perf-script-perl.txt 7.2 KB

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  1. perf-script-perl(1)
  2. ===================
  3. NAME
  4. ----
  5. perf-script-perl - Process trace data with a Perl script
  6. SYNOPSIS
  7. --------
  8. [verse]
  9. 'perf script' [-s [Perl]:script[.pl] ]
  10. DESCRIPTION
  11. -----------
  12. This perf script option is used to process perf script 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.
  16. STARTER SCRIPTS
  17. ---------------
  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.
  20. That will generate a starter script containing a handler for each of
  21. the event types in the trace file; it simply prints every available
  22. field for each event in the trace file.
  23. You can also look at the existing scripts in
  24. ~/libexec/perf-core/scripts/perl for typical examples showing how to
  25. do basic things like aggregate event data, print results, etc. Also,
  26. the check-perf-script.pl script, while not interesting for its results,
  27. attempts to exercise all of the main scripting features.
  28. EVENT HANDLERS
  29. --------------
  30. When perf script is invoked using a trace script, a user-defined
  31. 'handler function' is called for each event in the trace. If there's
  32. no handler function defined for a given event type, the event is
  33. ignored (or passed to a 'trace_unhandled' function, see below) and the
  34. next event is processed.
  35. Most of the event's field values are passed as arguments to the
  36. handler function; some of the less common ones aren't - those are
  37. available as calls back into the perf executable (see below).
  38. As an example, the following perf record command can be used to record
  39. all sched_wakeup events in the system:
  40. # perf record -a -e sched:sched_wakeup
  41. Traces meant to be processed using a script should be recorded with
  42. the above option: -a to enable system-wide collection.
  43. The format file for the sched_wakep event defines the following fields
  44. (see /sys/kernel/debug/tracing/events/sched/sched_wakeup/format):
  45. ----
  46. format:
  47. field:unsigned short common_type;
  48. field:unsigned char common_flags;
  49. field:unsigned char common_preempt_count;
  50. field:int common_pid;
  51. field:char comm[TASK_COMM_LEN];
  52. field:pid_t pid;
  53. field:int prio;
  54. field:int success;
  55. field:int target_cpu;
  56. ----
  57. The handler function for this event would be defined as:
  58. ----
  59. sub sched::sched_wakeup
  60. {
  61. my ($event_name, $context, $common_cpu, $common_secs,
  62. $common_nsecs, $common_pid, $common_comm,
  63. $comm, $pid, $prio, $success, $target_cpu) = @_;
  64. }
  65. ----
  66. The handler function takes the form subsystem::event_name.
  67. The $common_* arguments in the handler's argument list are the set of
  68. arguments passed to all event handlers; some of the fields correspond
  69. to the common_* fields in the format file, but some are synthesized,
  70. and some of the common_* fields aren't common enough to to be passed
  71. to every event as arguments but are available as library functions.
  72. Here's a brief description of each of the invariant event args:
  73. $event_name the name of the event as text
  74. $context an opaque 'cookie' used in calls back into perf
  75. $common_cpu the cpu the event occurred on
  76. $common_secs the secs portion of the event timestamp
  77. $common_nsecs the nsecs portion of the event timestamp
  78. $common_pid the pid of the current task
  79. $common_comm the name of the current process
  80. All of the remaining fields in the event's format file have
  81. counterparts as handler function arguments of the same name, as can be
  82. seen in the example above.
  83. The above provides the basics needed to directly access every field of
  84. every event in a trace, which covers 90% of what you need to know to
  85. write a useful trace script. The sections below cover the rest.
  86. SCRIPT LAYOUT
  87. -------------
  88. Every perf script Perl script should start by setting up a Perl module
  89. search path and 'use'ing a few support modules (see module
  90. descriptions below):
  91. ----
  92. use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
  93. use lib "./Perf-Trace-Util/lib";
  94. use Perf::Trace::Core;
  95. use Perf::Trace::Context;
  96. use Perf::Trace::Util;
  97. ----
  98. The rest of the script can contain handler functions and support
  99. functions in any order.
  100. Aside from the event handler functions discussed above, every script
  101. can implement a set of optional functions:
  102. *trace_begin*, if defined, is called before any event is processed and
  103. gives scripts a chance to do setup tasks:
  104. ----
  105. sub trace_begin
  106. {
  107. }
  108. ----
  109. *trace_end*, if defined, is called after all events have been
  110. processed and gives scripts a chance to do end-of-script tasks, such
  111. as display results:
  112. ----
  113. sub trace_end
  114. {
  115. }
  116. ----
  117. *trace_unhandled*, if defined, is called after for any event that
  118. doesn't have a handler explicitly defined for it. The standard set
  119. of common arguments are passed into it:
  120. ----
  121. sub trace_unhandled
  122. {
  123. my ($event_name, $context, $common_cpu, $common_secs,
  124. $common_nsecs, $common_pid, $common_comm) = @_;
  125. }
  126. ----
  127. The remaining sections provide descriptions of each of the available
  128. built-in perf script Perl modules and their associated functions.
  129. AVAILABLE MODULES AND FUNCTIONS
  130. -------------------------------
  131. The following sections describe the functions and variables available
  132. via the various Perf::Trace::* Perl modules. To use the functions and
  133. variables from the given module, add the corresponding 'use
  134. Perf::Trace::XXX' line to your perf script script.
  135. Perf::Trace::Core Module
  136. ~~~~~~~~~~~~~~~~~~~~~~~~
  137. These functions provide some essential functions to user scripts.
  138. The *flag_str* and *symbol_str* functions provide human-readable
  139. strings for flag and symbolic fields. These correspond to the strings
  140. and values parsed from the 'print fmt' fields of the event format
  141. files:
  142. flag_str($event_name, $field_name, $field_value) - returns the string representation corresponding to $field_value for the flag field $field_name of event $event_name
  143. symbol_str($event_name, $field_name, $field_value) - returns the string representation corresponding to $field_value for the symbolic field $field_name of event $event_name
  144. Perf::Trace::Context Module
  145. ~~~~~~~~~~~~~~~~~~~~~~~~~~~
  146. Some of the 'common' fields in the event format file aren't all that
  147. common, but need to be made accessible to user scripts nonetheless.
  148. Perf::Trace::Context defines a set of functions that can be used to
  149. access this data in the context of the current event. Each of these
  150. functions expects a $context variable, which is the same as the
  151. $context variable passed into every event handler as the second
  152. argument.
  153. common_pc($context) - returns common_preempt count for the current event
  154. common_flags($context) - returns common_flags for the current event
  155. common_lock_depth($context) - returns common_lock_depth for the current event
  156. Perf::Trace::Util Module
  157. ~~~~~~~~~~~~~~~~~~~~~~~~
  158. Various utility functions for use with perf script:
  159. nsecs($secs, $nsecs) - returns total nsecs given secs/nsecs pair
  160. nsecs_secs($nsecs) - returns whole secs portion given nsecs
  161. nsecs_nsecs($nsecs) - returns nsecs remainder given nsecs
  162. nsecs_str($nsecs) - returns printable string in the form secs.nsecs
  163. avg($total, $n) - returns average given a sum and a total number of values
  164. SEE ALSO
  165. --------
  166. linkperf:perf-script[1]