linux-kernel - [PATCH 0/1] arm64: make section size configurable for memory hotplug

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Date:   Tue,  5 Jan 2021 17:28:45 -0800
From:   Sudarshan Rajagopalan <sudaraja@...eaurora.org>
To:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Sudarshan Rajagopalan <sudaraja@...eaurora.org>
Subject: [PATCH 0/1] arm64: make section size configurable for memory hotplug

The section size defines the granularity of memory hotplug. This is currently
hard coded to 1GB on arm64 linux, which defines that the least size of memblock
that can be hotplugged out is 1GB. Some DDR configurations (especially low RAM
and dual-rank DDRs) may have section sizes that are less than 1GB (ex. 512MB, 256MB etc.).
Having an option to reduce the memblock size to section size or lower gives more
granularity of memory hotplug. For example, a system with DDR section size of 512MB
and kernel memblock size of 1GB, we would have to remove two segments of DDR sections
in order to hotplug out atleast 1 memblock from kernel POV. 

Section sizes of DDRs vary based on specs (number of ranks, channels, regions etc.)
Making this section size configurable helps users to assign based on the DDR being used.
The default is set to 1GB which is the current memblock size.

Sudarshan Rajagopalan (1):
  arm64: Make section size configurable for memory hotplug

 arch/arm64/Kconfig                 | 11 +++++++++++
 arch/arm64/include/asm/sparsemem.h |  4 ++++
 2 files changed, 15 insertions(+)

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