From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
Baoquan He <bhe@redhat.com>
Subject: Re: [PATCH v3 6/6] mm: document semantics of ZONE_MOVABLE
Date: Tue, 4 Aug 2020 13:03:33 +0300 [thread overview]
Message-ID: <20200804100333.GC8243@kernel.org> (raw)
In-Reply-To: <65deeb21-63fe-d1c1-bb87-74a08035f79a@redhat.com>
On Tue, Aug 04, 2020 at 11:55:10AM +0200, David Hildenbrand wrote:
> On 04.08.20 11:33, Mike Rapoport wrote:
> > On Tue, Aug 04, 2020 at 09:24:08AM +0200, David Hildenbrand wrote:
> >> Let's document what ZONE_MOVABLE means, how it's used, and which special
> >> cases we have regarding unmovable pages (memory offlining vs. migration /
> >> allocations).
> >>
> >> Cc: Andrew Morton <akpm@linux-foundation.org>
> >> Cc: Michal Hocko <mhocko@suse.com>
> >> Cc: Michael S. Tsirkin <mst@redhat.com>
> >> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> >> Cc: Mike Rapoport <rppt@kernel.org>
> >> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> >> Cc: Baoquan He <bhe@redhat.com>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> >
> > Several nits below, othersize
> >
> > Acked-by: Mike Rapoport <rppt@linux.ibm.com>
> >
> >> ---
> >> include/linux/mmzone.h | 34 ++++++++++++++++++++++++++++++++++
> >> 1 file changed, 34 insertions(+)
> >>
> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> >> index f6f884970511d..600d449e7d9e9 100644
> >> --- a/include/linux/mmzone.h
> >> +++ b/include/linux/mmzone.h
> >> @@ -372,6 +372,40 @@ enum zone_type {
> >> */
> >> ZONE_HIGHMEM,
> >> #endif
> >> + /*
> >> + * ZONE_MOVABLE is similar to ZONE_NORMAL, except that it *primarily*
> >> + * only contains movable pages. Main use cases are to make memory
> >
> > "Primarily only" sounds awkward. Maybe
> >
> > ... except that it only contains movable pages with few exceptional
> > cases described below.
> >
> > And then
> >
> > Main use cases for ZONE_MOVABLE are ...
>
> Ack!
>
> >
> >> + * offlining more likely to succeed, and to locally limit unmovable
> >> + * allocations - e.g., to increase the number of THP/huge pages.
> >> + * Notable special cases are:
> >> + *
> >> + * 1. Pinned pages: (Long-term) pinning of movable pages might
> >
> > ^long, capital L looked out of place for me
>
> Ack!
>
> >
> >> + * essentially turn such pages unmovable. Memory offlining might
> >> + * retry a long time.
> >> + * 2. memblock allocations: kernelcore/movablecore setups might create
> >> + * situations where ZONE_MOVABLE contains unmovable allocations
> >> + * after boot. Memory offlining and allocations fail early.
> >> + * 3. Memory holes: Such pages cannot be allocated. Applies only to
> >> + * boot memory, not hotplugged memory. Memory offlining and
> >> + * allocations fail early.
> >
> > I would clarify where page struct for abscent memory come from
>
> Something like:
>
> Memory holes: We might have a memmap for memory holes, for example, if
^w ;-)
> we have sections that are only partially System RAM. Such pages cannot
> be ...
How about
... sections that are only partially populated
?
> ?
>
> Thanks!
>
> --
> Thanks,
>
> David / dhildenb
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-08-04 10:03 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-04 7:24 [PATCH v3 0/6] mm / virtio-mem: support ZONE_MOVABLE David Hildenbrand
2020-08-04 7:24 ` [PATCH v3 1/6] mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate() David Hildenbrand
2020-08-04 7:24 ` [PATCH v3 2/6] mm/page_alloc: tweak comments in has_unmovable_pages() David Hildenbrand
2020-08-04 7:24 ` [PATCH v3 3/6] mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate() David Hildenbrand
2020-08-04 7:24 ` [PATCH v3 4/6] mm/page_isolation: cleanup set_migratetype_isolate() David Hildenbrand
2020-08-04 7:24 ` [PATCH v3 5/6] virtio-mem: don't special-case ZONE_MOVABLE David Hildenbrand
2020-08-04 7:24 ` [PATCH v3 6/6] mm: document semantics of ZONE_MOVABLE David Hildenbrand
2020-08-04 9:33 ` Mike Rapoport
2020-08-04 9:55 ` David Hildenbrand
2020-08-04 10:03 ` Mike Rapoport [this message]
2020-08-04 10:04 ` David Hildenbrand
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