atime isn't updated on every access. That "relatime" mount option that's almost universally used? It updates atime when the file is written (so mtime and ctime

atime isn't updated on every access. That "relatime" mount option that's almost universally used? It updates atime when the file is written (so mtime and ctime are updated anyway, no extra cost to bumping atime), or after a day if no writes happen but reads.