From: David Hildenbrand <david@redhat.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>,
Sudarshan Rajagopalan <sudaraja@codeaurora.org>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.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: <d0e627fd-390f-5915-c218-e2137aef3eb4@redhat.com> (raw)
In-Reply-To: <055b0aca-af60-12ad-cd68-e15440ade64b@arm.com>
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 <sudaraja@codeaurora.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)
"SECTION_SIZE_BITS"
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)
--
Thanks,
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d0e627fd-390f-5915-c218-e2137aef3eb4@redhat.com \
--to=david@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=sudaraja@codeaurora.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).