Root/tools/perf/Documentation/perf-probe.txt

Source at commit ec7cab4cbb721bff91ec924ec691efd8daf36579 created 12 years 8 months ago.
By Maarten ter Huurne, MIPS: JZ4740: A320: Updated quickstart documentation.
1perf-probe(1)
2=============
3
4NAME
5----
6perf-probe - Define new dynamic tracepoints
7
8SYNOPSIS
9--------
10[verse]
11'perf probe' [options] --add='PROBE' [...]
12or
13'perf probe' [options] PROBE
14or
15'perf probe' [options] --del='[GROUP:]EVENT' [...]
16or
17'perf probe' --list
18or
19'perf probe' [options] --line='LINE'
20or
21'perf probe' [options] --vars='PROBEPOINT'
22
23DESCRIPTION
24-----------
25This command defines dynamic tracepoint events, by symbol and registers
26without debuginfo, or by C expressions (C line numbers, C function names,
27and C local variables) with debuginfo.
28
29
30OPTIONS
31-------
32-k::
33--vmlinux=PATH::
34    Specify vmlinux path which has debuginfo (Dwarf binary).
35
36-m::
37--module=MODNAME::
38    Specify module name in which perf-probe searches probe points
39    or lines.
40
41-s::
42--source=PATH::
43    Specify path to kernel source.
44
45-v::
46--verbose::
47        Be more verbose (show parsed arguments, etc).
48
49-a::
50--add=::
51    Define a probe event (see PROBE SYNTAX for detail).
52
53-d::
54--del=::
55    Delete probe events. This accepts glob wildcards('*', '?') and character
56    classes(e.g. [a-z], [!A-Z]).
57
58-l::
59--list::
60    List up current probe events.
61
62-L::
63--line=::
64    Show source code lines which can be probed. This needs an argument
65    which specifies a range of the source code. (see LINE SYNTAX for detail)
66
67-V::
68--vars=::
69    Show available local variables at given probe point. The argument
70    syntax is same as PROBE SYNTAX, but NO ARGs.
71
72--externs::
73    (Only for --vars) Show external defined variables in addition to local
74    variables.
75
76-F::
77--funcs::
78    Show available functions in given module or kernel.
79
80--filter=FILTER::
81    (Only for --vars and --funcs) Set filter. FILTER is a combination of glob
82    pattern, see FILTER PATTERN for detail.
83    Default FILTER is "!__k???tab_* & !__crc_*" for --vars, and "!_*"
84    for --funcs.
85    If several filters are specified, only the last filter is used.
86
87-f::
88--force::
89    Forcibly add events with existing name.
90
91-n::
92--dry-run::
93    Dry run. With this option, --add and --del doesn't execute actual
94    adding and removal operations.
95
96--max-probes::
97    Set the maximum number of probe points for an event. Default is 128.
98
99PROBE SYNTAX
100------------
101Probe points are defined by following syntax.
102
103    1) Define event based on function name
104     [EVENT=]FUNC[@SRC][:RLN|+OFFS|%return|;PTN] [ARG ...]
105
106    2) Define event based on source file with line number
107     [EVENT=]SRC:ALN [ARG ...]
108
109    3) Define event based on source file with lazy pattern
110     [EVENT=]SRC;PTN [ARG ...]
111
112
113'EVENT' specifies the name of new event, if omitted, it will be set the name of the probed function. Currently, event group name is set as 'probe'.
114'FUNC' specifies a probed function name, and it may have one of the following options; '+OFFS' is the offset from function entry address in bytes, ':RLN' is the relative-line number from function entry line, and '%return' means that it probes function return. And ';PTN' means lazy matching pattern (see LAZY MATCHING). Note that ';PTN' must be the end of the probe point definition. In addition, '@SRC' specifies a source file which has that function.
115It is also possible to specify a probe point by the source line number or lazy matching by using 'SRC:ALN' or 'SRC;PTN' syntax, where 'SRC' is the source file path, ':ALN' is the line number and ';PTN' is the lazy matching pattern.
116'ARG' specifies the arguments of this probe point, (see PROBE ARGUMENT).
117
118PROBE ARGUMENT
119--------------
120Each probe argument follows below syntax.
121
122 [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
123
124'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), local array with fixed index (e.g. array[1], var->array[0], var->pointer[2]), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
125'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo. You can specify 'string' type only for the local variable or structure member which is an array of or a pointer to 'char' or 'unsigned char' type.
126
127LINE SYNTAX
128-----------
129Line range is described by following syntax.
130
131 "FUNC[@SRC][:RLN[+NUM|-RLN2]]|SRC[:ALN[+NUM|-ALN2]]"
132
133FUNC specifies the function name of showing lines. 'RLN' is the start line
134number from function entry line, and 'RLN2' is the end line number. As same as
135probe syntax, 'SRC' means the source file path, 'ALN' is start line number,
136and 'ALN2' is end line number in the file. It is also possible to specify how
137many lines to show by using 'NUM'. Moreover, 'FUNC@SRC' combination is good
138for searching a specific function when several functions share same name.
139So, "source.c:100-120" shows lines between 100th to l20th in source.c file. And "func:10+20" shows 20 lines from 10th line of func function.
140
141LAZY MATCHING
142-------------
143 The lazy line matching is similar to glob matching but ignoring spaces in both of pattern and target. So this accepts wildcards('*', '?') and character classes(e.g. [a-z], [!A-Z]).
144
145e.g.
146 'a=*' can matches 'a=b', 'a = b', 'a == b' and so on.
147
148This provides some sort of flexibility and robustness to probe point definitions against minor code changes. For example, actual 10th line of schedule() can be moved easily by modifying schedule(), but the same line matching 'rq=cpu_rq*' may still exist in the function.)
149
150FILTER PATTERN
151--------------
152 The filter pattern is a glob matching pattern(s) to filter variables.
153 In addition, you can use "!" for specifying filter-out rule. You also can give several rules combined with "&" or "|", and fold those rules as one rule by using "(" ")".
154
155e.g.
156 With --filter "foo* | bar*", perf probe -V shows variables which start with "foo" or "bar".
157 With --filter "!foo* & *bar", perf probe -V shows variables which don't start with "foo" and end with "bar", like "fizzbar". But "foobar" is filtered out.
158
159EXAMPLES
160--------
161Display which lines in schedule() can be probed:
162
163 ./perf probe --line schedule
164
165Add a probe on schedule() function 12th line with recording cpu local variable:
166
167 ./perf probe schedule:12 cpu
168 or
169 ./perf probe --add='schedule:12 cpu'
170
171 this will add one or more probes which has the name start with "schedule".
172
173 Add probes on lines in schedule() function which calls update_rq_clock().
174
175 ./perf probe 'schedule;update_rq_clock*'
176 or
177 ./perf probe --add='schedule;update_rq_clock*'
178
179Delete all probes on schedule().
180
181 ./perf probe --del='schedule*'
182
183
184SEE ALSO
185--------
186linkperf:perf-trace[1], linkperf:perf-record[1]
187

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