[perl5.git] / pod / perldtrace.pod

=head1 NAME

perldtrace - Perl's support for DTrace

=head1 SYNOPSIS

    # dtrace -Zn 'perl::sub-entry, perl::sub-return { trace(copyinstr(arg0)) }'
    dtrace: description 'perl::sub-entry, perl::sub-return ' matched 10 probes

    # perl -E 'sub outer { inner(@_) } sub inner { say shift } outer("hello")'
    hello

    (dtrace output)
    CPU     ID                    FUNCTION:NAME
      0  75915       Perl_pp_entersub:sub-entry   BEGIN
      0  75915       Perl_pp_entersub:sub-entry   import
      0  75922      Perl_pp_leavesub:sub-return   import
      0  75922      Perl_pp_leavesub:sub-return   BEGIN
      0  75915       Perl_pp_entersub:sub-entry   outer
      0  75915       Perl_pp_entersub:sub-entry   inner
      0  75922      Perl_pp_leavesub:sub-return   inner
      0  75922      Perl_pp_leavesub:sub-return   outer

=head1 DESCRIPTION

DTrace is a framework for comprehensive system- and application-level
tracing. Perl is a DTrace I<provider>, meaning it exposes several
I<probes> for instrumentation. You can use these in conjunction
with kernel-level probes, as well as probes from other providers
such as MySQL, in order to diagnose software defects, or even just
your application's bottlenecks.

Perl must be compiled with the C<-Dusedtrace> option in order to
make use of the provided probes. While DTrace aims to have no
overhead when its instrumentation is not active, Perl's support
itself cannot uphold that guarantee, so it is built without DTrace
probes under most systems. One notable exception is that Mac OS X
ships a F</usr/bin/perl> with DTrace support enabled.

=head1 HISTORY

=over 4

=item 5.10.1

Perl's initial DTrace support was added, providing C<sub-entry> and
C<sub-return> probes.

=item 5.14.0

The C<sub-entry> and C<sub-return> probes gain a fourth argument: the
package name of the function.

=back

=head1 PROBES

=over 4

=item sub-entry(SUBNAME, FILE, LINE, PACKAGE)

Traces the entry of any subroutine. Note that all of the variables
refer to the subroutine that is being invoked; there is currently
no way to get ahold of any information about the subroutine's
I<caller> from a DTrace action.

    :*perl*::sub-entry {
        printf("%s::%s entered at %s line %d\n",
               copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
    }

=item sub-return(SUBNAME, FILE, LINE, PACKAGE)

Traces the exit of any subroutine. Note that all of the variables
refer to the subroutine that is returning; there is currently no
way to get ahold of any information about the subroutine's I<caller>
from a DTrace action.

    :*perl*::sub-return {
        printf("%s::%s returned at %s line %d\n",
               copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
    }

=back

=head1 EXAMPLES

=over 4

=item Most frequently called functions

    # dtrace -qZn 'sub-entry { @[strjoin(strjoin(copyinstr(arg3),"::"),copyinstr(arg0))] = count() } END {trunc(@, 10)}'

    Class::MOP::Attribute::slots                                    400
    Try::Tiny::catch                                                411
    Try::Tiny::try                                                  411
    Class::MOP::Instance::inline_slot_access                        451
    Class::MOP::Class::Immutable::Trait:::around                    472
    Class::MOP::Mixin::AttributeCore::has_initializer               496
    Class::MOP::Method::Wrapped::__ANON__                           544
    Class::MOP::Package::_package_stash                             737
    Class::MOP::Class::initialize                                  1128
    Class::MOP::get_metaclass_by_name                              1204

=item Trace function calls

    # dtrace -qFZn 'sub-entry, sub-return { trace(copyinstr(arg0)) }'

    0  -> Perl_pp_entersub                        BEGIN                            
    0  <- Perl_pp_leavesub                        BEGIN                            
    0  -> Perl_pp_entersub                        BEGIN                            
    0    -> Perl_pp_entersub                      import                           
    0    <- Perl_pp_leavesub                      import                           
    0  <- Perl_pp_leavesub                        BEGIN                            
    0  -> Perl_pp_entersub                        BEGIN                            
    0    -> Perl_pp_entersub                      dress                            
    0    <- Perl_pp_leavesub                      dress                            
    0    -> Perl_pp_entersub                      dirty                            
    0    <- Perl_pp_leavesub                      dirty                            
    0    -> Perl_pp_entersub                      whiten                           
    0    <- Perl_pp_leavesub                      whiten                           
    0  <- Perl_dounwind                           BEGIN 

=back

=head1 REFERENCES

=over 4

=item DTrace User Guide

L<http://download.oracle.com/docs/cd/E19082-01/819-3620/index.html>

=item DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD

L<http://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/>

=back

=head1 AUTHORS

Shawn M Moore C<sartak@gmail.com>

=cut
Commit	Line	Data
f993ad5b SM	1	=head1 NAME
	2
	3	perldtrace - Perl's support for DTrace
	4
	5	=head1 SYNOPSIS
	6
	7	# dtrace -Zn 'perl::sub-entry, perl::sub-return { trace(copyinstr(arg0)) }'
	8	dtrace: description 'perl::sub-entry, perl::sub-return ' matched 10 probes
	9
	10	# perl -E 'sub outer { inner(@_) } sub inner { say shift } outer("hello")'
	11	hello
	12
	13	(dtrace output)
	14	CPU ID FUNCTION:NAME
	15	0 75915 Perl_pp_entersub:sub-entry BEGIN
	16	0 75915 Perl_pp_entersub:sub-entry import
	17	0 75922 Perl_pp_leavesub:sub-return import
	18	0 75922 Perl_pp_leavesub:sub-return BEGIN
	19	0 75915 Perl_pp_entersub:sub-entry outer
	20	0 75915 Perl_pp_entersub:sub-entry inner
	21	0 75922 Perl_pp_leavesub:sub-return inner
	22	0 75922 Perl_pp_leavesub:sub-return outer
	23
	24	=head1 DESCRIPTION
	25
	26	DTrace is a framework for comprehensive system- and application-level
	27	tracing. Perl is a DTrace I<provider>, meaning it exposes several
	28	I<probes> for instrumentation. You can use these in conjunction
	29	with kernel-level probes, as well as probes from other providers
	30	such as MySQL, in order to diagnose software defects, or even just
	31	your application's bottlenecks.
	32
	33	Perl must be compiled with the C<-Dusedtrace> option in order to
	34	make use of the provided probes. While DTrace aims to have no
	35	overhead when its instrumentation is not active, Perl's support
	36	itself cannot uphold that guarantee, so it is built without DTrace
	37	probes under most systems. One notable exception is that Mac OS X
	38	ships a F</usr/bin/perl> with DTrace support enabled.
	39
	40	=head1 HISTORY
	41
	42	=over 4
	43
	44	=item 5.10.1
	45
	46	Perl's initial DTrace support was added, providing C<sub-entry> and
	47	C<sub-return> probes.
	48
	49	=item 5.14.0
	50
	51	The C<sub-entry> and C<sub-return> probes gain a fourth argument: the
	52	package name of the function.
	53
	54	=back
	55
	56	=head1 PROBES
	57
	58	=over 4
	59
	60	=item sub-entry(SUBNAME, FILE, LINE, PACKAGE)
	61
	62	Traces the entry of any subroutine. Note that all of the variables
	63	refer to the subroutine that is being invoked; there is currently
	64	no way to get ahold of any information about the subroutine's
65	I<caller> from a DTrace action.
66
67	:perl::sub-entry {
68	printf("%s::%s entered at %s line %d\n",
69	copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
70	}
71
72	=item sub-return(SUBNAME, FILE, LINE, PACKAGE)
73
74	Traces the exit of any subroutine. Note that all of the variables
75	refer to the subroutine that is returning; there is currently no
76	way to get ahold of any information about the subroutine's I<caller>
77	from a DTrace action.
78
79	:perl::sub-return {
80	printf("%s::%s returned at %s line %d\n",
81	copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
82	}
83
84	=back
85
86	=head1 EXAMPLES
87
88	=over 4
89
90	=item Most frequently called functions
91
92	# dtrace -qZn 'sub-entry { @[strjoin(strjoin(copyinstr(arg3),"::"),copyinstr(arg0))] = count() } END {trunc(@, 10)}'
93
94	Class::MOP::Attribute::slots 400
95	Try::Tiny::catch 411
96	Try::Tiny::try 411
97	Class::MOP::Instance::inline_slot_access 451
98	Class::MOP::Class::Immutable::Trait:::around 472
99	Class::MOP::Mixin::AttributeCore::has_initializer 496
100	Class::MOP::Method::Wrapped::__ANON__ 544
101	Class::MOP::Package::_package_stash 737
102	Class::MOP::Class::initialize 1128
103	Class::MOP::get_metaclass_by_name 1204
104
105	=item Trace function calls
106
107	# dtrace -qFZn 'sub-entry, sub-return { trace(copyinstr(arg0)) }'
108
109	0 -> Perl_pp_entersub BEGIN
110	0 <- Perl_pp_leavesub BEGIN
111	0 -> Perl_pp_entersub BEGIN
112	0 -> Perl_pp_entersub import
113	0 <- Perl_pp_leavesub import
114	0 <- Perl_pp_leavesub BEGIN
115	0 -> Perl_pp_entersub BEGIN
116	0 -> Perl_pp_entersub dress
117	0 <- Perl_pp_leavesub dress
118	0 -> Perl_pp_entersub dirty
119	0 <- Perl_pp_leavesub dirty
120	0 -> Perl_pp_entersub whiten
121	0 <- Perl_pp_leavesub whiten
122	0 <- Perl_dounwind BEGIN
123
124	=back
125
126	=head1 REFERENCES
127
128	=over 4
129
130	=item DTrace User Guide
131
132	L<http://download.oracle.com/docs/cd/E19082-01/819-3620/index.html>
133
134	=item DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD
135
136	L<http://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/>
137
138	=back
139
140	=head1 AUTHORS
141
142	Shawn M Moore C<sartak@gmail.com>
143
144	=cut