New document for perldtrace

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+=head1 NAME
+
+perldtrace - Perl's support for DTrace
+
+=head1 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
+
+=head1 DESCRIPTION
+
+DTrace is a framework for comprehensive system- and application-level
+tracing. Perl is a DTrace I<provider>, meaning it exposes several
+I<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 C<-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 F</usr/bin/perl> with DTrace support enabled.
+
+=head1 HISTORY
+
+=over 4
+
+=item 5.10.1
+
+Perl's initial DTrace support was added, providing C<sub-entry> and
+C<sub-return> probes.
+
+=item 5.14.0
+
+The C<sub-entry> and C<sub-return> probes gain a fourth argument: the
+package name of the function.
+
+=back
+
+=head1 PROBES
+
+=over 4
+
+=item 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
+I<caller> from a DTrace action.
+
+    :*perl*::sub-entry {
+        printf("%s::%s entered at %s line %d\n",
+               copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
+    }
+
+=item 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 I<caller>
+from a DTrace action.
+
+    :*perl*::sub-return {
+        printf("%s::%s returned at %s line %d\n",
+               copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg0);
+    }
+
+=back
+
+=head1 EXAMPLES
+
+=over 4
+
+=item 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
+
+=item 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 
+
+=back
+
+=head1 REFERENCES
+
+=over 4
+
+=item DTrace User Guide
+
+L<http://download.oracle.com/docs/cd/E19082-01/819-3620/index.html>
+
+=item DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD
+
+L<http://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/>
+
+=back
+
+=head1 AUTHORS
+
+Shawn M Moore C<sartak@gmail.com>
+
+=cut