Have high CPU/memory usage? Read this!

OK, lately I saw a couple of threads on this forum reporting problems with high CPU and/or memory usage. Naturally, this can be caused by a multitude of reasons and usually requires investigation. I decided to post a couple of common reasons and solutions here (this was written with Plesk 11 for Linux in mind, but may be applicable to other versions and products as well, YMMV however).

DISCLAIMER: this information is provided as is and without warranty of any kind (including promise of...

Have high CPU/memory usage? Read this!