Why so many gettimeofday calls?
Gettimeofday is mostly called by Apache to log entries in debug-files. Also some modules use gettimeofday. So nothing to worry about.
EDIT: I did some php source code digging and came up with the following results: Most time related php functions will use the system time. Since they use the system time, gettimeofday will be called a lot so if you want to reducte the calls, reducte your time related functions.
I have to remark though that other functions also make gettimeofday-calls. For example if you use php_session_start, this will (sometimes, depening on a few parameters like if a new session,...) make a call to php_combined_lcg which will make in his turn a call to lcg_seed if there is no seed value set to get a pseudo random number. And lcg_seed will make a gettimeofday call. Keep this in mind.