[racket] Why parameterize is so sloooow?

I compared parameterize with lexical var
----
> (require rackunit)
> (define my-parameter (make-parameter (box 0)))
> (time 
   (parameterize ([my-parameter (box 0)]) 
     (for ([x (in-range 10000000)]) 
       (set-box! (my-parameter) 
                 (add1 (unbox (my-parameter))))) 
     (check-equal? (unbox (my-parameter)) 10000000))) 
cpu time: 3578 real time: 3610 gc time: 0
> (time 
   (let ([my-parameter (box 0)]) 
     (for ([x (in-range 10000000)]) 
       (set-box! my-parameter 
                 (add1 (unbox my-parameter)))) 
     (check-equal? (unbox my-parameter) 10000000))) 
cpu time: 47 real time: 47 gc time: 0
----

100 times difference!

The same experiment with Common Lisp (SBCL):
----
CL-USER> (setf *a* (list 0))
(0)
CL-USER> (time (progn (loop :for i :from 0 :below 10000000
            :do (setf (car *a*) (+ 1 (car *a*)))) (= (car *a*) 10000000)))
Evaluation took:
  0.063 seconds of real time
  0.062500 seconds of total run time (0.062500 user, 0.000000 system)
  98.41% CPU
  172,464,541 processor cycles
  0 bytes consed
  
T
CL-USER> (let ((a (list 0))) (time (loop :for i :from 0 :below 10000000
            :do (setf (car a) (+ 1 (car a))))) (= (car a) 10000000))
              
Evaluation took:
  0.047 seconds of real time
  0.046875 seconds of total run time (0.046875 user, 0.000000 system)
  100.00% CPU
  132,098,942 processor cycles
  0 bytes consed
  
T
----
Only 1.5 times.

Is it undesirable to use parameterize as replacement for common lisp special variables? What is it designed for then?


-- 
Roman Klochkov
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