There is a promising patch that adds POSIX_FADV_NOREUSE heuristics, see
http://article.gmane.org/gmane.linux.kernel.mm/65564

    > This will mean that there is no way currently to
    > remove a particular file from the cache on linux.

    Correct. There's not a way to do this for a single file (except running
    POSIX_FADV_DONTNEED twice...).

If only one fadvise64 syscall is performed, the *first* previously
unsused page will somehow not be forgotten.