I wrote bench_startup.py to measure the startup time on Windows. The precision of the script is quite bad because Windows timer has a bad resolution (e.g. 15.6 ms on Windows 7) :-/

In release mode, the best startup time is 45.2 ms without random, 50.9 ms with random: an overhead of 5.6 ms (12%).

My script uses PYTHONHASHSEED=0 to disable the initialization of CryptoGen. You may modify the script to compare an unpatched Python with a patched Python for better numbers.

An overhead 12% is important. random-6.patch contains a faster (but also weaker) RNG on Windows, disable at compilation time. Search "#if 1" at the end of random.c. It uses my linear congruential generator (LCG) initialized with gettimeofday() and getpid() (which are known to be weak) instead of CryptoGen. Using the LCG, the startup overhead is between 1 and 2%.