1PERF-SCRIPT-PERL(1)               perf Manual              PERF-SCRIPT-PERL(1)
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NAME

6       perf-script-perl - Process trace data with a Perl script
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SYNOPSIS

9       perf script [-s [Perl]:script[.pl] ]
10

DESCRIPTION

12       This perf script option is used to process perf script data using
13       perf’s built-in Perl interpreter. It reads and processes the input file
14       and displays the results of the trace analysis implemented in the given
15       Perl script, if any.
16

STARTER SCRIPTS

18       You can avoid reading the rest of this document by running perf script
19       -g perl in the same directory as an existing perf.data trace file. That
20       will generate a starter script containing a handler for each of the
21       event types in the trace file; it simply prints every available field
22       for each event in the trace file.
23
24       You can also look at the existing scripts in
25       ~/libexec/perf-core/scripts/perl for typical examples showing how to do
26       basic things like aggregate event data, print results, etc. Also, the
27       check-perf-script.pl script, while not interesting for its results,
28       attempts to exercise all of the main scripting features.
29

EVENT HANDLERS

31       When perf script is invoked using a trace script, a user-defined
32       handler function is called for each event in the trace. If there’s no
33       handler function defined for a given event type, the event is ignored
34       (or passed to a trace_unhandled function, see below) and the next event
35       is processed.
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37       Most of the event’s field values are passed as arguments to the handler
38       function; some of the less common ones aren’t - those are available as
39       calls back into the perf executable (see below).
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41       As an example, the following perf record command can be used to record
42       all sched_wakeup events in the system:
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44           # perf record -a -e sched:sched_wakeup
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46       Traces meant to be processed using a script should be recorded with the
47       above option: -a to enable system-wide collection.
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49       The format file for the sched_wakeup event defines the following fields
50       (see /sys/kernel/debug/tracing/events/sched/sched_wakeup/format):
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52
53           .ft C
54            format:
55                   field:unsigned short common_type;
56                   field:unsigned char common_flags;
57                   field:unsigned char common_preempt_count;
58                   field:int common_pid;
59
60                   field:char comm[TASK_COMM_LEN];
61                   field:pid_t pid;
62                   field:int prio;
63                   field:int success;
64                   field:int target_cpu;
65           .ft
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67
68       The handler function for this event would be defined as:
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70
71           .ft C
72           sub sched::sched_wakeup
73           {
74              my ($event_name, $context, $common_cpu, $common_secs,
75                  $common_nsecs, $common_pid, $common_comm,
76                  $comm, $pid, $prio, $success, $target_cpu) = @_;
77           }
78           .ft
79
80
81       The handler function takes the form subsystem::event_name.
82
83       The $common_* arguments in the handler’s argument list are the set of
84       arguments passed to all event handlers; some of the fields correspond
85       to the common_* fields in the format file, but some are synthesized,
86       and some of the common_* fields aren’t common enough to to be passed to
87       every event as arguments but are available as library functions.
88
89       Here’s a brief description of each of the invariant event args:
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91           $event_name                the name of the event as text
92           $context                   an opaque 'cookie' used in calls back into perf
93           $common_cpu                the cpu the event occurred on
94           $common_secs               the secs portion of the event timestamp
95           $common_nsecs              the nsecs portion of the event timestamp
96           $common_pid                the pid of the current task
97           $common_comm               the name of the current process
98
99       All of the remaining fields in the event’s format file have
100       counterparts as handler function arguments of the same name, as can be
101       seen in the example above.
102
103       The above provides the basics needed to directly access every field of
104       every event in a trace, which covers 90% of what you need to know to
105       write a useful trace script. The sections below cover the rest.
106

SCRIPT LAYOUT

108       Every perf script Perl script should start by setting up a Perl module
109       search path and 'use’ing a few support modules (see module descriptions
110       below):
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112
113           .ft C
114            use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
115            use lib "./Perf-Trace-Util/lib";
116            use Perf::Trace::Core;
117            use Perf::Trace::Context;
118            use Perf::Trace::Util;
119           .ft
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121
122       The rest of the script can contain handler functions and support
123       functions in any order.
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125       Aside from the event handler functions discussed above, every script
126       can implement a set of optional functions:
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128       trace_begin, if defined, is called before any event is processed and
129       gives scripts a chance to do setup tasks:
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131
132           .ft C
133            sub trace_begin
134            {
135            }
136           .ft
137
138
139       trace_end, if defined, is called after all events have been processed
140       and gives scripts a chance to do end-of-script tasks, such as display
141       results:
142
143
144           .ft C
145           sub trace_end
146           {
147           }
148           .ft
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150
151       trace_unhandled, if defined, is called after for any event that doesn’t
152       have a handler explicitly defined for it. The standard set of common
153       arguments are passed into it:
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155
156           .ft C
157           sub trace_unhandled
158           {
159               my ($event_name, $context, $common_cpu, $common_secs,
160                   $common_nsecs, $common_pid, $common_comm) = @_;
161           }
162           .ft
163
164
165       The remaining sections provide descriptions of each of the available
166       built-in perf script Perl modules and their associated functions.
167

AVAILABLE MODULES AND FUNCTIONS

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.
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174   Perf::Trace::Core Module
175       These functions provide some essential functions to user scripts.
176
177       The flag_str and symbol_str functions provide human-readable strings
178       for flag and symbolic fields. These correspond to the strings and
179       values parsed from the print fmt fields of the event format files:
180
181           flag_str($event_name, $field_name, $field_value) - returns the string representation corresponding to $field_value for the flag field $field_name of event $event_name
182           symbol_str($event_name, $field_name, $field_value) - returns the string representation corresponding to $field_value for the symbolic field $field_name of event $event_name
183
184   Perf::Trace::Context Module
185       Some of the common fields in the event format file aren’t all that
186       common, but need to be made accessible to user scripts nonetheless.
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188       Perf::Trace::Context defines a set of functions that can be used to
189       access this data in the context of the current event. Each of these
190       functions expects a $context variable, which is the same as the
191       $context variable passed into every event handler as the second
192       argument.
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194           common_pc($context) - returns common_preempt count for the current event
195           common_flags($context) - returns common_flags for the current event
196           common_lock_depth($context) - returns common_lock_depth for the current event
197
198   Perf::Trace::Util Module
199       Various utility functions for use with perf script:
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201           nsecs($secs, $nsecs) - returns total nsecs given secs/nsecs pair
202           nsecs_secs($nsecs) - returns whole secs portion given nsecs
203           nsecs_nsecs($nsecs) - returns nsecs remainder given nsecs
204           nsecs_str($nsecs) - returns printable string in the form secs.nsecs
205           avg($total, $n) - returns average given a sum and a total number of values
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SEE ALSO

208       perf-script(1)
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212perf                              06/14/2022               PERF-SCRIPT-PERL(1)
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