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

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Date:   Wed, 24 Apr 2019 16:43:35 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Toshi Kani <toshi.kani@....com>,
        Jeff Moyer <jmoyer@...hat.com>, Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        stable <stable@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 00/12] mm: Sub-section memory hotplug support

I am also taking a look at this work now. I will review and test it in
the next couple of days.

Pasha

On Tue, Apr 23, 2019 at 9:17 AM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Wed, 2019-04-17 at 15:59 -0700, Dan Williams wrote:
> > On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@...ux-foundation.
> > org> wrote:
> > >
> > > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@int
> > > el.com> 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.
>
> Thanks Dan for ccing me.
> I will take a look at the patches soon.
>
> --
> Oscar Salvador
> SUSE L3