Re: [PATCHv3 2/4] x86/64/mm: Make SPARSEMEM_VMEMMAP the only memory model

[Ingo Molnar]

* Dave Hansen <dave.hansen@xxxxxxxxx> wrote:

> On 5/16/25 07:08, Ingo Molnar wrote:
> >> And is there any value to support !SPARSEMEM_VMEMMAP?
> > Not really IMHO:
> > 
> >   .config.opensuse.default:    CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
> >   .config.ubuntu.localinstall: CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
> >   .config.fedora.generic:      CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
> >   .config.rhel.generic:        CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
> 
> I look at the distro configs all the time as well.
> 
> But let's also not forget that none of these have lockdep turned on,

Not actually true, quite a few distro debug kernel packages have 
lockdep on, and it's often enabled in internal QA rigs as well.

Not so SPARSEMEM_VMEMMAP...

> [...] and we don't want to toss out lockdep support on x86, for 
> example. ;)

That's an apples to oranges comparison:

 - SPARSEMEM_VMEMMAP is always enabled, in standard and debug kernels 
   as well.

 - lockdep is disabled in standard kernels, enabled in debug kernels 
   and very much relied on.

Thanks,

	Ingo