I have 2 webservers running Apache 2.x on CentOS 5.x. One of them was started like 16 hours ago and has lots of free RAM (about 28GB out of 34GB).
My second server however, is running for a few weeks, and is constantly at 700 MB free RAM, no matter how much traffic there is. If I stop the Apache on it, it frees up another 400MB of RAM, so that isn't the problem. I don't have any other memory-consuming services (like MySQL) installed on it.
I've heard that linux takes free memory and allocates it by default. Is this true? If so, can I disable this? Or is there any other reason this might happen?