I think you are simplifying a bit. AFAIK, the slow performance of mod_php is a result of the massive memory foot-print that each Apache worker process will have

I think you are simplifying a bit. AFAIK, the slow performance of mod_php is a result of the massive memory foot-print that each Apache worker process will have. The operating system can cache hundreds of 10 KB PHP files without problem, it doesn't make a difference how many files you have when they are all small and cached. So, in conclusion, I propose that PHP performance is OK if you use something like php-fpm.