Missing -k option in quickstart guide
[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 event(s). Here for example, we want only 'sched_switch' and
59 'sys_enter' events for the kernel (-k/--kernel).
60
61 # lttng enable-event sched_switch,sys_enter -k
62
63 or enable ALL events (-a/--all):
64
65 # lttng enable-event -a -k
66
67 3) Enable kprobes and/or the function tracer with lttng
68
69 This is a new feature made possible by the new LTTng 2.0 kernel tracer. You can
70 enable a dynamic probe and data will be output in the trace along side with
71 your tracing data.
72
73 # lttng enable-event aname -k --probe symbol+0xffff7260695
74
75 or
76
77 # lttng enable-event aname -k --probe 0xffff7260695
78
79 Either an <address> or a <symbol+offset> can be used for probes.
80
81 You can also enable function tracer, which uses the Ftrace API (by Steven
82 Rostedt). Again, data will be output in the trace.
83
84 # lttng enable-event aname -k --function <symbol_name>
85
86 4) Enable context information for an event:
87
88 This is also a new feature which allows you to add context information to an
89 event. For example, you can add the PID along with the event information:
90
91 # lttng add-context -k -e sched_switch -t pid
92
93 At this point, you will have to look at 'lttng add-context --help' for all
94 possible context type which are integer values.
95
96 You can on the same line activate multiple context:
97
98 # lttng add-context -k -e sched_switch -t pid -t nice -t tid
99
100 5) Enable perf counter for an event:
101
102 Again, a new powerful feature is the possibility to add perf counter data
103 (using the perf API by Ingo Molnar and Thomas Gleixner) to the trace on a per
104 event basis. Let say we want to get the CPU cycles at each event:
105
106 # lttng add-context -k -e sched_switch -t perf:cpu-cycles
107
108 You'll have to use the add-context help for all possible perf counter values.
109
110 6) Start tracing:
111
112 # lttng start
113
114 Tracing is in progress at this point and traces will be written in
115 $HOME/lttng-traces/mysession-<date>-<time>
116
117 7) Stop tracing:
118
119 # lttng stop
120
121 Note: At this point, you can restart the trace (lttng start), enable/disable
122 events or just go take a break and come back 3 days later to start it again :).
123
124 8) Destroy your session after you are done with tracing
125
126 # lttng destroy
127
128 See Reading a trace section below to read you trace(s).
129
130 User-space Tracing
131 --------------
132
133 User-space tracer 2.0 not released at this point. For the 0.x versions,
134 you need to use 'ustctl' to control user-space tracing.
135
136 Reading a trace
137 --------------
138
139 The tool "Babeltrace" can be used to dump your binary trace into a
140 human-readable text format. Please see
141 http://www.efficios.com/babeltrace and git tree
142 http://git.efficios.com/?p=babeltrace.git
143
144 # babeltrace -n $HOME/lttng-traces/mysession-<date>-<time> | less
145
146 VoilĂ !
147
148 Please report any bugs/comments on our mailing list
149 (ltt-dev@lists.casi.polymtl.ca) or you can go on our IRC channel at
150 irc.oftc.net, channel #lttng
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