Re: [PATCH v6 00/12] mm: Sub-section memory hotplug support

[Jeff Moyer]

Dan Williams <dan.j.williams@xxxxxxxxx> writes:

>> 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.

Sure.  I'll also have a look over the patches.

-Jeff