pv 使うとか

$ sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'
$ time { < /usr/bin/od od -A nx -t x1 -v; }
:

real 0m0.404s
user 0m0.024s
sys 0m0.005s

$ sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'
$ time { < /usr/bin/od od -A nx -t x1 -v | pv -q -L2M > /dev/null; }
real 0m0.458s
user 0m0.019s
sys 0m0.007s