Yeah there might be some swapping but no direct files. I converted the benchmark (code below) to use timethese(5) to do some repeating.

Weak machine:

Benchmark: timing 5 iterations of FastMktime::caching_mktime, POSIX::m
+ktime, TIME::Local::timegm_nocheck...
FastMktime::caching_mktime: 120 wallclock secs (120.21 usr +  0.05 sys
+ = 120.26 CPU) @  0.04/s (n=5)
POSIX::mktime: 360 wallclock secs (165.42 usr + 193.81 sys = 359.23 CP
+U) @  0.01/s (n=5)
TIME::Local::timegm_nocheck: 293 wallclock secs (292.72 usr +  0.14 sy
+s = 292.86 CPU) @  0.02/s (n=5)
[download]

stronger machine:

Benchmark: timing 5 iterations of FastMktime::caching_mktime, POSIX::m
+ktime, TIME::Local::timegm_nocheck...
FastMktime::caching_mktime: 65 wallclock secs (64.77 usr +  0.02 sys =
+ 64.79 CPU) @  0.08/s (n=5)
POSIX::mktime: 118 wallclock secs (58.16 usr + 60.47 sys = 118.63 CPU)
+ @  0.04/s (n=5)
TIME::Local::timegm_nocheck: 143 wallclock secs (143.07 usr +  0.54 sy
+s = 143.61 CPU) @  0.03/s (n=5)
[download]

benchmark.t

#!/usr/bin/perl

use FastMktime;
use Benchmark qw(:all);
use POSIX qw(mktime);
use Time::Local;

my $sstart = time;
my $sstop  = $sstart + 1e7;
my @dates;

# Stuff 1e7 sequential datestamps into an array. 
for (my $s=$sstart; $s<$sstop; $s++) {
  push(@dates, [ (gmtime $s)[0..5] ]);
}

my $tmp;
my $results = timethese(1, {
    'POSIX::mktime' => sub { $tmp = POSIX::mktime(@$_) for @dates },
    'TIME::Local::timegm_nocheck' => sub { $tmp = Time::Local::timegm_
+nocheck(@$_) for @dates },
    'FastMktime::caching_mktime' => sub { $tmp = FastMktime::caching_m
+ktime(@$_) for @dates },
});
[download]