How to control resource usage of my website?
Use the Devel module It should show you a list of queries run when
the page is loaded and the time taken to run the query. From there
you can check which query is coming from which module.
You can also try a PHP profiler which gives you a lot of metrics.
Or try disabling your modules one at a time to decide when the load
time gets really high
Another option lies in smarter caching