SPARSEMEM memory needs?

[Arnd Bergmann]

On Tue, Jun 7, 2022 at 8:36 AM Joakim Tjernlund
<Joakim.Tjernlund at infinera.com> wrote:
> On Mon, 2022-06-06 at 23:50 +0200, Ard Biesheuvel wrote:
> > So the problem is that you only have 36 MB of DRAM, with a large hole
> > in the middle. Sparsemem was actually designed for that (hence the
> > name), and flatmem would make things much worse.
>
> Yes, that hole is not ideal.

Is there a reason for this hole? Are both sections actually required to be
normal RAM, rather than something else? If the 4MB chunk is actually
some fast SRAM, then having a special-purpose device driver or an XIP
capable file system for it would let you some critical data on it and not
actually require page pointers.

        Arnd