Re: Question on BIGGEST_ALIGNMENT in GCC on NetBSD/m68k

Hi,

On 11.6.2025 10.44, John Paul Adrian Glaubitz wrote:
> As previously stated, NetBSD uses 4 bytes alignment and runs fine even on
> 68010-based systems. In fact, using a 4 bytes alignment will actually
> improve performance as it's the natural alignment the hardware uses.

It will decrease performance if increased alignment means that something 
that fit earlier into i/d-cache, does not fit any more.

(68030 has 256 bytes, 68040 has 4 KB, and 68060 has 8 KB, of both.)

To get some numbers on this...

if you could provide vmlinuz & System.map files for both (otherwise 
identical) 2-byte & 4-byte alignment kernel builds, using kernel config 
here:
https://github.com/hatari/hatari/blob/main/tools/linux/kernel.config

I could measure the perf difference for the whole kernel boot, and if 
there are differences, profile what causes those differences.


	- Eero

PS. I will be using Hatari for that, as it has semi-cycle-accurate 
emulation for 38030, and good profiling facilities: 
https://www.hatari-emu.org/doc/debugger.html#Profiling)