Benchmarking and profiling Drupal
When attempting to create a large change in Drupal core, or even during the course of developing Drupal sites for clients, often you are
Apache Bench (ab)
General documentation about ab can be found at Apache Bench (ab)
Dummy content and common gotchas
Setting up a performance testing environment
Profiling memory usage
Original article is here, follow that for most of the process: http://derickrethans.nl/xdebug_and_tracing_memory_usage.php