On my disk it gives:

name                                 time/op
deco/disk/randread/direct/4K-min     98.0µs ± 1%
deco/disk/randread/direct/4K-avg      104µs ± 0%
deco/disk/randread/direct/1M-min     2.90ms ±17%
deco/disk/randread/direct/1M-avg     3.55ms ± 0%
deco/disk/randread/pagecache/4K-min   227ns ± 1%
deco/disk/randread/pagecache/4K-avg   629ns ± 0%
deco/disk/randread/pagecache/1M-min  70.8µs ± 7%
deco/disk/randread/pagecache/1M-avg  99.4µs ± 1%