[PPC64] Improved VSID allocation algorithm

[David Gibson]

On Thu, Sep 30, 2004 at 04:40:37PM +1000, Anton Blanchard wrote:
>  
> > This patch went into 2.6.9-rc2-bk2, and my p640 does not boot anymore.
> > Hangs after 'returning from prom_init', wants a power cycle.
> 
> How much memory do you have? We might be filling up a hpte bucket
> completely with certain amounts of memory.

Bugger, bugger, bugger bugger.  That's it.  Just ran 4GB linear
mapping with 4k pages through by hash scattering simulator - max
bucket load is 2 with the old algo and 16 with the new one.  Well, we
just found the first case where the new algorithm scatters
significantly worse than the old one.  It would be something this
dire, wouldn't it.

-- 
David Gibson			| For every complex problem there is a
david AT gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson