I have a simple drupal 7 installation width 50 modules but something inside it is not working properly.
The installation is temporary hosted in a dedicated server with a 4 core Xeon 2.8 GHz, the big problem is that a simple page load burn 20% or 10% of CPU.
The problem is obviously for the authenticated users, because the NON authenticated have the page cached.
I've tryed removing every modules and i got finally 1/2 % of the CPU on a page load, so the problem is basically stored in one module or in a module setting.
I can provide an ssh user and the admin for drupal 7, i've already installed xhprof, devel etc and here we i need someone good in debugging and find where is the problem.
Seasoned drupal developer, have been working with drupal exclusively for 5+ years (since drupal 5 version). For further information, see message attached.
It depends from count of hooks, modules used. Also some caching can be added for logged in users. Another thing - to enable debugger and xhprof tool. Also memcached, varnish can be used. And nice trick is to move MySQL temp files to memory. So main point to find a bottleneck of project (if it is Commerce, btw, i know where it comes from)