(use srfi-4)
(use miscmacros)
(use posix)

(define test-data (make-u8vector (* 1024 1024)))
(define N 1024)
(define t #f)

(printf "Dealing with ~A I/Os of ~A bytes each\n"
        N (u8vector-length test-data))

(printf "write-u8vector:\n")
(set! t (current-milliseconds))
(time
 (with-output-to-file "test.dat"
   (lambda ()
     (repeat N (write-u8vector test-data)))))
(printf "Wall time: ~As\n" (/ (- (current-milliseconds) t) 1000))

(printf "file-write:\n")
(set! t (current-milliseconds))
(time
 (let ((fd (file-open "test2.dat" (+ open/wronly open/creat))))
   (repeat N
           (file-write fd (u8vector->blob/shared test-data)))
   (file-close fd)))
(printf "Wall time: ~As\n" (/ (- (current-milliseconds) t) 1000))

(printf "read-u8vector!:\n")
(set! t (current-milliseconds))
(time
 (with-input-from-file "test.dat"
   (lambda ()
     (repeat N (read-u8vector! (u8vector-length test-data) test-data)))))
(printf "Wall time: ~As\n" (/ (- (current-milliseconds) t) 1000))

(printf "file-read:\n")
(set! t (current-milliseconds))
(time
 (let ((fd (file-open "test2.dat" (+ open/rdonly))))
   (repeat N
           (file-read fd (u8vector-length test-data) (u8vector->blob/shared test-data)))
   (file-close fd)))
(printf "Wall time: ~As\n" (/ (- (current-milliseconds) t) 1000))



Results on my crappy VM:


Dealing with 1024 I/Os of 1048576 bytes each
write-u8vector:
39.82s CPU time, 0.05s GC time (major), 62 mutations, 37/1179479 GCs (major/minor)
Wall time: 44.635s
file-write:
3.26s CPU time, 52 mutations, 0/11 GCs (major/minor)
Wall time: 14.339s
read-u8vector!:
0.46s CPU time, 80 mutations, 0/15 GCs (major/minor)
Wall time: 0.509s
file-read:
0.37s CPU time, 88 mutations, 0/13 GCs (major/minor)
Wall time: 0.38s