Logs monitoring

I have been asked from one my friends who hosts many websites on single machine to help him to find which vhost is doing some slow requests.

the load of the machine from 0.5 has become 1.5. and there are some apache processess eating the CPU.

It is obvious that some php file is slowing down all the machine but who?

I found this wonderfull tool in Internet

http://code.google.com/p/wtop/wiki/Installing

http://code.google.com/p/wtop/wiki/LogrepCookbook

With this script I can monitor all the pages and not sitting in the dark while some evil pages are drying the CPU power.