After some days of work (Using suspend-to-ram during the night) I notice I loose more and more available memory. Even when I close all applications the situation doesn't improve. I even went down to the command line and closed ALL running processes except the init process and the bash I'm working in. I unmounted all these ram disks which Ubuntu is using, I even unloaded all modules which could be unloaded. But still "free" tells me that 1 GB of RAM is used (without buffers/cache). In "top" there is no visible process which occupies all this memory. The only way to free the memory is restarting the machine.

How can I find out where I lose all this memory? Is there a known "suspect" who can cause a problem like this? I'm using Ubuntu 9.10 64 bit on a Dell Latitude E6500 (4 GB RAM) with the latest closed-source nvidia driver and Gnome with Compiz. The applications I use most of the time are firefox and eclipse.

Any hints how I can find the problem? I'm not a kernel hacker so if the solution is patching the kernel or something like that then I might be out of the game...