1 perf-script-perl(1)
2 ===================
3
4 NAME
5 ----
6 perf-script-perl - Process trace data with a Perl script
7
8 SYNOPSIS
9 --------
10 [verse]
11 'perf script' [-s [Perl]:script[.pl] ]
12
13 DESCRIPTION
14 -----------
15
16 This perf script option is used to process perf script data using perf's
17 built-in Perl interpreter. It reads and processes the input file and
18 displays the results of the trace analysis implemented in the given
19 Perl script, if any.
20
21 STARTER SCRIPTS
22 ---------------
23
24 You can avoid reading the rest of this document by running 'perf script
25 -g perl' in the same directory as an existing perf.data trace file.
26 That will generate a starter script containing a handler for each of
27 the event types in the trace file; it simply prints every available
28 field for each event in the trace file.
29
30 You can also look at the existing scripts in
31 ~/libexec/perf-core/scripts/perl for typical examples showing how to
32 do basic things like aggregate event data, print results, etc. Also,
33 the check-perf-script.pl script, while not interesting for its results,
34 attempts to exercise all of the main scripting features.
35
36 EVENT HANDLERS
37 --------------
38
39 When perf script is invoked using a trace script, a user-defined
40 'handler function' is called for each event in the trace. If there's
41 no handler function defined for a given event type, the event is
42 ignored (or passed to a 'trace_unhandled' function, see below) and the
43 next event is processed.
44
45 Most of the event's field values are passed as arguments to the
46 handler function; some of the less common ones aren't - those are
47 available as calls back into the perf executable (see below).
48
49 As an example, the following perf record command can be used to record
50 all sched_wakeup events in the system:
51
52 # perf record -a -e sched:sched_wakeup
53
54 Traces meant to be processed using a script should be recorded with
55 the above option: -a to enable system-wide collection.
56
57 The format file for the sched_wakeup event defines the following fields
58 (see /sys/kernel/tracing/events/sched/sched_wakeup/format):
59
60 ----
61 format:
62 field:unsigned short common_type;
63 field:unsigned char common_flags;
64 field:unsigned char common_preempt_count;
65 field:int common_pid;
66
67 field:char comm[TASK_COMM_LEN];
68 field:pid_t pid;
69 field:int prio;
70 field:int success;
71 field:int target_cpu;
72 ----
73
74 The handler function for this event would be defined as:
75
76 ----
77 sub sched::sched_wakeup
78 {
79 my ($event_name, $context, $common_cpu, $common_secs,
80 $common_nsecs, $common_pid, $common_comm,
81 $comm, $pid, $prio, $success, $target_cpu) = @_;
82 }
83 ----
84
85 The handler function takes the form subsystem::event_name.
86
87 The $common_* arguments in the handler's argument list are the set of
88 arguments passed to all event handlers; some of the fields correspond
89 to the common_* fields in the format file, but some are synthesized,
90 and some of the common_* fields aren't common enough to to be passed
91 to every event as arguments but are available as library functions.
92
93 Here's a brief description of each of the invariant event args:
94
95 $event_name the name of the event as text
96 $context an opaque 'cookie' used in calls back into perf
97 $common_cpu the cpu the event occurred on
98 $common_secs the secs portion of the event timestamp
99 $common_nsecs the nsecs portion of the event timestamp
100 $common_pid the pid of the current task
101 $common_comm the name of the current process
102
103 All of the remaining fields in the event's format file have
104 counterparts as handler function arguments of the same name, as can be
105 seen in the example above.
106
107 The above provides the basics needed to directly access every field of
108 every event in a trace, which covers 90% of what you need to know to
109 write a useful trace script. The sections below cover the rest.
110
111 SCRIPT LAYOUT
112 -------------
113
114 Every perf script Perl script should start by setting up a Perl module
115 search path and 'use'ing a few support modules (see module
116 descriptions below):
117
118 ----
119 use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
120 use lib "./Perf-Trace-Util/lib";
121 use Perf::Trace::Core;
122 use Perf::Trace::Context;
123 use Perf::Trace::Util;
124 ----
125
126 The rest of the script can contain handler functions and support
127 functions in any order.
128
129 Aside from the event handler functions discussed above, every script
130 can implement a set of optional functions:
131
132 *trace_begin*, if defined, is called before any event is processed and
133 gives scripts a chance to do setup tasks:
134
135 ----
136 sub trace_begin
137 {
138 }
139 ----
140
141 *trace_end*, if defined, is called after all events have been
142 processed and gives scripts a chance to do end-of-script tasks, such
143 as display results:
144
145 ----
146 sub trace_end
147 {
148 }
149 ----
150
151 *trace_unhandled*, if defined, is called after for any event that
152 doesn't have a handler explicitly defined for it. The standard set
153 of common arguments are passed into it:
154
155 ----
156 sub trace_unhandled
157 {
158 my ($event_name, $context, $common_cpu, $common_secs,
159 $common_nsecs, $common_pid, $common_comm) = @_;
160 }
161 ----
162
163 The remaining sections provide descriptions of each of the available
164 built-in perf script Perl modules and their associated functions.
165
166 AVAILABLE MODULES AND FUNCTIONS
167 -------------------------------
168
169 The following sections describe the functions and variables available
170 via the various Perf::Trace::* Perl modules. To use the functions and
171 variables from the given module, add the corresponding 'use
172 Perf::Trace::XXX' line to your perf script script.
173
174 Perf::Trace::Core Module
175 ~~~~~~~~~~~~~~~~~~~~~~~~
176
177 These functions provide some essential functions to user scripts.
178
179 The *flag_str* and *symbol_str* functions provide human-readable
180 strings for flag and symbolic fields. These correspond to the strings
181 and values parsed from the 'print fmt' fields of the event format
182 files:
183
184 flag_str($event_name, $field_name, $field_value) - returns the string representation corresponding to $field_value for the flag field $field_name of event $event_name
185 symbol_str($event_name, $field_name, $field_value) - returns the string representation corresponding to $field_value for the symbolic field $field_name of event $event_name
186
187 Perf::Trace::Context Module
188 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
189
190 Some of the 'common' fields in the event format file aren't all that
191 common, but need to be made accessible to user scripts nonetheless.
192
193 Perf::Trace::Context defines a set of functions that can be used to
194 access this data in the context of the current event. Each of these
195 functions expects a $context variable, which is the same as the
196 $context variable passed into every event handler as the second
197 argument.
198
199 common_pc($context) - returns common_preempt count for the current event
200 common_flags($context) - returns common_flags for the current event
201 common_lock_depth($context) - returns common_lock_depth for the current event
202
203 Perf::Trace::Util Module
204 ~~~~~~~~~~~~~~~~~~~~~~~~
205
206 Various utility functions for use with perf script:
207
208 nsecs($secs, $nsecs) - returns total nsecs given secs/nsecs pair
209 nsecs_secs($nsecs) - returns whole secs portion given nsecs
210 nsecs_nsecs($nsecs) - returns nsecs remainder given nsecs
211 nsecs_str($nsecs) - returns printable string in the form secs.nsecs
212 avg($total, $n) - returns average given a sum and a total number of values
213
214 SEE ALSO
215 --------
216 linkperf:perf-script[1]
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