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PERLDTRACE(1)	       Perl Programmers	Reference Guide		 PERLDTRACE(1)

NAME
       perldtrace - Perl's support for DTrace

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

DESCRIPTION
       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.

HISTORY
       5.10.1
	   Perl's initial DTrace support was added, providing "sub-entry" and
	   "sub-return"	probes.

       5.14.0
	   The "sub-entry" and "sub-return" probes gain	a fourth argument: the
	   package name	of the function.

       5.16.0
	   The "phase-change" probe was	added.

       5.18.0
	   The "op-entry", "loading-file", and "loaded-file" probes were
	   added.

PROBES
       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
	   caller from a DTrace	action.

	    :*perl*::sub-entry {
		printf("%s::%s entered at %s line %d\n",
		      copyinstr(arg3), copyinstr(arg0),	copyinstr(arg1), arg2);
	    }

       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 caller
	   from	a DTrace action.

	    :*perl*::sub-return	{
		printf("%s::%s returned	at %s line %d\n",
		      copyinstr(arg3), copyinstr(arg0),	copyinstr(arg1), arg2);
	    }

       phase-change(NEWPHASE, OLDPHASE)
	   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));
	    }

       op-entry(OPNAME)
	   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));
	    }

       loading-file(FILENAME)
	   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));
	    }

       loaded-file(FILENAME)
	   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 contents 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));
	    }

EXAMPLES
       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

       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

       Function	calls during interpreter cleanup
	    # 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

       System calls at compile time
	    # 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

       Perl functions that execute the most opcodes
	    # 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

REFERENCES
       DTrace Dynamic Tracing Guide
	   <http://dtrace.org/guide/preface.html>

       DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD
	   <https://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/>

SEE ALSO
       Devel::DTrace::Provider
	   This	CPAN module lets you create application-level DTrace probes
	   written in Perl.

AUTHORS
       Shawn M Moore "sartak@gmail.com"

perl v5.32.0			  2020-06-14			 PERLDTRACE(1)

NAME | SYNOPSIS | DESCRIPTION | HISTORY | PROBES | EXAMPLES | REFERENCES | SEE ALSO | AUTHORS

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