perf-script-perl(1)
  ==================
  
  NAME
  ----
  perf-script-perl - Process trace data with a Perl script
  
  SYNOPSIS
  --------
  [verse]
  'perf script' [-s [Perl]:script[.pl] ]
  
  DESCRIPTION
  -----------
  
  This perf script option is used to process perf script data using perf's
  built-in Perl interpreter.  It reads and processes the input file and
  displays the results of the trace analysis implemented in the given
  Perl script, if any.
  
  STARTER SCRIPTS
  ---------------
  
  You can avoid reading the rest of this document by running 'perf script
  -g perl' in the same directory as an existing perf.data trace file.
  That will generate a starter script containing a handler for each of
  the event types in the trace file; it simply prints every available
  field for each event in the trace file.
  
  You can also look at the existing scripts in
  ~/libexec/perf-core/scripts/perl for typical examples showing how to
  do basic things like aggregate event data, print results, etc.  Also,
  the check-perf-script.pl script, while not interesting for its results,
  attempts to exercise all of the main scripting features.
  
  EVENT HANDLERS
  --------------
  
  When perf script is invoked using a trace script, a user-defined
  'handler function' is called for each event in the trace.  If there's
  no handler function defined for a given event type, the event is
  ignored (or passed to a 'trace_handled' function, see below) and the
  next event is processed.
  
  Most of the event's field values are passed as arguments to the
  handler function; some of the less common ones aren't - those are
  available as calls back into the perf executable (see below).
  
  As an example, the following perf record command can be used to record
  all sched_wakeup events in the system:
  
   # perf record -a -e sched:sched_wakeup
  
  Traces meant to be processed using a script should be recorded with
  the above option: -a to enable system-wide collection.
  
  The format file for the sched_wakep event defines the following fields
  (see /sys/kernel/debug/tracing/events/sched/sched_wakeup/format):
  
  ----
   format:
          field:unsigned short common_type;
          field:unsigned char common_flags;
          field:unsigned char common_preempt_count;
          field:int common_pid;
  
          field:char comm[TASK_COMM_LEN];
          field:pid_t pid;
          field:int prio;
          field:int success;
          field:int target_cpu;
  ----
  
  The handler function for this event would be defined as:
  
  ----
  sub sched::sched_wakeup
  {
     my ($event_name, $context, $common_cpu, $common_secs,
         $common_nsecs, $common_pid, $common_comm,
         $comm, $pid, $prio, $success, $target_cpu) = @_;
  }
  ----
  
  The handler function takes the form subsystem::event_name.
  
  The $common_* arguments in the handler's argument list are the set of
  arguments passed to all event handlers; some of the fields correspond
  to the common_* fields in the format file, but some are synthesized,
  and some of the common_* fields aren't common enough to to be passed
  to every event as arguments but are available as library functions.
  
  Here's a brief description of each of the invariant event args:
  
   $event_name 	  	    the name of the event as text
   $context		    an opaque 'cookie' used in calls back into perf
   $common_cpu		    the cpu the event occurred on
   $common_secs		    the secs portion of the event timestamp
   $common_nsecs		    the nsecs portion of the event timestamp
   $common_pid		    the pid of the current task
   $common_comm		    the name of the current process
  
  All of the remaining fields in the event's format file have
  counterparts as handler function arguments of the same name, as can be
  seen in the example above.
  
  The above provides the basics needed to directly access every field of
  every event in a trace, which covers 90% of what you need to know to
  write a useful trace script.  The sections below cover the rest.
  
  SCRIPT LAYOUT
  -------------
  
  Every perf script Perl script should start by setting up a Perl module
  search path and 'use'ing a few support modules (see module
  descriptions below):
  
  ----
   use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
   use lib "./Perf-Trace-Util/lib";
   use Perf::Trace::Core;
   use Perf::Trace::Context;
   use Perf::Trace::Util;
  ----
  
  The rest of the script can contain handler functions and support
  functions in any order.
  
  Aside from the event handler functions discussed above, every script
  can implement a set of optional functions:
  
  *trace_begin*, if defined, is called before any event is processed and
  gives scripts a chance to do setup tasks:
  
  ----
   sub trace_begin
   {
   }
  ----
  
  *trace_end*, if defined, is called after all events have been
   processed and gives scripts a chance to do end-of-script tasks, such
   as display results:
  
  ----
  sub trace_end
  {
  }
  ----
  
  *trace_unhandled*, if defined, is called after for any event that
   doesn't have a handler explicitly defined for it.  The standard set
   of common arguments are passed into it:
  
  ----
  sub trace_unhandled
  {
      my ($event_name, $context, $common_cpu, $common_secs,
          $common_nsecs, $common_pid, $common_comm) = @_;
  }
  ----
  
  The remaining sections provide descriptions of each of the available
  built-in perf script Perl modules and their associated functions.
  
  AVAILABLE MODULES AND FUNCTIONS
  -------------------------------
  
  The following sections describe the functions and variables available
  via the various Perf::Trace::* Perl modules.  To use the functions and
  variables from the given module, add the corresponding 'use
  Perf::Trace::XXX' line to your perf script script.
  
  Perf::Trace::Core Module
  ~~~~~~~~~~~~~~~~~~~~~~~~
  
  These functions provide some essential functions to user scripts.
  
  The *flag_str* and *symbol_str* functions provide human-readable
  strings for flag and symbolic fields.  These correspond to the strings
  and values parsed from the 'print fmt' fields of the event format
  files:
  
    flag_str($event_name, $field_name, $field_value) - returns the string represention corresponding to $field_value for the flag field $field_name of event $event_name
    symbol_str($event_name, $field_name, $field_value) - returns the string represention corresponding to $field_value for the symbolic field $field_name of event $event_name
  
  Perf::Trace::Context Module
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  Some of the 'common' fields in the event format file aren't all that
  common, but need to be made accessible to user scripts nonetheless.
  
  Perf::Trace::Context defines a set of functions that can be used to
  access this data in the context of the current event.  Each of these
  functions expects a $context variable, which is the same as the
  $context variable passed into every event handler as the second
  argument.
  
   common_pc($context) - returns common_preempt count for the current event
   common_flags($context) - returns common_flags for the current event
   common_lock_depth($context) - returns common_lock_depth for the current event
  
  Perf::Trace::Util Module
  ~~~~~~~~~~~~~~~~~~~~~~~~
  
  Various utility functions for use with perf script:
  
    nsecs($secs, $nsecs) - returns total nsecs given secs/nsecs pair
    nsecs_secs($nsecs) - returns whole secs portion given nsecs
    nsecs_nsecs($nsecs) - returns nsecs remainder given nsecs
    nsecs_str($nsecs) - returns printable string in the form secs.nsecs
    avg($total, $n) - returns average given a sum and a total number of values
  
  SEE ALSO
  --------
  linkperf:perf-script[1]