From: Dan Williams <dan.j.williams@intel.com>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
Logan Gunthorpe <logang@deltatee.com>,
Linux MM <linux-mm@kvack.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v6 01/12] mm/sparsemem: Introduce struct mem_section_usage
Date: Wed, 1 May 2019 23:07:21 -0700 [thread overview]
Message-ID: <CAPcyv4hxy86gWN3ncTQmHi8DT31k8YzsweMfGHgCh=sORMQQcg@mail.gmail.com> (raw)
In-Reply-To: <20190501232517.crbmgcuk7u4gvujr@soleen.tm1wkky2jk1uhgkn0ivaxijq1c.bx.internal.cloudapp.net>
On Wed, May 1, 2019 at 4:25 PM Pavel Tatashin <pasha.tatashin@soleen.com> wrote:
>
> On 19-04-17 11:39:00, Dan Williams wrote:
> > Towards enabling memory hotplug to track partial population of a
> > section, introduce 'struct mem_section_usage'.
> >
> > A pointer to a 'struct mem_section_usage' instance replaces the existing
> > pointer to a 'pageblock_flags' bitmap. Effectively it adds one more
> > 'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to
> > house a new 'map_active' bitmap. The new bitmap enables the memory
> > hot{plug,remove} implementation to act on incremental sub-divisions of a
> > section.
> >
> > The primary motivation for this functionality is to support platforms
> > that mix "System RAM" and "Persistent Memory" within a single section,
> > or multiple PMEM ranges with different mapping lifetimes within a single
> > section. The section restriction for hotplug has caused an ongoing saga
> > of hacks and bugs for devm_memremap_pages() users.
> >
> > Beyond the fixups to teach existing paths how to retrieve the 'usemap'
> > from a section, and updates to usemap allocation path, there are no
> > expected behavior changes.
> >
> > Cc: Michal Hocko <mhocko@suse.com>
> > Cc: Vlastimil Babka <vbabka@suse.cz>
> > Cc: Logan Gunthorpe <logang@deltatee.com>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> > include/linux/mmzone.h | 23 ++++++++++++--
> > mm/memory_hotplug.c | 18 ++++++-----
> > mm/page_alloc.c | 2 +
> > mm/sparse.c | 81 ++++++++++++++++++++++++------------------------
> > 4 files changed, 71 insertions(+), 53 deletions(-)
> >
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 70394cabaf4e..f0bbd85dc19a 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -1160,6 +1160,19 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
> > #define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
> > #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK)
> >
> > +#define SECTION_ACTIVE_SIZE ((1UL << SECTION_SIZE_BITS) / BITS_PER_LONG)
> > +#define SECTION_ACTIVE_MASK (~(SECTION_ACTIVE_SIZE - 1))
> > +
> > +struct mem_section_usage {
> > + /*
> > + * SECTION_ACTIVE_SIZE portions of the section that are populated in
> > + * the memmap
> > + */
> > + unsigned long map_active;
>
> I think this should be proportional to section_size / subsection_size.
> For example, on intel section size = 128M, and subsection is 2M, so
> 64bits work nicely. But, on arm64 section size if 1G, so subsection is
> 16M.
>
> On the other hand 16M is already much better than what we have: with 1G
> section size and 2M pmem alignment we guaranteed to loose 1022M. And
> with 16M subsection it is only 14M.
I'm ok with it being 16M for now unless it causes a problem in
practice, i.e. something like the minimum hardware mapping alignment
for physical memory being less than 16M.
next prev parent reply other threads:[~2019-05-02 6:07 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-17 18:38 [PATCH v6 00/12] mm: Sub-section memory hotplug support Dan Williams
2019-04-17 18:39 ` [PATCH v6 01/12] mm/sparsemem: Introduce struct mem_section_usage Dan Williams
2019-05-01 23:25 ` Pavel Tatashin
2019-05-02 6:07 ` Dan Williams [this message]
2019-05-02 14:16 ` Pavel Tatashin
2019-05-04 0:22 ` Dan Williams
2019-05-04 15:55 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 02/12] mm/sparsemem: Introduce common definitions for the size and mask of a section Dan Williams
2019-05-02 14:53 ` Pavel Tatashin
2019-05-03 0:41 ` Dan Williams
2019-05-03 10:35 ` Robin Murphy
2019-05-03 12:57 ` Pavel Tatashin
2019-05-03 13:00 ` Oscar Salvador
2019-04-17 18:39 ` [PATCH v6 03/12] mm/sparsemem: Add helpers track active portions of a section at boot Dan Williams
2019-04-25 14:33 ` Oscar Salvador
2019-04-25 14:43 ` Oscar Salvador
2019-04-26 12:57 ` Oscar Salvador
2019-05-02 16:12 ` Pavel Tatashin
2019-05-04 19:26 ` Dan Williams
2019-04-17 18:39 ` [PATCH v6 04/12] mm/hotplug: Prepare shrink_{zone, pgdat}_span for sub-section removal Dan Williams
2019-04-19 23:09 ` Ralph Campbell
2019-04-19 23:13 ` Dan Williams
2019-04-26 13:59 ` Oscar Salvador
2019-04-26 14:00 ` Oscar Salvador
2019-05-02 19:18 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 05/12] mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap() Dan Williams
2019-05-02 19:28 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 06/12] mm/hotplug: Add mem-hotplug restrictions for remove_memory() Dan Williams
2019-04-23 21:21 ` David Hildenbrand
2019-04-24 18:07 ` Dan Williams
2019-04-17 18:39 ` [PATCH v6 07/12] mm: Kill is_dev_zone() helper Dan Williams
2019-04-17 20:17 ` David Hildenbrand
2019-04-26 14:04 ` Oscar Salvador
2019-05-02 20:37 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 08/12] mm/sparsemem: Prepare for sub-section ranges Dan Williams
2019-05-02 21:25 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 09/12] mm/sparsemem: Support sub-section hotplug Dan Williams
2019-04-17 18:39 ` [PATCH v6 10/12] mm/devm_memremap_pages: Enable sub-section remap Dan Williams
2019-04-17 18:39 ` [PATCH v6 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields Dan Williams
2019-04-17 22:02 ` Andrew Morton
2019-04-17 22:09 ` Dan Williams
2019-04-17 18:39 ` [PATCH v6 12/12] libnvdimm/pfn: Stop padding pmem namespaces to section alignment Dan Williams
2019-04-17 22:03 ` [PATCH v6 00/12] mm: Sub-section memory hotplug support Andrew Morton
2019-04-17 22:59 ` Dan Williams
2019-04-18 2:09 ` Dan Williams
2019-04-18 12:45 ` Jeff Moyer
2019-04-19 3:25 ` Dan Williams
2019-04-23 13:16 ` Oscar Salvador
2019-04-24 20:43 ` Pavel Tatashin
2019-05-02 22:46 ` Pavel Tatashin
2019-05-02 23:20 ` Dan Williams
2019-05-02 23:21 ` Dan Williams
2019-05-03 10:48 ` Oscar Salvador
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