linux-kernel - Re: [PATCH v2 0/5] Add movablecore

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Message-ID: <CAA_GA1d7CxHvmZELvD_DO6u5tu1WBqfmLiuEzeFo=xMzuW50Tg@mail.gmail.com>
Date:	Tue, 27 Nov 2012 16:00:56 +0800
From:	Bob Liu <lliubbo@...il.com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	hpa@...or.com, akpm@...ux-foundation.org, rob@...dley.net,
	isimatu.yasuaki@...fujitsu.com, laijs@...fujitsu.com,
	wency@...fujitsu.com, linfeng@...fujitsu.com, jiang.liu@...wei.com,
	yinghai@...nel.org, kosaki.motohiro@...fujitsu.com,
	minchan.kim@...il.com, mgorman@...e.de, rientjes@...gle.com,
	rusty@...tcorp.com.au, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 0/5] Add movablecore_map boot option

Hi Tang,

On Fri, Nov 23, 2012 at 6:44 PM, Tang Chen <tangchen@...fujitsu.com> wrote:
> [What we are doing]
> This patchset provide a boot option for user to specify ZONE_MOVABLE memory
> map for each node in the system.
>
> movablecore_map=nn[KMG]@ss[KMG]
>
> This option make sure memory range from ss to ss+nn is movable memory.
>
>
> [Why we do this]
> If we hot remove a memroy, the memory cannot have kernel memory,
> because Linux cannot migrate kernel memory currently. Therefore,
> we have to guarantee that the hot removed memory has only movable
> memoroy.
>
> Linux has two boot options, kernelcore= and movablecore=, for
> creating movable memory. These boot options can specify the amount
> of memory use as kernel or movable memory. Using them, we can
> create ZONE_MOVABLE which has only movable memory.
>
> But it does not fulfill a requirement of memory hot remove, because
> even if we specify the boot options, movable memory is distributed
> in each node evenly. So when we want to hot remove memory which
> memory range is 0x80000000-0c0000000, we have no way to specify
> the memory as movable memory.
>

Sorry, I'm still not get your idea.
Why you need a specify range that is movable?
Could you describe the requirement and situation a bit more?
Thank you.

> So we proposed a new feature which specifies memory range to use as
> movable memory.
>
>
> [Ways to do this]
> There may be 2 ways to specify movable memory.
>  1. use firmware information
>  2. use boot option
>
> 1. use firmware information
>   According to ACPI spec 5.0, SRAT table has memory affinity structure
>   and the structure has Hot Pluggable Filed. See "5.2.16.2 Memory
>   Affinity Structure". If we use the information, we might be able to
>   specify movable memory by firmware. For example, if Hot Pluggable
>   Filed is enabled, Linux sets the memory as movable memory.
>
> 2. use boot option
>   This is our proposal. New boot option can specify memory range to use
>   as movable memory.
>
>
> [How we do this]
> We chose second way, because if we use first way, users cannot change
> memory range to use as movable memory easily. We think if we create
> movable memory, performance regression may occur by NUMA. In this case,
> user can turn off the feature easily if we prepare the boot option.
> And if we prepare the boot optino, the user can select which memory
> to use as movable memory easily.
>
>
> [How to use]
> Specify the following boot option:
> movablecore_map=nn[KMG]@ss[KMG]
>
> That means physical address range from ss to ss+nn will be allocated as
> ZONE_MOVABLE.
>
> And the following points should be considered.
>
> 1) If the range is involved in a single node, then from ss to the end of
>    the node will be ZONE_MOVABLE.
> 2) If the range covers two or more nodes, then from ss to the end of
>    the node will be ZONE_MOVABLE, and all the other nodes will only
>    have ZONE_MOVABLE.
> 3) If no range is in the node, then the node will have no ZONE_MOVABLE
>    unless kernelcore or movablecore is specified.
> 4) This option could be specified at most MAX_NUMNODES times.
> 5) If kernelcore or movablecore is also specified, movablecore_map will have
>    higher priority to be satisfied.
> 6) This option has no conflict with memmap option.
>
>
>
> Tang Chen (4):
>   page_alloc: add movable_memmap kernel parameter
>   page_alloc: Introduce zone_movable_limit[] to keep movable limit for
>     nodes
>   page_alloc: Make movablecore_map has higher priority
>   page_alloc: Bootmem limit with movablecore_map
>
> Yasuaki Ishimatsu (1):
>   x86: get pg_data_t's memory from other node
>
>  Documentation/kernel-parameters.txt |   17 +++
>  arch/x86/mm/numa.c                  |   11 ++-
>  include/linux/memblock.h            |    1 +
>  include/linux/mm.h                  |   11 ++
>  mm/memblock.c                       |   15 +++-
>  mm/page_alloc.c                     |  216 ++++++++++++++++++++++++++++++++++-
>  6 files changed, 263 insertions(+), 8 deletions(-)
>
> --
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-- 
Regards,
-Bob
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