Date:	Tue, 11 Dec 2012 05:33:20 -0600
From:	Simon Jeons <simon.jeons@...il.com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	jiang.liu@...wei.com, wujianguo@...wei.com, hpa@...or.com,
	akpm@...ux-foundation.org, wency@...fujitsu.com,
	laijs@...fujitsu.com, linfeng@...fujitsu.com, yinghai@...nel.org,
	isimatu.yasuaki@...fujitsu.com, rob@...dley.net,
	kosaki.motohiro@...fujitsu.com, minchan.kim@...il.com,
	mgorman@...e.de, rientjes@...gle.com, rusty@...tcorp.com.au,
	lliubbo@...il.com, jaegeuk.hanse@...il.com, tony.luck@...el.com,
	glommer@...allels.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 0/5] Add movablecore_map boot option

On Tue, 2012-12-11 at 10:33 +0800, Tang Chen 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.
> 
> 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.

Could you explain which part of your codes implement point 1 and point
2?

> 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.
> 
> 
> Change log:
> 
> v2 -> v3:
> 1) Use memblock_alloc_try_nid() instead of memblock_alloc_nid() to allocate
>    memory twice if a whole node is ZONE_MOVABLE.
> 2) Add DMA, DMA32 addresses check, make sure ZONE_MOVABLE won't use these addresses.
>    Suggested by Wu Jianguo <wujianguo@...wei.com>
> 3) Add lowmem addresses check, when the system has highmem, make sure ZONE_MOVABLE
>    won't use lowmem. Suggested by Liu Jiang <jiang.liu@...wei.com>
> 4) Fix misuse of pfns in movablecore_map.map[] as physical addresses.
> 
> 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                  |    5 +-
>  include/linux/memblock.h            |    1 +
>  include/linux/mm.h                  |   11 ++
>  mm/memblock.c                       |   18 +++-
>  mm/page_alloc.c                     |  238 ++++++++++++++++++++++++++++++++++-
>  6 files changed, 282 insertions(+), 8 deletions(-)
> 
> --
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