Re: [PATCH] Radix-tree pagecache for 2.5

[Rik van Riel]

On Tue, 29 Jan 2002, Linus Torvalds wrote:
> On Tue, 29 Jan 2002, David S. Miller wrote:
> >
> > I like the changes too, but I'd like to see some numbers
> > as well.
>
> Absolutely. Even something as simplistic as "lmbench file re-read" changed
> by 0.1% or something. I definitely believe in the scalability part (as
> long as the different processes don't all touch the same mapping all the
> time), so I'm more interested in the "what is the impact of the hash chain
> lookup/walk vs the radix tree walk" kinds of numbers.

There's another nice advantage to the radix tree.

We can let oracle shared memory segments use 4 MB pages,
but still use the normal page cache code to look up the
pages.

With a radix tree there is no overhead in using different
page sizes since we'll just run into them in the tree.

(as opposed to the horrors of trying a hash lookup with
multiple page orders)

regards,

Rik
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