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




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


SEE ALSO

       Devel::DTrace::Provider(3)
           This CPAN module lets you create application-level DTrace probes
           written in Perl.


AUTHORS

       Shawn M Moore "sartak@gmail.com"



perl v5.24.0                      2016-03-01                   PERLDTRACE(1pm)

perl 5.24 - Generated Tue Nov 29 19:00:17 CST 2016
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