Re: What to do with slow Chip/ST RAM

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

abs%NetBSD.org@localhost wrote:

> On Wed, 11 Mar 2009, Izumi Tsutsui wrote:
> > abs%NetBSD.org@localhost wrote:
> >>    Both amiga and atari have the concept of 'fast' and 'slow' RAM.
> >>    For a system with a reasonable amount of fast RAM using the
> >>    slow RAM can actually slow things down, though it seems like
> >>    a shame to waste it...
> >
> > I guess ST is on 16 bit bus and TT is on 32 bit bus on atari,
> > and both could be handled by pmap/uvm with proper priorities
> > by MI uvm(9) API. IIRC, mvme68k has some code which handles
> > slower (no cache) VME bus memory.
> 
>       Aha, that would be the free_list param to uvm_page_physload()?
>       Is memory allocated strictly from the freelists in ascending
>       order?

uvm_page_physget() in sys/uvm/uvm_page.c seems to do so.

>       So the 'slow' ram on amiga and atari is probably not 'slow enough'
>       to be worth switching to swap, though it would be beneficial to
>       put them on separate free lists, so fast ram is consumed first?

I think so, but currently atari passes both ST and TT ram to
uvm_page_physload() with the same free_list in pmap_bootstrap.c.

Maybe we could add some parameter which represents ST/TT
in usable_segs[] in atari_init.c.

---
Izumi Tsutsui