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