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

Zi Yan
2021-05-06T15:42:21Z

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

> From: Zi Yan <ziy@nvidia.com>
>
> 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@redhat.com/
[2] https://lore.kernel.org/linux-mm/20200928175428.4110504-1-zi.yan@sent.com/
[3] https://patchwork.kernel.org/project/linux-nvdimm/cover/156092349300.979959.17603710711957735135.stgit@dwillia2-desk3.amr.corp.intel.com/

>
> 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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