Xuan Baldauf wrote:
> * Tails-directories are slower by factor 3.7 than notails-directories. Is there any
> way to optimize? My intuition says that tails-directories should be faster than
> notails-directories, because due to the less data to be read, there should be less
> disk accesses needed to do the same accesses. Why does this reasoning not apply?
>
It is because of the stupid place we put the stat data and directory entries, which
was never what I
desired but got into the code back in the days when I managed remotely, and we were
going to fix it
before shipping to Linus, and then code freeze for 2.4 hit. Plan A would put stat
data and
directory entries together, and would put them in the same packing locality as their
corresponding
file bodies.
It will go into 2.4, along with plan B, and users will be able to choose which one
matches their
application. There actually are applications for which our current layout is optimal,
but recursive
directory traversals are not it.
> >
> >
> > I'm not so sure it makes sense to include this hash in the standard
> > kernel, because it's very special purpose - or we would end up with a
> > hundred different hashes for different uses. I'm not so sure that's what
> > we want?
>
> I'd like the idea of a hash module|plugin together with a 4-byte-hash-name or so
> stored in every directory. Or more general, every directory has a directory_format
> field in it's data structures, so alternative formats (like hashless stem
> compression, etc.) can be implemented.
Agreed.
>
> Xu�n.
