> On Mon, 25 Feb 2002, Michael Cohen wrote:
>
> > This one was given to me by WLI himself;
>
> Are you sure these are the latest bit-sparse primes ?
WLI has yet to update me, and I've yet to see anything new from him in this area. I could be mistaken.
> > +++ linux-patched/include/asm-alpha/param.h Mon Feb 25 20:44:35 2002
>
> > +/* SPARSE_GOLDEN_RATIO_PRIME ought to be different for non-32bit arches. */
> > +
> > +#ifndef SPARSE_GOLDEN_RATIO_PRIME
> > +#define SPARSE_GOLDEN_RATIO_PRIME 0x9e004001UL
> > +#endif
>
> > +++ linux-patched/include/asm-arm/param.h Mon Feb 25 20:43:13 2002
> > +#ifndef SPARSE_GOLDEN_RATIO_PRIME
> > +#define SPARSE_GOLDEN_RATIO_PRIME 0x9e004001UL
> > +#endif
>
> Yuck, the fact that you're defining the exact same constant in
> many .h files is ugly. Could you move this to one place ?
> (maybe linux/hash.h like Rusty is doing for 2.5?)
Possible. Take a look at HZ though. It's an arch-specific parameter similar to HZ (different for some arches, but not all) and it looks like it belongs in params.h for that reason.
> > + unsigned long hash;
> > + hash = (unsigned long) mapping + index;
> > + hash *= SPARSE_GOLDEN_RATIO_PRIME;
> > + hash >>= BITS_PER_LONG - PAGE_HASH_BITS;
> > + hash &= PAGE_HASH_SIZE - 1;
> > + return hash;
>
> For 64-bit systems you'll want:
>
> 1) a 64-bit golden ratio prime
> 2) expanding the bit ops by hand because gcc doesn't do
> it for you
> These last 2 points are easy, you can just copy the stuff
> from the struct page patch I sent earlier.
Great, thanks :)
> cheers,
>
> Rik
> --
> "Linux holds advantages over the single-vendor commercial OS"
> -- Microsoft's "Competing with Linux" document
>
> http://www.surriel.com/ http://distro.conectiva.com/
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