[Samba] samba can use swap space?

[updatemyself .]

Hai all,

i am having a doubt..
samba can use swap space or only physical memory...?

right now i have 4 GB RAM in my File Server
also 4GB SWAP space, i know swap space usage while be less when i have more
then 1GB ram...
that's why i created like this.. (other wise i know SWAP=2 x ram)

but my problem is.. even the RAM usage race maximum.. ( free mem is.. just
or less then 5MB )
swap space will not be suing........

this servers are dedicated file server...(only samba)  with GPFS file
system...
(always having 400 connection.. most of the files in share are more then 100
MB)

my current samba version is...
samba-3.0.20b-2

i already compiled samba-3.0.21b-3 and waiting to get some down time to
upgrade
also i am planing to upgrade my physical memory to 8GB

if any point let me know why my servers are not using swap space
also if anyway to make it use the swap space..

status................
                   total       used       free     shared    buffers
cached
Mem:          4052       4036         16          0         36        732
-/+ buffers/cache:       3266        785
Swap:         4094          0       4094

the reason of my doubt is.. all my file server have the same issue....
all are same configuration...
and when i get more then 400 connection some times the server will be really
slow..

give me some ideas..

Thank you in advance,
Jerrynikki