Problems understanding RAM usage in top

[David <wizzardx@gmail.com>]

Hi list.

Is it normal for 'top' to show that most of your physical memory is
used when there aren't any processes running? (besides the usual init,
getty, klogd, sshd, etc).

I assume that this memory is being used for Linux caches - file
buffers etc to speed up disk access and so on. Is there a way to tell
how much memory the Linux kernel is using, and what for?

I'm busy tracking down OOM killer issues on a server and I'm wondering
if there is a memory leak somewhere (eg: lvm or another kernel
module). Nothing (besides the usuals) is running, but top is showing
900/1024 MB ram used, and 158/1024 MB swap used.

David.