s).
+
Reading a trace
--------------
-To read your trace, you can use babeltrace which will text dump your the
-trace. Please see http://www.efficios.com/ctf and git tree
-http://git.efficios.com/?p=babeltrace.git
+The tool "Babeltrace" can be used to dump your binary trace into a
+human-readable text format. Please see http://www.efficios.com/babeltrace and
+git tree http://git.efficios.com/?p=babeltrace.git
-# babeltrace -n $HOME/lttng-traces/mysession-<date>-<time> | less
+# babeltrace $HOME/lttng-traces/mysession-<date>-<time> | less
Voilà!
+
+Please report any bugs/comments on our mailing list (lttng-dev@lists.lttng.org)
+or you can go on our IRC channel at irc.oftc.net, channel #lttng
projects / lttng-tools.git / blobdiff