orlov/nobh

[Andries Brouwer <Andries.Brouwer@cwi.nl>]

> > +oldalloc                   Use old allocator for new inodes.
> > +orlov              (*)     Use Orlov allocator.
> > +
> > +nobh                       Do not attach buffer_heads to file pagecache.
> 
> For these two it would be nice to include a description
> of why you'd want them or a pointer to something
> describing it. An admin trying to squeeze performance out
> of his server might see these options in such documentation
> and then want to know if they can help him.

See http://lwn.net/Articles/14633/ and http://lwn.net/Articles/14446/
for Orlov.

I am not aware of serious benchmark work. Simple direct tests
seem either to show no significant difference or to favor Orlov.
I have never seen a study on fragmentation after extended use
of both allocators.

Concerning nobh, I think that is a toy by Andrew, meant for
very large machines. He is in a better position to comment
(in fact on both orlov and nobh).

Andries