(use extras ports)

(print "read-line")
(time
  (with-input-from-file "world_bank.json"
    (lambda () (port-map identity read-line))))

(print "read-char")
(time
  (with-input-from-file "world_bank.json"
    (lambda () (port-map identity read-char))))

(print "read-string")
(time
  (with-input-from-file "world_bank.json"
    (lambda () (port-map identity (cut read-string 1024)))))

;; Results
;; =======
read-line
0.039s CPU time, 0.011s GC time (major), 9/2 mutations (total/tracked), 6/6 GCs (major/minor), maximum live heap: 3.09 MiB
read-char
1.422s CPU time, 0.588s GC time (major), 8/2 mutations (total/tracked), 9/2574 GCs (major/minor), maximum live heap: 68.2 MiB
read-string
[panic] out of memory - heap has reached its maximum size - execution terminated

...more...
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port
read-string/port        <--