Why does my script use so much more memory when run with mod_perl?

StackOverflow https://stackoverflow.com/questions/1606364

Question

I'm trying to learn how to profile perl memory.

I have a very simple Perl hello-world script and I want to know its size in memory.

I use GTop utility to measure the memory (recommended in mod_perl book by Stas Beckman). GTop provides the results that confuse me.

When I run the script from the command line GTop says: 7M.

When I run it under mod_perl, GTop says: 54M.

Why so much?!

Why script memory grows so much under mod_perl? Or maybe I measure the memory in a wrong way? How do you profile perl script memory?

Here are the script and its output (I have added commas manually to easily read the numbers)

  1. Run from command-line

    > perl simple.pl 

size: 7,282688
share: 2,027520
diff: 5,255168

  2. Run under mod_perl

    size: 54,878208
share: 4,661248
diff: 50,216960

Script simple.pl

#!/usr/bin/perl

use strict;
use warnings;
use CGI ();

my $cgi = CGI->new;

print $cgi->header('text/plain');

use GTop;

print "Hello, world!\n";
my $m = GTop->new->proc_mem($$);
print "size: ".$m->size."\n";
print "share: ".$m->share."\n";
my $diff = $m->size - $m->share;
print "diff: $diff\n";
Was it helpful?

Solution

I guess when you run your script under mod_perl, you get your script's memory usage, plus mod_perl's, plus apache's.

See also the answers to these questions:

Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top