[1000100_1000101]

You'd need your OS to support, and be configured to use, a disk mounting option that disables file access timestamps, otherwise reads ARE writes.

[wtallis]

Do any operating systems update file access time after every read operation instead of just at fopen?

[1000100_1000101]

Based on the ~10x performance gain from disabling access timestamps in VxWorks' HRFS, I'd guess it does. I have no idea if that's common or rare.

[trinix912]

...and disable swap.