Why DBI (DBD::Pg) takes so much memory ?

Hi,

I have a simple perl program (see below) with DBI call to connect to the
Postgresql db on a CentOS system.  I don't know why the top command
shows it takes more than 110m (under VIRT column).  I tried with newer
DBI and DBD versions still have the same result.  However, I tried it on
host with Mandriva, and it only takes about 8m.  Is there any special on
CentOS or some of the libraries are not linked or built correctly ?

Thanks,
Gary

----- OS Version
$ cat /proc/version
Linux version 2.6.18-194.8.1.el5 (mockbuild@builder10.centos.org) (gcc
version 4.1.2 20080704 (Red Hat 4.1.2-48)) #1 SMP Thu Jul 1 19:04:48 EDT
2010

----- DBI & DBD::Pg versions
$ perl -e 'use DBI; print "$DBI::VERSION\n"'
1.607
2:46pm 675 sd3dev1@sd3dev1:~/tmp$ perl -e 'use DBD::Pg; print
"$DBD::Pg::VERSION\n"'
2.11.5

----- libpq version
$  ldd
/usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi/auto/DBD/Pg/Pg.so
         libpq.so.4 => /usr/lib64/libpq.so.4 (0x00002b8adedb7000)
         libm.so.6 => /lib64/libm.so.6 (0x00002b8adefd9000)
         libc.so.6 => /lib64/libc.so.6 (0x00002b8adf25c000)
         libssl.so.6 => /lib64/libssl.so.6 (0x00002b8adf5b4000)
         libcrypto.so.6 => /lib64/libcrypto.so.6 (0x00002b8adf800000)
         libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x00002b8adfb51000)
         libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00002b8adfde7000)
         libresolv.so.2 => /lib64/libresolv.so.2 (0x00002b8ae001f000)
         libnsl.so.1 => /lib64/libnsl.so.1 (0x00002b8ae0234000)
         libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b8ae044d000)
         /lib64/ld-linux-x86-64.so.2 (0x00000039ffa00000)
         libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2
(0x00002b8ae0668000)
         libcom_err.so.2 => /lib64/libcom_err.so.2 (0x00002b8ae0896000)
         libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3
(0x00002b8ae0a99000)
         libdl.so.2 => /lib64/libdl.so.2 (0x00002b8ae0cbe000)
         libz.so.1 => /usr/lib64/libz.so.1 (0x00002b8ae0ec2000)
         libkrb5support.so.0 => /usr/lib64/libkrb5support.so.0
(0x00002b8ae10d7000)
         libkeyutils.so.1 => /lib64/libkeyutils.so.1 (0x00002b8ae12df000)
         libselinux.so.1 => /lib64/libselinux.so.1 (0x00002b8ae14e2000)
         libsepol.so.1 => /lib64/libsepol.so.1 (0x00002b8ae16fa000)


----- test program
#! /usr/local/bin/perl -w

use strict;
use DBI;

my $data_source = "dbi:Pg:dbname='dev1';host='db1'";
my $dbh = DBI->connect ($data_source, 'user', 'passwd')
     or die "Failed to connect";

sleep 600;
exit;