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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.

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), 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\n",
                          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\n",
                       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)