use Perl

This started off as a user reporting that Class::Accessor::Grouped was way slower on 5.10 than on 5.8.8. At this point, I call 'not it'...but only because I really don't know what in the hell is going on.

Two brand new fresh FreeBSD 6.2 installs. One with a a compiled (not ports) Perl 5.8.8 and the other with a compiled 5.10.0.

The test case is simple set_inherited, sans C::A::G in the picture, since the reporter noted set was slower as well (which BTW has no MRO interaction):

test.pl
> use lib '.';
> use Foo;
> use Benchmark ':all';
>
> my $f = bless {}, 'Foo';
>
> timethese(0, {
> set_inherited_class => sub {Foo->set_inherited('bar', 'baz')},
> set_inherited_object => sub {$f->set_inherited('bar', 'baz')}
> });

Foo.pm
> package Foo;
> use Scalar::Util qw/blessed reftype/;
>
> sub set_inherited {
> my ($self, $set, $val) = @_;
>
> if (blessed $self) {
> if (reftype $self eq 'HASH') {
> return $self->{$set} = $val;
> } else {
> croak('Cannot set inherited value on an object instance that is not hash-based');
> };
> } else {
> no strict 'refs';
>
> return ${$self.'::__cag_'.$set} = $val;
> };
> }
>
> 1;

The results are:

Perl 5.8.8 Machine:
> Benchmark: running set_inherited_class, set_inherited_object for at least 3 CPU seconds...
> set_inherited_class: 4 wallclock secs ( 3.16 usr + 0.00 sys = 3.16 CPU) @ 575596.40/s (n=1821223)
> set_inherited_object: 3 wallclock secs ( 3.16 usr + -0.01 sys = 3.15 CPU) @ 687794.82/s (n=2165479)
> claco@fbsd588 ~ $

Perl 5.10.0 Machine:
> Benchmark: running set_inherited_class, set_inherited_object for at least 3 CPU seconds...
> set_inherited_class: 3 wallclock secs ( 3.12 usr + 0.01 sys = 3.13 CPU) @ 335388.09/s (n=1050708)
> set_inherited_object: 2 wallclock secs ( 3.15 usr + 0.00 sys = 3.15 CPU) @ 412676.76/s (n=1299287)
> claco@fbsd510 ~ $

My to my shock, if I whittle down the code in set_inherited to just this:

> package Foo;
> use Scalar::Util qw/blessed reftype/;
>
> sub set_inherited {
> my ($self, $set, $val) = @_;
>
> }
>
> 1;

performance still seriouesly sucks:

5.8.8
> Benchmark: running set_inherited_class, set_inherited_object for at least 3 CPU seconds...
> set_inherited_class: 3 wallclock secs ( 3.08 usr + 0.02 sys = 3.09 CPU) @ 1199923.07/s (n=3712262)
> set_inherited_object: 4 wallclock secs ( 3.27 usr + 0.00 sys = 3.27 CPU) @ 1380589.06/s (n=4519272)
> claco@fbsd588 ~ $

5.10.0
> Benchmark: running set_inherited_class, set_inherited_object for at least 3 CPU seconds...
> set_inherited_class: 4 wallclock secs ( 3.09 usr + 0.01 sys = 3.10 CPU) @ 536733.34/s (n=1664712)
> set_inherited_object: 4 wallclock secs ( 3.13 usr + 0.00 sys = 3.13 CPU) @ 638055.42/s (n=1998908)
> claco@fbsd510 ~ $

A this point, I'm stumped. Just my ($, $, $) = @_ is slow. Changing that to:

my $self = shift;
my $set = shift;
my $val = shift

make 5.10 even facter than 5.8.8 again. I know shift is always faster...but why is 5.10 way slower than 5.8.8 when assigning @_?

My brain hurts.