From: David Hildenbrand <firstname.lastname@example.org>
To: Anshuman Khandual <email@example.com>,
Sudarshan Rajagopalan <firstname.lastname@example.org>,
Subject: Re: [PATCH 1/1] arm64: make section size configurable for memory hotplug
Date: Thu, 7 Jan 2021 13:30:55 +0100 [thread overview]
Message-ID: <email@example.com> (raw)
On 06.01.21 07:11, Anshuman Khandual wrote:
> Hi Sudershan,
> This patch (and the cover letter) does not copy LAKML even though the
> entire change here is arm64 specific. Please do copy all applicable
> mailing lists for a given patch.
> On 1/6/21 6:58 AM, Sudarshan Rajagopalan wrote:
>> Currently on arm64, memory section size is hard-coded to 1GB.
>> Make this configurable if memory-hotplug is enabled, to support
>> more finer granularity for hotplug-able memory.
> Section size has always been decided by the platform. It cannot be a
> configurable option because the user would not know the constraints
> for memory representation on the platform and besides it also cannot
> be trusted.
>> Signed-off-by: Sudarshan Rajagopalan <firstname.lastname@example.org>
>> arch/arm64/Kconfig | 11 +++++++++++
>> arch/arm64/include/asm/sparsemem.h | 4 ++++
>> 2 files changed, 15 insertions(+)
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 6d232837cbee..34124eee65da 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -294,6 +294,17 @@ config ARCH_ENABLE_MEMORY_HOTREMOVE
>> config SMP
>> def_bool y
>> +config HOTPLUG_SIZE_BITS
>> + int "Memory hotplug block size(29 => 512MB 30 => 1GB)"
"Memory hotplug block size" and "HOTPLUG_SIZE_BITS" is confusing. It's
the section size. Please use that terminology.
(if at all, it would have to be "minimum memory hot(un)plug
granularity", but even that is somewhat misleading)
But I agree that letting the user configure it is sub-optimal.
>> + depends on SPARSEMEM
>> + depends on MEMORY_HOTPLUG
>> + range 28 30
> 28 would not work for 64K pages.
@Anshuman, what's your feeling about changing this to 128 MB for 4k/16k
base pages (as we have on x86-64 right now) and 512 MB for 64k as
default for now?
(If we worry about the number of section bits in page->flags, we could
glue it to vmemmap support where that does not matter)
David / dhildenb
next prev parent reply other threads:[~2021-01-07 12:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-06 1:28 [PATCH 0/1] arm64: make section size configurable for memory hotplug Sudarshan Rajagopalan
2021-01-06 1:28 ` [PATCH 1/1] " Sudarshan Rajagopalan
2021-01-06 2:20 ` Randy Dunlap
2021-01-06 6:11 ` Anshuman Khandual
2021-01-07 12:30 ` David Hildenbrand [this message]
2021-01-08 7:02 ` Anshuman Khandual
2021-01-08 15:30 ` David Hildenbrand
2021-01-11 4:17 ` Anshuman Khandual
2021-01-11 10:13 ` David Hildenbrand
2021-01-11 10:26 ` Anshuman Khandual
2021-01-08 1:01 ` Sudarshan Rajagopalan
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