Update documentation for enable all events
[lttng-tools.git] / doc / quickstart.txt
1 NOTES:
2 --------------
3 2011-07-21 : User-space tracer is not released. Tracing in user-space at this
4 point is not possible with lttng-tools.
5
6 QUICKSTART
7 --------------
8
9 This is a quick start guide for the complete LTTng tool chain. This is divided
10 in three sections respectively kernel tracing, user-space tracing and reading a
11 trace.
12
13 See the README file for installation procedure or use the various Linux
14 distribution packages.
15
16 In order to trace the kernel, you'll need the lttng-modules >= 2.0 compiled and
17 installed. See http://lttng.org/lttng2.0 for more instructions for that part.
18 For user-space tracing, you'll need an instrumented application, please see
19 http://lttng.org/ust.
20
21 lttng-tools provide a session daemon (ltt-sessiond) that acts as a tracing
22 registry. To trace any instrumented applications or the kernel, a registered
23 tracing session is needed beforehand. To interact with the session daemon and a
24 tracing session, you should use the lttng command line UI (lttng).
25
26 Here is a list of some powerful features the LTTng 2.0 kernel tracer offers:
27
28 * Kprobes support
29 * Function Tracer support
30 * Context information support (add context data to an event)
31 * Perf counter support
32 * Tracepoint support
33
34 The next sections explain how to do tracing :)
35
36 Kernel Tracing
37 --------------
38
39 You can start the session daemon by invoking the command "ltt-sessiond",
40 or let the lttng command line tool do it for you. The session daemon
41 loads the LTTng tracer modules for you if those modules can be found on
42 your system. If they are not found, the kernel tracing feature will be
43 unavailable.
44
45 List available kernel events:
46
47 # lttng list -k
48
49 1) Create a tracing session. A .lttngrc will be created in $HOME containing
50 the session name (here 'mysession') you are working on.
51
52 # lttng create mysession
53
54 If you have multiple sessions, you can change the current session by using
55
56 # lttng set-session myothersession
57
58 2) Enable all tracepoints and all system call events.
59
60 # lttng enable-event -a -k
61
62 3) Enable tracepoint event(s). Here for example, we want only
63 'sched_switch' and 'sched_wakeup' events for the kernel (-k/--kernel).
64
65 # lttng enable-event sched_switch,sched_wakeup -k
66
67 or enable ALL tracepoint events:
68
69 # lttng enable-event -a -k --tracepoint
70
71 4) Enable all system call event(s).
72
73 # lttng enable-event -a -k --syscall
74
75 5) Enable kprobes and/or the function tracer with lttng
76
77 This is a new feature made possible by the new LTTng 2.0 kernel tracer. You can
78 enable a dynamic probe and data will be output in the trace along side with
79 your tracing data.
80
81 # lttng enable-event aname -k --probe symbol+0xffff7260695
82
83 or
84
85 # lttng enable-event aname -k --probe 0xffff7260695
86
87 Either an <address> or a <symbol+offset> can be used for probes.
88
89 You can also enable function tracer, which uses the Ftrace API (by Steven
90 Rostedt). Again, data will be output in the trace.
91
92 # lttng enable-event aname -k --function <symbol_name>
93
94 6) Enable context information for an event:
95
96 This is also a new feature which allows you to add context information to an
97 event. For example, you can add the PID along with the event information:
98
99 # lttng add-context -k -e sched_switch -t pid
100
101 At this point, you will have to look at 'lttng add-context --help' for all
102 possible context type which are integer values.
103
104 You can on the same line activate multiple context:
105
106 # lttng add-context -k -e sched_switch -t pid -t nice -t tid
107
108 7) Enable perf counter for an event:
109
110 Again, a new powerful feature is the possibility to add perf counter data
111 (using the perf API by Ingo Molnar and Thomas Gleixner) to the trace on a per
112 event basis. Let say we want to get the CPU cycles at each event:
113
114 # lttng add-context -k -e sched_switch -t perf:cpu-cycles
115
116 You'll have to use the add-context help for all possible perf counter values.
117
118 8) Start tracing:
119
120 # lttng start
121
122 Tracing is in progress at this point and traces will be written in
123 $HOME/lttng-traces/mysession-<date>-<time>
124
125 9) Stop tracing:
126
127 # lttng stop
128
129 Note: At this point, you can restart the trace (lttng start), enable/disable
130 events or just go take a break and come back 3 days later to start it again :).
131
132 10) Destroy your session after you are done with tracing
133
134 # lttng destroy
135
136 See Reading a trace section below to read you trace(s).
137
138 User-space Tracing
139 --------------
140
141 User-space tracer 2.0 not released at this point. For the 0.x versions,
142 you need to use 'ustctl' to control user-space tracing.
143
144 Reading a trace
145 --------------
146
147 The tool "Babeltrace" can be used to dump your binary trace into a
148 human-readable text format. Please see
149 http://www.efficios.com/babeltrace and git tree
150 http://git.efficios.com/?p=babeltrace.git
151
152 # babeltrace -n $HOME/lttng-traces/mysession-<date>-<time> | less
153
154 VoilĂ !
155
156 Please report any bugs/comments on our mailing list
157 (ltt-dev@lists.casi.polymtl.ca) or you can go on our IRC channel at
158 irc.oftc.net, channel #lttng
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