On Tue, 18 Feb 2020 11:05:32 +0100 Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> Subject: [PATCH] memory_hotplug: disable the functionality for 32b
>
> Memory hotlug is broken for 32b systems at least since c6f03e2903c9
> ("mm, memory_hotplug: remove zone restrictions") which has considerably
> reworked how can be memory associated with movable/kernel zones. The
> same is not really trivial to achieve in 32b where only lowmem is the
> kernel zone. While we can tweak this immediate problem around there are
> likely other land mines hidden at other places.
>
> It is also quite dubious that there is a real usecase for the memory
> hotplug on 32b in the first place. Low memory is just too small to be
> hotplugable (for hot add) and generally unusable for hotremove. Adding
> more memory to highmem is also dubious because it would increase the
> low mem or vmalloc space pressure for memmaps.
>
> Restrict the functionality to 64b systems. This will help future
> development to focus on usecases that have real life application. We
> can remove this restriction in future in presence of a real life usecase
> of course but until then make it explicit that hotplug on 32b is broken
> and requires a non trivial amount of work to fix.
(cc linux-arch)
(and linux-arm-kernel, as ARM is a major 32-bit user)
Does anyone see a problem with disabling memory hotplug on 32-bit builds?
