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NAME | SYNOPSIS | DESCRIPTION | STARTER SCRIPTS | EVENT HANDLERS | SCRIPT LAYOUT | AVAILABLE MODULES AND FUNCTIONS | SEE ALSO | COLOPHON |
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PERF-SCRIPT-PERL(1) perf Manual PERF-SCRIPT-PERL(1)
perf-script-perl - Process trace data with a Perl script
perf script [-s [Perl]:script[.pl] ]
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.
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.
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_wakeup event defines the following
fields (see
/sys/kernel/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
$common_comm the name of the current process
All of the remaining fields in the event’s format file have
counterparts as handler function arguments of the same name, as
can be seen in the example above.
The above provides the basics needed to directly access every
field of every event in a trace, which covers 90% of what you
need to know to write a useful trace script. The sections below
cover the rest.
Every perf script Perl script should start by setting up a Perl
module search path and 'use’ing a few support modules (see module
descriptions below):
.ft C
use lib "$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, $common_comm) = @_;
}
.ft
The remaining sections provide descriptions of each of the
available built-in perf script Perl modules and their associated
functions.
The following sections describe the functions and variables
available via the various Perf::Trace::* Perl modules. To use the
functions and variables from the given module, add the
corresponding use Perf::Trace::XXX line to your perf script
script.
Perf::Trace::Core Module
These functions provide some essential functions to user scripts.
The flag_str and symbol_str functions provide human-readable
strings for flag and symbolic fields. These correspond to the
strings and values parsed from the print fmt fields of the event
format files:
flag_str($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
perf-script(1)
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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git⟩
on 2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-13.) 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 [email protected]
perf 2023-02-02 PERF-SCRIPT-PERL(1)
Pages that refer to this page: perf-script(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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