With the freeware utility CMDtimer you can easily measure execution time of any native AutoCAD command.
Just download the LISP-Reactor CMDtimer from Download, load it into AutoCAD with APPLOAD and run it by typing the command CMDTIMER (repeated command disables it again - acts as a toggle).
The any AutoCAD command simply displays a report (on the command line) about the execution time of that command - e.g.:
CMDtimer> REGEN: 0.531 secs (1798366440 ticks)

It lists the total time in seconds and the exact number of CPU "ticks". In this way you can easily measure the influence of different display settings, fonts or simplified geometry, especially on large drawings (benchmarks).
Of course in interactive commands, the total run time is counted, including the user response time, answering the command prompts. To measure performance, use scripts or macros in this case.