This sections covers 3-tools to benchmark webserver (nginx in our case).
In our case, Nginx already has a cached copy of content. You can use static index.html instead. Goal of this test was not to compare to different wordpress setups or caching techniques A v/s caching technique B.
I just wanted to check how many concurrent requests nginx can handle on given Ubuntu server.
Also for clarity concurrency is not equal to page-views or real-users. I will write more on it someday.