It really depends on what you are modeling. For mysql there are a few different definitions for simultaneous users.
- Number of database connections, including idles that only take up memory.
- Number of running queries.
- Number of queries active in the database engine. This is typically ignored.
With a typical web application, you may have a hundred connections open to the database, but only a handful actually running queries at any single time. You can view this number by running
SHOW STATUS LIKE 'Threads_running';. Perhaps run it in a loop and see how it changes. Benchmarking the inactive connections is typically a waste as they just use some memory and not much cpu. So if your application only is running x number of concurrent queries at a time, might as well only benchmark x, even if it's a small number.