Re: [PATCH v8 0/3] memory,x86,acpi: hotplug memory alignment advisement

[David Hildenbrand]

On 01.04.25 20:53, Oscar Salvador wrote:
> On Mon, Jan 27, 2025 at 10:34:02AM -0500, Gregory Price wrote:
> > v8: nits and tag pickups
> >
> > When physical address regions are not aligned to memory block size,
> > the misaligned portion is lost (stranded capacity).
> >
> > Block size (min/max/selected) is architecture defined. Most architectures
> > tend to use the minimum block size or some simplistic heurist. On x86,
> > memory block size increases up to 2GB, and is otherwise fitted to the
> > alignment of non-hotplug (i.e. not special purpose memory).
>
> I wonder if something like this could help us in improving the
> ridiculous situation of having 16MB memory-block size on powerpc.

They have this granularity because ... they want to add/remove memory in 
16MiB on some powerpc dlpar machines :(

probe_memory_block_size() can query the hypervisor on the actual 
hot(un)plug size. IIRC, QEMU sets it to 256 MiB.

--
Cheers,

David / dhildenb