Actually they arn't meaningless. The fact that I have to do 1_000_000 iterations before I can even tell the difference between the different access method shows me that this isn't a good place to try and improve performance. Unless of course you are doing millions and millions and millions of these accesses every second, then you might care, but i'm betting if thats the case you'd better have some beefy hardware anyways ;)

I read your node - interesting, thanks. But I can't get results like yours. Could it be because the number of iterations in your test are too low?

Putting get_value() and get_value2() declarations at the beginning of program after the "my $self" line, I get:

              Rate    normal optimized    direct
normal    174625/s        --      -27%      -60%
optimized 240602/s       38%        --      -45%
direct    435374/s      149%       81%        --
[download]

Moving the subs to just above sub a() declaration, I get

              Rate    normal optimized    direct
normal    172275/s        --      -28%      -61%
optimized 239252/s       39%        --      -46%
direct    444444/s      158%       86%        --
[download]

I've tried a few more re-arrangements of the code layout, and I can't get the reversal that you did. All re-arrangements I've tried have 'direct' at 145-155%. Any chance you can post the code so I can duplicate the results? Logically, I would think that asking for the value of an arrayref element is going to be faster than calling a sub to do so, so the benchmarks appear to be logical to me.

I revised the code slightly:

use Benchmark 'cmpthese';

sub get_value {
        my $self = shift;
        return $self->[0];
}

sub get_value2 {
        $_[0]->[0];
}

my $self = bless [123], '::main';

cmpthese( 16000000, {
        normal    => sub { $self->get_value() },
        optimized => sub { $self->get_value2() },
        direct    => sub { $self->[0] },
});

exit(0);

$ perl oo_benchmark.pl 
                Rate    normal optimized    direct
normal     1462523/s        --      -21%      -90%
optimized  1858304/s       27%        --      -88%
direct    15238095/s      942%      720%        --
[download]

Yes, it took 16 million iterations to get an accurate reading on the direct attribute access. With a variant of your original benchmark modified to avoid the double-dispatch penalty, I get:

use Benchmark 'cmpthese';

my $self = bless [123], '::main';

cmpthese( 16000000, {
        normal    => sub { $self->get_value() },
        optimized => sub { $self->get_value2() },
        direct    => sub { $self->[0] },
});

exit(0);

sub get_value {
        my $self = shift;
        return $self->[0];
}

sub get_value2 {
        $_[0]->[0];
}

$ perl oo_benchmark.pl 
                Rate    normal optimized    direct
normal     1725998/s        --      -14%      -94%
optimized  2007528/s       16%        --      -93%
direct    29629630/s     1617%     1376%        --
[download]

That represents speedups of around 20%, 11%, and 100%, respectively. I can make the case for a 10% speedup perhaps, but the others are way outside anything I can explain. Thus I'm not sure this benchmark is useful.