One of the most used by me option of the "perf timeit" subcommand is --duplicate. It duplicates statements to reduce the overhead of the loop. This is necessary when measure the time of very fast statements. Proposed patch adds this option for CLI of the timeit module.

Similar feature already was proposed in issue21988, but it automatically duplicated statements if they executed too fast. This patch does this only on explicit request. And it affects only command-line interface. You need to duplicate statements manually when use programming interface.