Memory management on Fedora6

[Takatsugu Kobayashi]

Hi, Linux newbie here.

I have been using Fedora6 x86_64 for 2 months now and am very happy with 
this package.

I have just noticed that my memory usage does not diminish as I think I 
free up memory by closing applications, etc. I was using Windows before 
migrating into Linux, but on Windows memory was freed up by closing 
applications and by removing inputs from memory cells. How can I free up 
memory on Linux?

Also, I tried Suse 10.2 before using Fedora6. For some reason, response 
time was better on Suse. It looks like opening Mozilla and Openoffice 
applications takes a while..... Does anyone notice this difference in 
response time?

My system configuration is

CPU: Athlon X2 5200 AM2 (not overclocked)
RAM: Wintec DDR2 800 4GB
GPU: Nvidia Geforce 6150 Onboard

Any suggestions for memory management or is this something I don't have 
to worry about?

Thank you very much.

Taka