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

[Dan Williams]

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.

It's only ridiculous due to what it does to /sys/.../memory,
right?

If you permit me a bit of hand-waving, it would be lovely to deprecate
/sys/.../memory in favor of a new (fd based?) ABI for memory-hotplug
policy management and have something like a fuse "compatfs" mounted at
/sys/.../memory/ for maintaining legacy compatibility for userspace that
still depends on twiddling with individual blocks in sysfs.