Fair enough. However, I have a question regarding this. The whole change depends on hardware branch predictors which are not constant across hardware. I am not sure how well the branch predictors were pre-Nehalem/pre-Sandybridge, so if new kernels are used on slightly older hardware, won't they suffer from lack of both software/hardware prefetch hints ? I guess they could have made this a CONFIG_xxx option but may be that was infeasible/cluttering the code further.