“The PLT helped us to understand what our programming instructions were doing along the essential axis of speed and showed us precisely when and where we were introducing slowness to our source code. The PLT told us when to pay attention to the “small efficiencies” Knuth mentioned. It was our 3 percent escape hatch, a way to know for sure that optimization wasn’t “premature.” We were sure each optimization we did was helping to keep performance heading in the right direction.”