> I would like to be able to set noatime as a mount option so I can
> choose what filesystems I want noatime on and not.
Rather than just setting atime to on or off, it would be useful to
allow an atime delta, to specify how accurate an atime value was
required. For example, if a file system were mounted with
adelta=86400, the atime value of the files on this file system would
only be updated if the current atime value is more than 86400 seconds
(i.e., one day) ago.
This would avoid the need to perform an inode write each time a file
is accessed, while still providing a good indication of which files
can be safely rolled off to a tape archive after having not been
accessed for 6 months. Setting adelta=1 would yield the current
behavior, and adelta=0 could be interpreted as 'no atime'.
VAX/VMS provided such a capability, so there's some past practice with
such a scheme. On VMS, IIRC, the adelta value was settable on a
file-by-file basis, with newly created files inheriting a default from
their parent directory. Given the current inode space shortage, this
would have to wait for ext3. However, providing this feature on a
file system basis seems like something that could be added to the
existing no-atime code fairly easily.
-- John Kodis.