We have a reasonably well specified server which has 3gb RAM.

It is running a couple of very busy sites on an Ubuntu 6.06 LTS Server
install. The site is written in PHP5 and has a MySQL 5 database.

On occasion, the server just stops and needs to be restarted from the control
panel, so to investigate I have installed munin.

Now I am going to show my noobieness

During normal running most of the ram is shown as allocated to cache, but
at the time the server stops working, and for several hours afterwards, most
of the memory is shown as page_table. At the same time as this drop we
get a huge spike in connections which is probably the lunchtime rush...

I can't find out what page_table means and whether I should be worried
about it. If I should be worried about it I think I know what the problem
is... and it would be code related