Re: Kernel tweaks on TT030

[David Brownlee <abs%netbsd.org@localhost>]

2009/11/20 David Ross <dross%pobox.com@localhost>:
>
>
> It looks like we don't need "options FPU_EMULATE" in the ATARITT kernel 
> configuration file.
> http://mail-index.netbsd.org/port-atari/2000/01/31/0001.html
>
> I tried commenting out that option and I now have a smaller kernel. Â=) ÂIt 
> boots and seems to work. Âdmesg still says:
>
> Atari TT (m68030 CPU/MMU mc68882 FPU)
>
> Since no TT030 shipped without an FPU, we should probably make this change 
> permanently in /usr/src/sys/arch/atari/conf/ATARITT.
>
> Questions:
> Â- What's something I can try quickly that would exercise the FPU, just to 
> test?

'ping -c 2 localhost' should be a good test (it uses floating point
for its final summary line), though generally *something* will
coredump during the boot sequence if floating point is broken. If you
want to confirm I'll update the ATARITT kernel config.

> Â- Would it also make sense to move kernel compilation from using -m68020 to 
> -m68030?

That should already be happening,Makefile.atari includes
sys/arch/m68k/Makefile.cmachflags which sets the compile flags
automatically based on which of M680[2346]0 are defined.

> Â- How about moving from -O2 to -O3?

In general the size/speed tradeoffs in -O3 are not worthwhile. They
are a benefit in some cases, but it really involves testing before
just turning them on. Actually given the memory constraints of most
NetBSD/atari machines it might be better to compile '-O2 -Os'

> Â- Anything else we might be able to tweak for a "free" performance gain?

Well, TANSTAAFL :), but dropping FPU_EMULATE should definitely gain
memory, and I'd be curious as to some benchmarks for a kernel compiled
-O2 vs '-O2 -Os' :)

Actually, if you have a moment could you test booting
http://mono.org/abs/atari/netbsd-tt-wskbd.bz2
and see if it attaches a wskbd, and does the keyboard still work? :)