Re: Moving mac68k to 8K pages?

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

> On Fri, Feb 08, 2019 at 04:40:29AM +0000, John Klos wrote:
> > Are there any good reasons to not switch mac68k to 8K pages, at very least
> > until someone gets around to rewriting the PMAP?
> 
> Haven't thought about it in detail but things to consider:
>  - it wastes a bit of space on tiny memory machines

I guess there are some tradeoff (sparse mappings may wastes pte pages,
but block mappings require less pte pages on large pages).

There was an old dumb benchmark and 8KB page kernel was faster than 4KB
on 68030:
 http://mail-index.netbsd.org/port-m68k/2009/12/09/msg000205.html

>  - does it break binary comptability?

No, m68k userland already uses 8K pages (see ancient COMPAT_M68K4K)
and amiga, atari, news68k, and sun3 kernels already use 8K pages.

Note HPMMU machines doesn't support 8K pages, I guess.

---
Izumi Tsutsui