SPARSEMEM memory needs?

[Ard Biesheuvel]

On Tue, 7 Jun 2022 at 13:44, Joakim Tjernlund
<Joakim.Tjernlund at infinera.com> wrote:
>
> On Tue, 2022-06-07 at 12:56 +0200, Arnd Bergmann wrote:
> > On Tue, Jun 7, 2022 at 12:03 PM Ard Biesheuvel <ardb at kernel.org> wrote:
> > > On Tue, 7 Jun 2022 at 11:53, Arnd Bergmann <arnd at arndb.de> wrote:
> > > > 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:
> > > > > > >
> >
>
> SNIP
>
> > > So yes to using less memory in the general case, but intrusive changes
> > > such as the one I proposed are unlikely to be adopted (and the arm64
> > > kernel, unlike the 32-bit one, tries really hard to only have a single
> > > image and a single defconfig)
> >
> > I don't see a configurable section size (possibly under CONFIG_EXPERT)
> > as too intrusive. The arm64 defconfig clearly is clearly required to work on
> > any kind of hardware, but there is enough precedence for Kconfig options
> > that make machine specific trade-offs (e.g. page size and VA size), or that
> > completely disable support for certain SoC platforms.
> >

Sure. But if we introduce such a knob, it will now be the job of
developers working on the MM code to ensure that any changes don't
break this niche configuration.

Perhaps we could put it under CONFIG_EXPERT and make it a best-effort thing?