Have you looked at the built-in statistics for this (in the Search App)? From the menu bar, choose;
Status -> Search Activity -> Search Activity Overview
Status -> Search Activity -> Search Detail
Could prove useful.
Yeah I know about that but there are searches that are using a high amount of CPU and want to investigate who is running them and what they are doing. Is this logged in the _internal index? I know when you inspect a search it tells you the PID.