Re: fix CONFIG_HIGHPTE

William Lee Irwin III
2002-08-07T01:51:53Z

At some point in the past, Andrew Morton wrote:
>> We're piling more and more crap in there to support these pte_chains.
>> How much is too much?
>> Is it likely that large pages and/or shared pagetables would allow us to
>> place pagetables and pte_chains in the direct-mapped region, avoid all
>> this?

On Wed, Aug 07, 2002 at 11:07:52AM +1000, Anton Blanchard wrote:
> On ppc64 shared pagetables will require significant changes to the way
> we handle the hardware hashtable. So add that to the "more and more crap
> in there to support these pte_chains"
> Will shared pagetables be a requirement or can we turn it on per arch?
> Anton

Actually shared pagetables require significant semantic changes in rmap,
e.g. every usage of ptep_to_mm() is broken by shared pagetables and
tracking down assumptions that the (pte, mm) relation is 1:1 is ugly
too. The existing patch for it is not prepared to cope with these.

If they're not already sitting in a back room in ozlabs or Austin
somewhere I'll ship the 3 or 4 singletask 64-bit pagetable OOM's to LTP
etc. to help dispel the 32-bit pagetable space myth, too.

Cheers,
Bill