Hey all,

I've got an Ubuntu 9.10 64-bit server that seems to use up all available memory. According to my munin graphs, almost all of the memory used up is in the swap cache, cache, and slab cache. (I take this to mean virtual memory caches, am I right in assuming this?)

Once memory usage approaches 100%, some (although not all) system services such as SSH become sluggish and unresponsive. After rebooting the system, performance and memory usage become normal for a time.

Some interesting tidbits:

• The system runs Apache 2, MySQL, Munin, and sshd.
• The memory usage spikes happen at the same time every night (at 10 PM sharp.)
• There appears to be nothing in the crontab for any of the users, and nothing in /etc/cron.d/* out of the ordinary, let alone something that would occur at 10 PM.

My question is, how do I figure out what is causing the memory suckage? I've tried the usual utilities (e.g. ps, top, etc) but I can't seem to find anything unusual.

Any ideas? Thanks in advance!