linux/tools/perf/Documentation/perf-script-perl.txt
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   1perf-script-perl(1)
   2==================
   3
   4NAME
   5----
   6perf-script-perl - Process trace data with a Perl script
   7
   8SYNOPSIS
   9--------
  10[verse]
  11'perf script' [-s [Perl]:script[.pl] ]
  12
  13DESCRIPTION
  14-----------
  15
  16This perf script option is used to process perf script data using perf's
  17built-in Perl interpreter.  It reads and processes the input file and
  18displays the results of the trace analysis implemented in the given
  19Perl script, if any.
  20
  21STARTER SCRIPTS
  22---------------
  23
  24You 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.
  26That will generate a starter script containing a handler for each of
  27the event types in the trace file; it simply prints every available
  28field for each event in the trace file.
  29
  30You can also look at the existing scripts in
  31~/libexec/perf-core/scripts/perl for typical examples showing how to
  32do basic things like aggregate event data, print results, etc.  Also,
  33the check-perf-script.pl script, while not interesting for its results,
  34attempts to exercise all of the main scripting features.
  35
  36EVENT HANDLERS
  37--------------
  38
  39When 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
  41no handler function defined for a given event type, the event is
  42ignored (or passed to a 'trace_handled' function, see below) and the
  43next event is processed.
  44
  45Most of the event's field values are passed as arguments to the
  46handler function; some of the less common ones aren't - those are
  47available as calls back into the perf executable (see below).
  48
  49As an example, the following perf record command can be used to record
  50all sched_wakeup events in the system:
  51
  52 # perf record -a -e sched:sched_wakeup
  53
  54Traces meant to be processed using a script should be recorded with
  55the above option: -a to enable system-wide collection.
  56
  57The format file for the sched_wakep event defines the following fields
  58(see /sys/kernel/debug/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        field:int common_lock_depth;
  67
  68        field:char comm[TASK_COMM_LEN];
  69        field:pid_t pid;
  70        field:int prio;
  71        field:int success;
  72        field:int target_cpu;
  73----
  74
  75The handler function for this event would be defined as:
  76
  77----
  78sub sched::sched_wakeup
  79{
  80   my ($event_name, $context, $common_cpu, $common_secs,
  81       $common_nsecs, $common_pid, $common_comm,
  82       $comm, $pid, $prio, $success, $target_cpu) = @_;
  83}
  84----
  85
  86The handler function takes the form subsystem::event_name.
  87
  88The $common_* arguments in the handler's argument list are the set of
  89arguments passed to all event handlers; some of the fields correspond
  90to the common_* fields in the format file, but some are synthesized,
  91and some of the common_* fields aren't common enough to to be passed
  92to every event as arguments but are available as library functions.
  93
  94Here's a brief description of each of the invariant event args:
  95
  96 $event_name                the name of the event as text
  97 $context                   an opaque 'cookie' used in calls back into perf
  98 $common_cpu                the cpu the event occurred on
  99 $common_secs               the secs portion of the event timestamp
 100 $common_nsecs              the nsecs portion of the event timestamp
 101 $common_pid                the pid of the current task
 102 $common_comm               the name of the current process
 103
 104All of the remaining fields in the event's format file have
 105counterparts as handler function arguments of the same name, as can be
 106seen in the example above.
 107
 108The above provides the basics needed to directly access every field of
 109every event in a trace, which covers 90% of what you need to know to
 110write a useful trace script.  The sections below cover the rest.
 111
 112SCRIPT LAYOUT
 113-------------
 114
 115Every perf script Perl script should start by setting up a Perl module
 116search path and 'use'ing a few support modules (see module
 117descriptions below):
 118
 119----
 120 use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/perf-script-Util/lib";
 121 use lib "./perf-script-Util/lib";
 122 use Perf::Trace::Core;
 123 use Perf::Trace::Context;
 124 use Perf::Trace::Util;
 125----
 126
 127The rest of the script can contain handler functions and support
 128functions in any order.
 129
 130Aside from the event handler functions discussed above, every script
 131can implement a set of optional functions:
 132
 133*trace_begin*, if defined, is called before any event is processed and
 134gives scripts a chance to do setup tasks:
 135
 136----
 137 sub trace_begin
 138 {
 139 }
 140----
 141
 142*trace_end*, if defined, is called after all events have been
 143 processed and gives scripts a chance to do end-of-script tasks, such
 144 as display results:
 145
 146----
 147sub trace_end
 148{
 149}
 150----
 151
 152*trace_unhandled*, if defined, is called after for any event that
 153 doesn't have a handler explicitly defined for it.  The standard set
 154 of common arguments are passed into it:
 155
 156----
 157sub trace_unhandled
 158{
 159    my ($event_name, $context, $common_cpu, $common_secs,
 160        $common_nsecs, $common_pid, $common_comm) = @_;
 161}
 162----
 163
 164The remaining sections provide descriptions of each of the available
 165built-in perf script Perl modules and their associated functions.
 166
 167AVAILABLE MODULES AND FUNCTIONS
 168-------------------------------
 169
 170The following sections describe the functions and variables available
 171via the various Perf::Trace::* Perl modules.  To use the functions and
 172variables from the given module, add the corresponding 'use
 173Perf::Trace::XXX' line to your perf script script.
 174
 175Perf::Trace::Core Module
 176~~~~~~~~~~~~~~~~~~~~~~~~
 177
 178These functions provide some essential functions to user scripts.
 179
 180The *flag_str* and *symbol_str* functions provide human-readable
 181strings for flag and symbolic fields.  These correspond to the strings
 182and values parsed from the 'print fmt' fields of the event format
 183files:
 184
 185  flag_str($event_name, $field_name, $field_value) - returns the string represention corresponding to $field_value for the flag field $field_name of event $event_name
 186  symbol_str($event_name, $field_name, $field_value) - returns the string represention corresponding to $field_value for the symbolic field $field_name of event $event_name
 187
 188Perf::Trace::Context Module
 189~~~~~~~~~~~~~~~~~~~~~~~~~~~
 190
 191Some of the 'common' fields in the event format file aren't all that
 192common, but need to be made accessible to user scripts nonetheless.
 193
 194Perf::Trace::Context defines a set of functions that can be used to
 195access this data in the context of the current event.  Each of these
 196functions expects a $context variable, which is the same as the
 197$context variable passed into every event handler as the second
 198argument.
 199
 200 common_pc($context) - returns common_preempt count for the current event
 201 common_flags($context) - returns common_flags for the current event
 202 common_lock_depth($context) - returns common_lock_depth for the current event
 203
 204Perf::Trace::Util Module
 205~~~~~~~~~~~~~~~~~~~~~~~~
 206
 207Various utility functions for use with perf script:
 208
 209  nsecs($secs, $nsecs) - returns total nsecs given secs/nsecs pair
 210  nsecs_secs($nsecs) - returns whole secs portion given nsecs
 211  nsecs_nsecs($nsecs) - returns nsecs remainder given nsecs
 212  nsecs_str($nsecs) - returns printable string in the form secs.nsecs
 213  avg($total, $n) - returns average given a sum and a total number of values
 214
 215SEE ALSO
 216--------
 217linkperf:perf-script[1]
 218