1PERF-TRACE-PERL(1) perf Manual PERF-TRACE-PERL(1)
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6 perf-trace-perl - Process trace data with a Perl script
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9 perf trace [-s [Perl]:script[.pl] ]
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12 This perf trace option is used to process perf trace data using perf’s
13 built-in Perl interpreter. It reads and processes the input file and
14 displays the results of the trace analysis implemented in the given
15 Perl script, if any.
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18 You can avoid reading the rest of this document by running perf trace
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 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-trace.pl script, while not interesting for its results,
28 attempts to exercise all of the main scripting features.
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31 When perf trace is invoked using a trace script, a user-defined handler
32 function is called for each event in the trace. If there’s no handler
33 function defined for a given event type, the event is ignored (or
34 passed to a trace_handled function, see below) and the next event is
35 processed.
36 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).
40 As an example, the following perf record command can be used to record
42 all sched_wakeup events in the system:
43 # perf record -a -e sched:sched_wakeup
45 Traces meant to be processed using a script should be recorded with the
47 above option: -a to enable system-wide collection.
48 The format file for the sched_wakep event defines the following fields
50 (see /sys/kernel/debug/tracing/events/sched/sched_wakeup/format):
51 .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;
60 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
67 The handler function for this event would be defined as:
70 .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
80 The handler function takes the form subsystem::event_name.
83 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.
89 Here’s a brief description of each of the invariant event args:
91 $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 $common_comm the name of the current process
99 All of the remaining fields in the event’s format file have
101 counterparts as handler function arguments of the same name, as can be
102 seen in the example above.
103 The above provides the basics needed to directly access every field of
105 every event in a trace, which covers 90% of what you need to know to
106 write a useful trace script. The sections below cover the rest.
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109 Every perf trace Perl script should start by setting up a Perl module
110 search path and 'use’ing a few support modules (see module descriptions
111 below):
112 .ft C
115 use lib "$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
121 The rest of the script can contain handler functions and support
124 functions in any order.
125 Aside from the event handler functions discussed above, every script
127 can implement a set of optional functions:
128 trace_begin, if defined, is called before any event is processed and
130 gives scripts a chance to do setup tasks:
131 .ft C
134 sub trace_begin
135 {
136 }
137 .ft
138 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:
143 .ft C
146 sub trace_end
147 {
148 }
149 .ft
150 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:
155 .ft C
158 sub trace_unhandled
159 {
160 my ($event_name, $context, $common_cpu, $common_secs,
161 $common_nsecs, $common_pid, $common_comm) = @_;
162 }
163 .ft
164 The remaining sections provide descriptions of each of the available
167 built-in perf trace Perl modules and their associated functions.
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170 The following sections describe the functions and variables available
171 via the various Perf::Trace::* Perl modules. To use the functions and
172 variables from the given module, add the corresponding use
173 Perf::Trace::XXX line to your perf trace script.
174 Perf::Trace::Core Module
176 These functions provide some essential functions to user scripts.
177 The flag_str and symbol_str functions provide human-readable strings
179 for flag and symbolic fields. These correspond to the strings and
180 values parsed from the print fmt fields of the event format files:
181 flag_str($event_name, $field_name, $field_value) - returns the string represention 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 represention corresponding to $field_value for the symbolic field $field_name of event $event_name
184 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 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 $context variable passed into every event handler as the second
193 argument.
194 common_pc($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 Perf::Trace::Util Module
200 Various utility functions for use with perf trace:
201 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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209 perf-trace(1)
210perf 2.6.35.14-106.fc 11/23/2011 PERF-TRACE-PERL(1)