On Wed, Apr 17, 2019 at 3:59 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> >
> > > The memory hotplug section is an arbitrary / convenient unit for memory
> > > hotplug. 'Section-size' units have bled into the user interface
> > > ('memblock' sysfs) and can not be changed without breaking existing
> > > userspace. The section-size constraint, while mostly benign for typical
> > > memory hotplug, has and continues to wreak havoc with 'device-memory'
> > > use cases, persistent memory (pmem) in particular. Recall that pmem uses
> > > devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a
> > > 'struct page' memmap for pmem. However, it does not use the 'bottom
> > > half' of memory hotplug, i.e. never marks pmem pages online and never
> > > exposes the userspace memblock interface for pmem. This leaves an
> > > opening to redress the section-size constraint.
> >
> > v6 and we're not showing any review activity. Who would be suitable
> > people to help out here?
>
> There was quite a bit of review of the cover letter from Michal and
> David, but you're right the details not so much as of yet. I'd like to
> call out other people where I can reciprocate with some review of my
> own. Oscar's altmap work looks like a good candidate for that.
I'm also hoping Jeff can give a tested-by for the customer scenarios
that fall over with the current implementation.
