> The benchmark is a tight loop where the vtable lookup is a big chunk of the total computation. I don't think one can extrapolate this 1.5x improvement to real

> The benchmark is a tight loop where the vtable lookup is a big chunk of the total computation. I don't think one can extrapolate this 1.5x improvement to real code. No you can't. But other things get worse at a bigger scale. Not all programs make those virtual calls absolutely everywhere so the overhead scales with the program, but many don't pay attention to memory access pattern, and cause their instruction pointer to jump all over the place and trash their instruction cache. Mike Acton have once shown that merely reordering objects by types, while keeping those virtual calls, can help the instruction cache quite a bit just by making sure the same code was called several times in a raw.