220 lines
7.3 KiB
Plaintext
220 lines
7.3 KiB
Plaintext
perf-trace-perl(1)
|
|
==================
|
|
|
|
NAME
|
|
----
|
|
perf-trace-perl - Process trace data with a Perl script
|
|
|
|
SYNOPSIS
|
|
--------
|
|
[verse]
|
|
'perf trace' [-s [Perl]:script[.pl] ]
|
|
|
|
DESCRIPTION
|
|
-----------
|
|
|
|
This perf trace option is used to process perf trace 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
|
|
---------------
|
|
|
|
You can avoid reading the rest of this document by running 'perf trace
|
|
-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-trace.pl script, while not interesting for its results,
|
|
attempts to exercise all of the main scripting features.
|
|
|
|
EVENT HANDLERS
|
|
--------------
|
|
|
|
When perf trace 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_handled' 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 -c 1 -f -a -M -R -e sched:sched_wakeup
|
|
|
|
Traces meant to be processed using a script should be recorded with
|
|
the above options: -c 1 says to sample every event, -a to enable
|
|
system-wide collection, -M to multiplex the output, and -R to collect
|
|
raw samples.
|
|
|
|
The format file for the sched_wakep event defines the following fields
|
|
(see /sys/kernel/debug/tracing/events/sched/sched_wakeup/format):
|
|
|
|
----
|
|
format:
|
|
field:unsigned short common_type;
|
|
field:unsigned char common_flags;
|
|
field:unsigned char common_preempt_count;
|
|
field:int common_pid;
|
|
field:int common_lock_depth;
|
|
|
|
field:char comm[TASK_COMM_LEN];
|
|
field:pid_t pid;
|
|
field:int prio;
|
|
field:int success;
|
|
field:int target_cpu;
|
|
----
|
|
|
|
The handler function for this event would be defined as:
|
|
|
|
----
|
|
sub sched::sched_wakeup
|
|
{
|
|
my ($event_name, $context, $common_cpu, $common_secs,
|
|
$common_nsecs, $common_pid, $common_comm,
|
|
$comm, $pid, $prio, $success, $target_cpu) = @_;
|
|
}
|
|
----
|
|
|
|
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
|
|
$common_comm the name of the current process
|
|
|
|
All of the remaining fields in the event's format file have
|
|
counterparts as handler function arguments of the same name, as can be
|
|
seen in the example above.
|
|
|
|
The above provides the basics needed to directly access every field of
|
|
every event in a trace, which covers 90% of what you need to know to
|
|
write a useful trace script. The sections below cover the rest.
|
|
|
|
SCRIPT LAYOUT
|
|
-------------
|
|
|
|
Every perf trace Perl script should start by setting up a Perl module
|
|
search path and 'use'ing a few support modules (see module
|
|
descriptions below):
|
|
|
|
----
|
|
use lib "$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;
|
|
----
|
|
|
|
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:
|
|
|
|
----
|
|
sub trace_begin
|
|
{
|
|
}
|
|
----
|
|
|
|
*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:
|
|
|
|
----
|
|
sub trace_end
|
|
{
|
|
}
|
|
----
|
|
|
|
*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:
|
|
|
|
----
|
|
sub trace_unhandled
|
|
{
|
|
my ($event_name, $context, $common_cpu, $common_secs,
|
|
$common_nsecs, $common_pid, $common_comm) = @_;
|
|
}
|
|
----
|
|
|
|
The remaining sections provide descriptions of each of the available
|
|
built-in perf trace Perl modules and their associated functions.
|
|
|
|
AVAILABLE MODULES AND FUNCTIONS
|
|
-------------------------------
|
|
|
|
The following sections describe the functions and variables available
|
|
via the various Perf::Trace::* Perl modules. To use the functions and
|
|
variables from the given module, add the corresponding 'use
|
|
Perf::Trace::XXX' line to your perf trace script.
|
|
|
|
Perf::Trace::Core Module
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
These functions provide some essential functions to user scripts.
|
|
|
|
The *flag_str* and *symbol_str* functions provide human-readable
|
|
strings for flag and symbolic fields. These correspond to the strings
|
|
and values parsed from the 'print fmt' fields of the event format
|
|
files:
|
|
|
|
flag_str($event_name, $field_name, $field_value) - returns the string represention 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 represention 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 trace:
|
|
|
|
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
|
|
--------
|
|
linkperf:perf-trace[1]
|