Lexical binding: why?

[Alan Mackenzie]

Hello, Emacs.

What is the purpose of converting Lisp files to use lexical binding?

I always thought the idea was to speed the SW up.  However, when I tried
converting CC Mode to lexical binding, I got the following timings for
two of my personal benchmarks:

                  Dynamic binding             Lexical binding

Benchmark 1           7.249s                      7.423s 

Benchmark 2          16.743s                     16.691s

.  I thus see no speedup from the use of lexical binding.

Have I, perhaps, made some mistake somewhere?  Does anybody else see
significant speed increases through the use of lexical binding?

-- 
Alan Mackenzie (Nuremberg, Germany).