Subject: Number of NKMEMPAGES?
To: None <>
From: John <>
List: port-m68k
Date: 06/04/2001 16:58:19

I posted this to tech-kern and port-amiga, but now I think this might be
most appropriate in port-m68k.

What I really would like to know is whether the MMU in the m68k is so
different from that of i386 or PowerPC that the number of NKMEMPAGES
should be significantly different between m68k and (i386, ppc, Alpha).

Should this be considered on all m68k ports that have a very modest amount
of NKMEMPAGES? The breakdown:

Amiga:		384 (8k)
Atari:		384 (8k)
hp300:		1536 to 2048 (4k)
luna68k		768 (4k)
mac68k:		768 (4k)
mvme68k:	1024 to 1536 (4k)
news68k:	1024 (4k)
next68k:	1024 (4k)
sun3:		384 (8k)
x68k:		768 to 1024 (4k)

Compare this to PowerPC, Alpha, and i386 (up to 32768); are they really
THAT different?

With memory as cheap as it is, I have most of my m68k machines maxed out -
I have several Quadras with 136 megs, three Amigas with 144 megs, one
Amiga with 256. I even have 104 megs in my VAX (1024 pages, 4k sized pages)

If this doesn't get changed in the sources, then could someone at least
tell me what a good guideline might be?

The original post:

I've looked into the default values for NKMEMPAGES for all of the
architectures NetBSD supports, and I'm a little puzzled. According to the
comments in the code, the number of NKMEMPAGES is calculated by physical
ram size times some machine dependent code.

Looking at i386 machines, this is true: a machine with 192 megs of memory
has 12260 vm.nkmempages; a machine with 256 megs has 16280.

But Amigas have 384 always, whether 16 or 256 megs.

Is there something fundamentally different about the MMUs in m68k and
i386? If there isn't, then shouldn't
be increased in sys/arch/amiga/include/param.h?

Finally, should I assume that my 128 meg Amiga should have 4000 NKMEMPAGES
(i386 has 8000 for 128 meg with 4k pages; Amiga uses 8k pages).

Thanks very much,
John Klos
The proof of a system's value is its existence.