Use /proc/smaps to show the difference between resident and proportional set size memory

pss-demo.pl

#!/usr/bin/env perl
use strict;
use warnings;
use Linux::Smaps;

sub print_memusage {
  my $smaps = Linux::Smaps->new;
  printf "% 6s % 9d % 9d KB % 9d KB\n", $_[0], $$, $smaps->rss, $smaps->pss;
}

my @bigarray = (1..1_000_000);
print " LABEL       PID       RSS          PSS\n";
my $pid = fork;
die "failed to fork $!" unless defined $pid;
if ($pid == 0) {
  print_memusage("CHILD");
  exit;
}
print_memusage("PARENT");
waitpid $pid, 0;