I know it's normal for Linux to use up all available memory (partly for caching)

However when I restart my apache (which serves dynamic pages through php and mysql) I regain quite a bit of memory. (about 240,768 bytes)

vmstat output before and after a restart
===================================
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
.....
0 11 0 154764 12804 201096 477296 213 68 421 68 325 701 2 1 97
0 1 0 55040 153848 201140 477804 241 0 469 101 482 1200 8 7 84
===================================

I was just wondering how to I find out where apache is allocating it's memory? How do I find out how much memory php is using and allocating to mysql connections?

Thanks,
Michael