Re: [PATCH] mm: nommu: point to the write iterator upon split_vma

[Geert Uytterhoeven]

Hi Andrew,

On Mon, 6 Jul 2026 at 07:23, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 6 Jul 2026 04:58:28 +0100 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> > On Sun, Jul 05, 2026 at 03:27:08PM -0700, Andrew Morton wrote:
> > > Thanks.  Unfortunately we aren't very diligent about the nommu code
> > > (are we?).   Perhaps appropriately - clearly this code doesn't get used a
> > > lot.
> >
> > Should we delete support for NOMMU?  As you say, it doesn't get much
> > testing, or presumably usage.  I have this quote from #m68k a couple of
> > years ago...
>
> Greg is busily developing kernel code.
>
> > : I looked at nommu very briefly when I had my 68000 board on the bench
> > : but didn’t get anywhere. Also didn’t try particularly hard. I think
> > : you are better off with fuzix or OS9 if you want something unixy.
> >
> > (i suspect Zephyr would also be good, but it doesn't support m68k, just
> > arc, arm, arm64, mips, openrisc, renesas rx, riscv, sparc, x86 and xtensa)
>
> Greg, how mush use is NOMMU Linux seeing nowadays?

Nommu (SH-compatible J-Core ASIC) is used in actual products, running
modern kernels.  The rationale is low interrupt latency without using
a much more costly app CPU core + RT CPU core split.

Please watch the recording of the "32bit and-or noMMU Linux BoF"[1]
at LPC2025 for more info.

[1] https://lpc.events/event/19/contributions/2097/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds