1perf-trace-perl(1) 2================== 3 4NAME 5---- 6perf-trace-perl - Process trace data with a Perl script 7 8SYNOPSIS 9-------- 10[verse] 11'perf trace' [-s [Perl]:script[.pl] ] 12 13DESCRIPTION 14----------- 15 16This perf trace option is used to process perf trace 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 trace 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-trace.pl script, while not interesting for its results, 34attempts to exercise all of the main scripting features. 35 36EVENT HANDLERS 37-------------- 38 39When perf trace 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 $common_comm the name of the current process 103 104All of the remaining fields in the event's format file have 105counterparts as handler function arguments of the same name, as can be 106seen in the example above. 107 108The above provides the basics needed to directly access every field of 109every event in a trace, which covers 90% of what you need to know to 110write a useful trace script. The sections below cover the rest. 111 112SCRIPT LAYOUT 113------------- 114 115Every perf trace Perl script should start by setting up a Perl module 116search path and 'use'ing a few support modules (see module 117descriptions below): 118 119---- 120 use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib"; 121 use lib "./Perf-Trace-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, $common_comm) = @_; 161} 162---- 163 164The remaining sections provide descriptions of each of the available 165built-in perf trace Perl modules and their associated functions. 166 167AVAILABLE MODULES AND FUNCTIONS 168------------------------------- 169 170The following sections describe the functions and variables available 171via the various Perf::Trace::* Perl modules. To use the functions and 172variables from the given module, add the corresponding 'use 173Perf::Trace::XXX' line to your perf trace script. 174 175Perf::Trace::Core Module 176~~~~~~~~~~~~~~~~~~~~~~~~ 177 178These functions provide some essential functions to user scripts. 179 180The *flag_str* and *symbol_str* functions provide human-readable 181strings for flag and symbolic fields. These correspond to the strings 182and values parsed from the 'print fmt' fields of the event format 183files: 184 185 flag_str($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($context) - returns common_lock_depth for the current event 203 204Perf::Trace::Util Module 205~~~~~~~~~~~~~~~~~~~~~~~~ 206 207Various utility functions for use with perf trace: 208 209 nsecs($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-trace[1] 218