memory usage after running server

[thµnder]

Hi guys, after running bfserver few times my server uses large amount of
memory, looks like memory is not "cleaned" after crash.
Thats how it looks:

30 processes: 29 sleeping, 1 running, 0 zombie, 0 stopped
CPU states:   0.0% user,   0.0% system,   0.0% nice,  100.0% idle
Mem:    513344K total,   416260K used,    97084K free,    92580K buffers
Swap:        0K total,        0K used,        0K free,   215620K cached

I am only running battlefield on this machine nothing more (its a slackware
8.1 with full installation), after reboot it only uses about 44 Mega Bytes

Im kinda new with linux but i seem to remember this kind of problems from
win9x.
Is there any way to "clean" memory on a linux or do i have to reboot eatch
time server has crashed? ;P