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.
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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.
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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_handled 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_wakep 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                   field:int common_lock_depth;
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61                   field:char comm[TASK_COMM_LEN];
62                   field:pid_t pid;
63                   field:int prio;
64                   field:int success;
65                   field:int target_cpu;
66           .ft
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68
69       The handler function for this event would be defined as:
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71
72           .ft C
73           sub sched::sched_wakeup
74           {
75              my ($event_name, $context, $common_cpu, $common_secs,
76                  $common_nsecs, $common_pid, $common_comm,
77                  $comm, $pid, $prio, $success, $target_cpu) = @_;
78           }
79           .ft
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81
82       The handler function takes the form subsystem::event_name.
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84       The $common_* arguments in the handler’s argument list are the set of
85       arguments passed to all event handlers; some of the fields correspond
86       to the common_* fields in the format file, but some are synthesized,
87       and some of the common_* fields aren’t common enough to to be passed to
88       every event as arguments but are available as library functions.
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90       Here’s a brief description of each of the invariant event args:
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92           $event_name                the name of the event as text
93           $context                   an opaque ´cookie´ used in calls back into perf
94           $common_cpu                the cpu the event occurred on
95           $common_secs               the secs portion of the event timestamp
96           $common_nsecs              the nsecs portion of the event timestamp
97           $common_pid                the pid of the current task
98           $common_comm               the name of the current process
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100       All of the remaining fields in the event’s format file have
101       counterparts as handler function arguments of the same name, as can be
102       seen in the example above.
103
104       The above provides the basics needed to directly access every field of
105       every event in a trace, which covers 90% of what you need to know to
106       write a useful trace script. The sections below cover the rest.
107

SCRIPT LAYOUT

109       Every perf script Perl script should start by setting up a Perl module
110       search path and ´use’ing a few support modules (see module descriptions
111       below):
112
113
114           .ft C
115            use lib "$ENV{´PERF_EXEC_PATH´}/scripts/perl/Perf-Trace-Util/lib";
116            use lib "./Perf-Trace-Util/lib";
117            use Perf::Trace::Core;
118            use Perf::Trace::Context;
119            use Perf::Trace::Util;
120           .ft
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122
123       The rest of the script can contain handler functions and support
124       functions in any order.
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126       Aside from the event handler functions discussed above, every script
127       can implement a set of optional functions:
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129       trace_begin, if defined, is called before any event is processed and
130       gives scripts a chance to do setup tasks:
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132
133           .ft C
134            sub trace_begin
135            {
136            }
137           .ft
138
139
140       trace_end, if defined, is called after all events have been processed
141       and gives scripts a chance to do end-of-script tasks, such as display
142       results:
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144
145           .ft C
146           sub trace_end
147           {
148           }
149           .ft
150
151
152       trace_unhandled, if defined, is called after for any event that doesn’t
153       have a handler explicitly defined for it. The standard set of common
154       arguments are passed into it:
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156
157           .ft C
158           sub trace_unhandled
159           {
160               my ($event_name, $context, $common_cpu, $common_secs,
161                   $common_nsecs, $common_pid, $common_comm) = @_;
162           }
163           .ft
164
165
166       The remaining sections provide descriptions of each of the available
167       built-in perf script Perl modules and their associated functions.
168

AVAILABLE MODULES AND FUNCTIONS

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

209       perf-script(1)
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213perf                              06/18/2019               PERF-SCRIPT-PERL(1)
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