SPARSEMEM memory needs?

[Arnd Bergmann]

On Tue, Jun 7, 2022 at 11:38 AM Ard Biesheuvel <ardb at kernel.org> wrote:
> On Tue, 7 Jun 2022 at 11:29, Joakim Tjernlund <Joakim.Tjernlund at infinera.com> wrote:
> > >
> > > OK, so even if I am not a fan of this practice [0], running a 32-bit
> > > kernel would likely be an option for you as well. Have you considered
> > > this?
> > >
> ..
> >
> > Briefly considered 32 bits kernel but as I understand it, it is even more unsupported so I have opted
> > for 64 bits kernel for now. I may have to revisit that though. ARM is still new to me.
>
> It is a bad idea for many reasons, but you may not have a choice.

They are clearly both bad on this hardware ;-)

If we can improve support for a 36MB configuration on arm64, that
would likely also help
those users with actual DDR3 ram (128MB to 512MB typically) that you see more
commonly, and that's certainly a good thing.

Another alternative to using a 32-bit kernel would be to not use Linux
at all. There are
enough RTOS variants in the world that have a growing feature set and that may
be sufficient for Joakim's workload but use a lot less RAM.
If there is only one application running, there may not be a no need
for the complexity
in our file systems, memory protection or network stack either.

        Arnd