[ale] monitoring memory

[John Heim]

I'm managing a web server  that runs a application written in mod_perl with 
a mysql backend. I've had problems running out of memory.
We've had occasional OOM events and we've also had mysql crashes due to 
exceeding the maximum number of allowed connections.

I've tweeked the apache and mysql settings but what I'd really like to know 
is if there is some way to tell if I'm close to running out of RAM.

Would the load average be a clear sign? Any other tools? How about 'free'?

Notes:
I didn't write this software and can't alter it. I figure what's happening 
is that the mysql connections never get closed. They timeout eventually.

When it ran out of mysql connections, I increased the max_connections from 
100 to 250. But since I'd already seen OOM events in the past, I figured I'd 
see even more after changing that. So I set the mysql timeout to 60 
seconds -- which, btw, defaults to 8 hours -- and i decreased the apache 
max_ maxClients setting from the default of 150 to 32.