• First has 40 GB RAM (IBM 3850 M2 / x3950 M2, PCI-E)
• Second has 64 GB RAM (IBM x3950, PCI-X)

• OS Red Hat Enterprise Linux 4.7
• linux kernel 2.6.9-89 x86_64
• perl 5.8.9
• identical processor, disks, etc.

 
use warnings;
use strict;

use JSON::XS;
use Benchmark qw(cmpthese);

my $coder = JSON::XS->new->ascii->pretty->allow_nonref;

my $hashref = { one => 1, two => 2, three => 3, four => { nested => 'b
+ird' } };
my $arrayref = [ 'one', 'two', 'three', 'four', 'five', 'six' ];


# cmpthese can be used both ways as well
cmpthese(
  -1,
  {
    'enc+dec hashref ' =>
      sub { $coder->decode( $coder->encode( $hashref ) ) },
    'enc+dec arrayref ' =>
      sub { $coder->decode( $coder->encode( $arrayref ) ) },
  }
);
__END__
[download]

[me@first ~]$ ./perl-json-test.pl
                      Rate  enc+dec hashref  enc+dec arrayref
enc+dec hashref   344063/s                --              -22%
enc+dec arrayref  438597/s               27%                --

[me@second ~]$ ./perl-json-test.pl
                      Rate  enc+dec hashref  enc+dec arrayref
enc+dec hashref   153121/s                --              -24%
enc+dec arrayref  200972/s               31%                --
[download]

Do any of the honorable monks have made similar observations or even reasonable explanation to why the machine with the most memory is the slower one?

Update 1: Actually, I have 4 machines of which 2 are pairwise identical. Each machine behaves identically as its twin.

Update 2 : Thanks for helpful replies. As I have remote access only to the machines in question, I can't experiment as broadly as I otherwise would have, but I'll surely update this thread once I get some results. I have asked the services provider to reduce physical memory down to 16 Gb.

Update 3 : It turns the machines were not identical after all (see top), and that reducing the memory down to 16 Gb did not significantly change the benchmarks. Whether or not the PCI bus type can account for the huge difference in overall performance is unknown.