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.

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
",
			  copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
	       }

       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
",
			  copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
	       }

       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
",
		       copyinstr(arg1), 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

REFERENCES

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

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

AUTHORS

       Shawn M Moore "sartak@gmail.com"

perl v5.16.2							    2012-10-25							     PERLDTRACE(1)