Moving the kernel to modern C

What does any of this have to do with how slow a program is? Lots of fast programs are unreadable; I think it was Code Complete that talked about writing a DES decrypter in C that was easy to read, and speeding it up one hundred times by turning it into an unreadable pile of assembly. The Linux kernel uses a lot of those nightmare defines to get maximal inline speed at the cost of clarity and ease of finding the code running. Operator overloading has zero effect on speed.

> I date from the years when tomorrow's weather forecast took 20hrs to run.

Weather forecasting always wants faster computers to do more detailed and accurate forecasts. The National Hurricane Center mentioned for their hurricane forecasts that they post every four hours, they run various simulations, and one of them takes six hours to run, meaning it's never as up to date as the other simulations.