perf-script-perl(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | STARTER SCRIPTS | EVENT HANDLERS | SCRIPT LAYOUT | AVAILABLE MODULES AND FUNCTIONS | SEE ALSO | COLOPHON

PERF-SCRIPT-PERL(1)            perf Manual           PERF-SCRIPT-PERL(1)

NAME         top

       perf-script-perl - Process trace data with a Perl script

SYNOPSIS         top

       perf script [-s [Perl]:script[.pl] ]

DESCRIPTION         top

       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         top

       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         top

       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_unhandled 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):

           .ft C
            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;
           .ft

       The handler function for this event would be defined as:

           .ft C
           sub sched::sched_wakeup
           {
              my ($event_name, $context, $common_cpu, $common_secs,
                  $common_nsecs, $common_pid, $common_comm,
                  $comm, $pid, $prio, $success, $target_cpu) = @_;
           }
           .ft

       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         top

       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):

           .ft C
            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;
           .ft

       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:

           .ft C
            sub trace_begin
            {
            }
           .ft

       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:

           .ft C
           sub trace_end
           {
           }
           .ft

       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:

           .ft C
           sub trace_unhandled
           {
               my ($event_name, $context, $common_cpu, $common_secs,
                   $common_nsecs, $common_pid, $common_comm) = @_;
           }
           .ft

       The remaining sections provide descriptions of each of the
       available built-in perf script Perl modules and their associated
       functions.

AVAILABLE MODULES AND FUNCTIONS         top

       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 representation 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 representation 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         top

       perf-script(1)

COLOPHON         top

       This page is part of the perf (Performance analysis tools for
       Linux (in Linux source tree)) project.  Information about the
       project can be found at 
       ⟨https://perf.wiki.kernel.org/index.php/Main_Page⟩.  If you have a
       bug report for this manual page, send it to
       linux-kernel@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git⟩
       on 2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-31.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

perf                           2018-03-07            PERF-SCRIPT-PERL(1)

Pages that refer to this page: perf-script(1)