Consider POSIX_FADV_NOREUSE?

[Ciprian Craciun]

On Fri, Aug 4, 2023 at 3:24 AM Ronan Pigott via rsync
<rsync at lists.samba.org> wrote:
> Maybe it's time to re-evaluate the utility of posix_fadvise in rsync?


I would be glad to see this option added to `rsync`, especially when
mirroring very large sources / targets and I don't want to trash the
file-system cache.

However, I think any of these variants (either "dontneed" or
"noreuse") should be opt-in, because I often use `rsync -n -c` to see
what would change, and then issue a proper `rsync -c` which would
benefit from the file-system cache.  (Also, "dontneed" might be much
more aggressive than "noreuse".)

(BTW, if one starts implementing `fadvise` and friends, then there are
options to tell the file-system that the whole file would be read,
etc.)

Ciprian.