perldtrace - Perl's support for DTrace
- # 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
DTrace is a framework for comprehensive system- and application-level tracing. Perl is a DTrace provider, meaning it exposes several 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 -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 /usr/bin/perl with DTrace support enabled.
Perl's initial DTrace support was added, providing sub-entry and
sub-return probes.
The sub-entry and sub-return probes gain a fourth argument: the
package name of the function.
The phase-change
probe was added.
The op-entry
, loading-file
, and loaded-file
probes were added.
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 caller from a DTrace action.
- :*perl*::sub-entry {
- printf("%s::%s entered at %s line %d\n",
- copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg2);
- }
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 caller from a DTrace action.
Traces changes to Perl's interpreter state. You can internalize this
as tracing changes to Perl's ${^GLOBAL_PHASE}
variable, especially
since the values for NEWPHASE
and OLDPHASE
are the strings that
${^GLOBAL_PHASE}
reports.
- :*perl*::phase-change {
- printf("Phase changed from %s to %s\n",
- copyinstr(arg1), copyinstr(arg0));
- }
Traces the execution of each opcode in the Perl runloop. This probe is fired before the opcode is executed. When the Perl debugger is enabled, the DTrace probe is fired after the debugger hooks (but still before the opcode itself is executed).
- :*perl*::op-entry {
- printf("About to execute opcode %s\n", copyinstr(arg0));
- }
Fires when Perl is about to load an individual file, whether from
use, require, or do. This probe fires before the file is
read from disk. The filename argument is converted to local filesystem
paths instead of providing Module::Name
-style names.
- :*perl*:loading-file {
- printf("About to load %s\n", copyinstr(arg0));
- }
Fires when Perl has successfully loaded an individual file, whether
from use, require, or do. This probe fires after the file
is read from disk and its contentss evaluated. The filename argument
is converted to local filesystem paths instead of providing
Module::Name
-style names.
- :*perl*:loaded-file {
- printf("Successfully loaded %s\n", copyinstr(arg0));
- }
- # 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
- # 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
- # dtrace -Zn 'phase-change /copyinstr(arg0) == "END"/ { self->ending = 1 } sub-entry /self->ending/ { trace(copyinstr(arg0)) }'
- CPU ID FUNCTION:NAME
- 1 77214 Perl_pp_entersub:sub-entry END
- 1 77214 Perl_pp_entersub:sub-entry END
- 1 77214 Perl_pp_entersub:sub-entry cleanup
- 1 77214 Perl_pp_entersub:sub-entry _force_writable
- 1 77214 Perl_pp_entersub:sub-entry _force_writable
- # dtrace -qZn 'phase-change /copyinstr(arg0) == "START"/ { self->interesting = 1 } phase-change /copyinstr(arg0) == "RUN"/ { self->interesting = 0 } syscall::: /self->interesting/ { @[probefunc] = count() } END { trunc(@, 3) }'
- lseek 310
- read 374
- stat64 1056
- # dtrace -qZn 'sub-entry { self->fqn = strjoin(copyinstr(arg3), strjoin("::", copyinstr(arg0))) } op-entry /self->fqn != ""/ { @[self->fqn] = count() } END { trunc(@, 3) }'
- warnings::unimport 4589
- Exporter::Heavy::_rebuild_cache 5039
- Exporter::import 14578
http://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/
This CPAN module lets you create application-level DTrace probes written in Perl.
Shawn M Moore sartak@gmail.com