memtest question on 8 GB RAM AMD64 system

[Dino Vliet]

Dear freebsd people,

I have just installed 4 x 2gb kingston memory banks (Kingston HyperX 4GB 800mhz DDR2 Non-ECC CL5 (5-5-5-15) DIMM) onto my AMD 64 system with a X2 5200 CPU. The motherboard I have in this system is MSI K9AG Neo2-Digital.

The system boots fine and I wanted to try memtest to see if there would be errors. So I installed that /usr/ports/sysutils/memtest port and did 

# memtest 2400

The output I got is:
Continuing with unlocked memory; testing will be slower and less reliable.

.......
pagesize 4096
pagesizemask is 0xfffffffffffff000
want 2400MB (2516582400 bytes)
got   2400MB (2516582400 bytes), trying mlock .......failed for unknown reason
Loop 1:
.....

In my /etc/rc/conf file I had added these lines in the past (when I had 4gb RAM installed in it)

sysctl -w kern.ipc.shmmax=1954311424
sysctl -w kern.ipc.shmall=238000

What is the case here? Why is memtest failing to use mlock? How can I eventually make sure I can run memtest with 8000mb? 

The purpose of this machine is that it will be used for a various data intensive tasks where I need to be able to allocate as much memory possible. I am running a postgresql database server on it as well to store my source data.

Brgds
Dino