If you ever experienced a missmatch between the performance you expected from a server or application running on Linux you probably started to debug your way into it why the applications performance is not on the expected levels.
With Linux being very mature you get an enormous amounts of helpers and interfaces to debug the performance aspects of the operating system and the applications.
Want to see proof? Here – a map of almost all the thingies and interfaces you got:
Thankfully Brendan Gregg put together a page with videos and further links to drill into those interfaces and methods above.