NAME
perf-probe - Define new dynamic tracepoints
SYNOPSIS
perf probe [options] --add=PROBE [...]
or
perf probe [options] PROBE
or
perf probe [options] --del=[GROUP:]EVENT [...]
or
perf probe --list
or
perf probe --line=FUNC[:RLN[+NUM|:RLN2]]|SRC:ALN[+NUM|:ALN2]
DESCRIPTION
This command defines dynamic tracepoint events, by symbol and registers
without debuginfo, or by C expressions (C line numbers, C function
names, and C local variables) with debuginfo.
OPTIONS
-k, --vmlinux=PATH
Specify vmlinux path which has debuginfo (Dwarf binary).
-s, --source=PATH
Specify path to kernel source.
-v, --verbose
Be more verbose (show parsed arguments, etc).
-a, --add=
Define a probe event (see PROBE SYNTAX for detail).
-d, --del=
Delete probe events. This accepts glob wildcards(*, ?) and
character classes(e.g. [a-z], [!A-Z]).
-l, --list
List up current probe events.
-L, --line=
Show source code lines which can be probed. This needs an argument
which specifies a range of the source code. (see LINE SYNTAX for
detail)
-f, --force
Forcibly add events with existing name.
-n, --dry-run
Dry run. With this option, --add and --del doesn't execute actual
adding and removal operations.
--max-probes
Set the maximum number of probe points for an event. Default is
128.
PROBE SYNTAX
Probe points are defined by following syntax.
1) Define event based on function name
[EVENT=]FUNC[@SRC][:RLN|+OFFS|%return|;PTN] [ARG ...]
2) Define event based on source file with line number
[EVENT=]SRC:ALN [ARG ...]
3) Define event based on source file with lazy pattern
[EVENT=]SRC;PTN [ARG ...]
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. 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. It 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. ARG specifies the arguments of this
probe point, (see PROBE ARGUMENT).
PROBE ARGUMENT
Each probe argument follows below syntax.
[NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
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.) TYPE casts the type of this argument
(optional). If omitted, perf probe automatically set the type based on
debuginfo.
LINE SYNTAX
Line range is descripted by following syntax.
"FUNC[:RLN[+NUM|-RLN2]]|SRC:ALN[+NUM|-ALN2]"
FUNC specifies the function name of showing lines. RLN is the start
line number from function entry line, and RLN2 is the end line number.
As same as probe syntax, SRC means the source file path, ALN is start
line number, and ALN2 is end line number in the file. It is also
possible to specify how many lines to show by using NUM. So,
"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.
LAZY MATCHING
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]).
e.g. a=* can matches a=b, a = b, a == b and so on.
This 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.)
EXAMPLES
Display which lines in schedule() can be probed:
./perf probe --line schedule
Add a probe on schedule() function 12th line with recording cpu local
variable:
./perf probe schedule:12 cpu
or
./perf probe --add='schedule:12 cpu'
this will add one or more probes which has the name start with "schedule".
Add probes on lines in schedule() function which calls update_rq_clock().
./perf probe 'schedule;update_rq_clock*'
or
./perf probe --add='schedule;update_rq_clock*'
Delete all probes on schedule().
./perf probe --del='schedule*'
SEE ALSO
perf-trace(1), perf-record(1)