Re: [RFC PATCH 0/7] Memory hotplug/hotremove at subsection size

[Zi Yan]

On 6 May 2021, at 11:26, Zi Yan wrote:

> From: Zi Yan <ziy@xxxxxxxxxx>
>
> Hi all,
>
> This patchset tries to remove the restriction on memory hotplug/hotremove
> granularity, which is always greater or equal to memory section size[1].
> With the patchset, kernel is able to online/offline memory at a size independent
> of memory section size, as small as 2MB (the subsection size).
>
> The motivation is to increase MAX_ORDER of the buddy allocator and pageblock
> size without increasing memory hotplug/hotremove granularity at the same time,
> so that the kernel can allocator 1GB pages using buddy allocator and utilizes
> existing pageblock based anti-fragmentation, paving the road for 1GB THP
> support[2].
>
> The patchset utilizes the existing subsection support[3] and changes the
> section size alignment checks to subsection size alignment checks. There are
> also changes to pageblock code to support partial pageblocks, when pageblock
> size is increased along with MAX_ORDER. Increasing pageblock size can enable
> kernel to utilize existing anti-fragmentation mechanism for gigantic page
> allocations.
>
> The last patch increases SECTION_SIZE_BITS to demonstrate the use of memory
> hotplug/hotremove subsection, but is not intended to be merged as is. It is
> there in case one wants to try this out and will be removed during the final
> submission.
>
> Feel free to give suggestions and comments. I am looking forward to your
> feedback.
>
> Thanks.

Added the missing references.

[1] https://lore.kernel.org/linux-mm/4b3006cf-3391-6839-904e-b415613198cb@xxxxxxxxxx/
[2] https://lore.kernel.org/linux-mm/20200928175428.4110504-1-zi.yan@xxxxxxxx/
[3] https://patchwork.kernel.org/project/linux-nvdimm/cover/156092349300.979959.17603710711957735135.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

>
> Zi Yan (7):
>   mm: sparse: set/clear subsection bitmap when pages are
>     onlined/offlined.
>   mm: set pageblock_order to the max of HUGETLB_PAGE_ORDER and
>     MAX_ORDER-1
>   mm: memory_hotplug: decouple memory_block size with section size.
>   mm: pageblock: allow set/unset migratetype for partial pageblock
>   mm: memory_hotplug, sparse: enable memory hotplug/hotremove
>     subsections
>   arch: x86: no MAX_ORDER exceeds SECTION_SIZE check for 32bit vdso.
>   [not for merge] mm: increase SECTION_SIZE_BITS to 31
>
>  arch/ia64/Kconfig                |   1 -
>  arch/powerpc/Kconfig             |   1 -
>  arch/x86/Kconfig                 |  15 +++
>  arch/x86/entry/vdso/Makefile     |   1 +
>  arch/x86/include/asm/sparsemem.h |   2 +-
>  drivers/base/memory.c            | 176 +++++++++++++++----------------
>  drivers/base/node.c              |   2 +-
>  include/linux/memory.h           |   8 +-
>  include/linux/mmzone.h           |   2 +
>  include/linux/page-isolation.h   |   8 +-
>  include/linux/pageblock-flags.h  |   9 --
>  mm/Kconfig                       |   7 --
>  mm/memory_hotplug.c              |  22 ++--
>  mm/page_alloc.c                  |  40 ++++---
>  mm/page_isolation.c              |  30 +++---
>  mm/sparse.c                      |  55 ++++++++--
>  16 files changed, 219 insertions(+), 160 deletions(-)
>
> -- 
> 2.30.2


—
Best Regards,
Yan Zi

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