I have installed red hat 9.0 on my laptop with 384 MB RAM. When the machine boots, the RAM used is 135 MB. After running some application (Mozilla web browser etc) the memory usage suddenly jumps tp 295-315 MB. This does not goes down even when I close all the application windows.

Per my understanding Linux has a small memory footprint. So why is it taking so much RAM.

I am checking memory usage in System Monitor utility. If I go to Processes tab to see all the processes that are using the memory and total them, I don't see any process with high mem usage.

Thanks.

This is the normal behaviour afaik. A lot of memery is used as a cache to speed up ops. You'll notice that swap will moreless never be used, in windows instead ram is something like 50% free and you'll use always the swap.

to see how much memory you have available use the "free" command and look at the row labeled "-/+ buffers/cache" in column "free". I have a 384M machine and right now free shows 152M free. i have a lot of windows open across 6 desktops (typical) such as: 2 mozilla windows (one with 6 tabs open), evolution, 6 command prompt windows, emacs, redhat-control-network, an xpdf viewer window.

i have an alias called "memhog" which i use when i need to see what's taking up memory:

alias memhog='ps aux | head -1; ps aux | sort +5nr | head -20 | cut -c1-120'

look at columns "vsz & rss". when i need more memory, redhat-control-network is usually the first to go, right now at 30M. it's odd that it can be closed even though still connected to internet. just did, now have 180M free (not sure why you can close the redhat-control-network window while still connected, maybe somebody else can answer that, also why does it take so much memory anyway?).

also, i run my machine with swap turned off because i've found that when it starts using swap space i've probably got stuff using a lot of memory that doesn't need to be there so i get rid of it. having swap turned off may not be the best way for everyone to use redhat v9, but it's what works best for me.

probably answered more than what you were asking, but hope some of it helps