;;; Why does this GCs after creating b?  Try running this with GC_PRINT_STATS=1,
;;; or with GC_DONT_GC=1 if you want to see the memory use rise.

(define size 100000)
(define times 100)

(define b (make-bitvector size))

(do ((t 0 (1+ t)))
    ((= t times) 'done)
  (do ((i 0 (1+ i)))
      ((= i size) 'done)
    (bitvector-set! b i #t)))