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 Perlppentersub:sub-entry BEGIN
0 75915 Perlppentersub:sub-entry import
0 75922 Perlppleavesub:sub-return import
0 75922 Perlppleavesub:sub-return BEGIN
0 75915 Perlppentersub:sub-entry outer
0 75915 Perlppentersub:sub-entry inner
0 75922 Perlppleavesub:sub-return inner
0 75922 Perlppleavesub: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 "${^GLOBALPHASE}" variable,
especially since the values for "NEWPHASE" and "OLDPHASE" are the
strings that "${^GLOBALPHASE}" 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::inlineslotaccess 451
Class::MOP::Class::Immutable::Trait:::around 472
Class::MOP::Mixin::AttributeCore::hasinitializer 496
Class::MOP::Method::Wrapped::ANON 544
Class::MOP::Package::packagestash 737
Class::MOP::Class::initialize 1128
Class::MOP::getmetaclassbyname 1204
Trace function calls
# dtrace -qFZn 'sub-entry, sub-return { trace(copyinstr(arg0)) }'
0 -> Perlppentersub BEGIN
0 <- Perlppleavesub BEGIN
0 -> Perlppentersub BEGIN
0 -> Perlppentersub import
0 <- Perlppleavesub import
0 <- Perlppleavesub BEGIN
0 -> Perlppentersub BEGIN
0 -> Perlppentersub dress
0 <- Perlppleavesub dress
0 -> Perlppentersub dirty
0 <- Perlppleavesub dirty
0 -> Perlppentersub whiten
0 <- Perlppleavesub whiten
0 <- Perldounwind 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 Perlppentersub:sub-entry END
1 77214 Perlppentersub:sub-entry END
1 77214 Perlppentersub:sub-entry cleanup
1 77214 Perlppentersub:sub-entry forcewritable
1 77214 Perlppentersub:sub-entry forcewritable
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
DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD
http://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/
FreeBSD/dp/0132091518/>
AUTHORS
Shawn M Moore "sartak@gmail.com"
perl v5.16.3 2013-03-04 PERLDTRACE(1)