These are the plots.
- Time to compile using mk (which spawns concurrent compilations). The old scheduler is SMP, the new one is AMP.
- Time to compile using pmk (with the source tree hosted in ram), a fake build tool just for this benchmark. It spawns all compilations at once and then waits for all of them.
Draw your own conclussions. No wonder a micro-benchmark could be designed such that AMP always achieves a speed up as we add more cores. It's a pity that in the real world there are always dependencies between independent things.