Re: [PATCH part2 v2 0/8] Arrange hotpluggable memory as ZONE_MOVABLE

[Zhang Yanfei <zhangyanfei@cn.fujitsu.com>]

ping...

On 11/13/2013 09:50 PM, Zhang Yanfei wrote:
> Hello guys,
> 
> Could anyone help reviewing this part?
> 
> The first part has been merged into linus's tree. And I've tried to apply this part
> to today's linus tree:
> 
> commit 42a2d923cc349583ebf6fdd52a7d35e1c2f7e6bd
> Merge: 5cbb3d2 75ecab1
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Wed Nov 13 17:40:34 2013 +0900
> 
>     Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
> 
> No conflict, no compiling error and it works well.
> 
> Tejun, any comments?
> 
> On 10/12/2013 02:00 PM, Zhang Yanfei wrote:
>> Hello guys, this is the part2 of our memory hotplug work. This part
>> is based on the part1:
>>     "x86, memblock: Allocate memory near kernel image before SRAT parsed"
>> which is base on 3.12-rc4.
>>
>> You could refer part1 from: https://lkml.org/lkml/2013/10/10/644
>>
>> Any comments are welcome! Thanks!
>>
>> [Problem]
>>
>> The current Linux cannot migrate pages used by the kerenl because
>> of the kernel direct mapping. In Linux kernel space, va = pa + PAGE_OFFSET.
>> When the pa is changed, we cannot simply update the pagetable and
>> keep the va unmodified. So the kernel pages are not migratable.
>>
>> There are also some other issues will cause the kernel pages not migratable.
>> For example, the physical address may be cached somewhere and will be used.
>> It is not to update all the caches.
>>
>> When doing memory hotplug in Linux, we first migrate all the pages in one
>> memory device somewhere else, and then remove the device. But if pages are
>> used by the kernel, they are not migratable. As a result, memory used by
>> the kernel cannot be hot-removed.
>>
>> Modifying the kernel direct mapping mechanism is too difficult to do. And
>> it may cause the kernel performance down and unstable. So we use the following
>> way to do memory hotplug.
>>
>>
>> [What we are doing]
>>
>> In Linux, memory in one numa node is divided into several zones. One of the
>> zones is ZONE_MOVABLE, which the kernel won't use.
>>
>> In order to implement memory hotplug in Linux, we are going to arrange all
>> hotpluggable memory in ZONE_MOVABLE so that the kernel won't use these memory.
>>
>> To do this, we need ACPI's help.
>>
>>
>> [How we do this]
>>
>> In ACPI, SRAT(System Resource Affinity Table) contains NUMA info. The memory
>> affinities in SRAT record every memory range in the system, and also, flags
>> specifying if the memory range is hotpluggable.
>> (Please refer to ACPI spec 5.0 5.2.16)
>>
>> With the help of SRAT, we have to do the following two things to achieve our
>> goal:
>>
>> 1. When doing memory hot-add, allow the users arranging hotpluggable as
>>    ZONE_MOVABLE.
>>    (This has been done by the MOVABLE_NODE functionality in Linux.)
>>
>> 2. when the system is booting, prevent bootmem allocator from allocating
>>    hotpluggable memory for the kernel before the memory initialization
>>    finishes.
>>    (This is what we are going to do. See below.)
>>
>>
>> [About this patch-set]
>>
>> In previous part's patches, we have made the kernel allocate memory near
>> kernel image before SRAT parsed to avoid allocating hotpluggable memory
>> for kernel. So this patch-set does the following things:
>>
>> 1. Improve memblock to support flags, which are used to indicate different 
>>    memory type.
>>
>> 2. Mark all hotpluggable memory in memblock.memory[].
>>
>> 3. Make the default memblock allocator skip hotpluggable memory.
>>
>> 4. Improve "movable_node" boot option to have higher priority of movablecore
>>    and kernelcore boot option.
>>
>> Change log v1 -> v2:
>> 1. Rebase this part on the v7 version of part1
>> 2. Fix bug: If movable_node boot option not specified, memblock still
>>    checks hotpluggable memory when allocating memory. 
>>
>> Tang Chen (7):
>>   memblock, numa: Introduce flag into memblock
>>   memblock, mem_hotplug: Introduce MEMBLOCK_HOTPLUG flag to mark
>>     hotpluggable regions
>>   memblock: Make memblock_set_node() support different memblock_type
>>   acpi, numa, mem_hotplug: Mark hotpluggable memory in memblock
>>   acpi, numa, mem_hotplug: Mark all nodes the kernel resides
>>     un-hotpluggable
>>   memblock, mem_hotplug: Make memblock skip hotpluggable regions if
>>     needed
>>   x86, numa, acpi, memory-hotplug: Make movable_node have higher
>>     priority
>>
>> Yasuaki Ishimatsu (1):
>>   x86: get pg_data_t's memory from other node
>>
>>  arch/metag/mm/init.c      |    3 +-
>>  arch/metag/mm/numa.c      |    3 +-
>>  arch/microblaze/mm/init.c |    3 +-
>>  arch/powerpc/mm/mem.c     |    2 +-
>>  arch/powerpc/mm/numa.c    |    8 ++-
>>  arch/sh/kernel/setup.c    |    4 +-
>>  arch/sparc/mm/init_64.c   |    5 +-
>>  arch/x86/mm/init_32.c     |    2 +-
>>  arch/x86/mm/init_64.c     |    2 +-
>>  arch/x86/mm/numa.c        |   63 +++++++++++++++++++++--
>>  arch/x86/mm/srat.c        |    5 ++
>>  include/linux/memblock.h  |   39 ++++++++++++++-
>>  mm/memblock.c             |  123 ++++++++++++++++++++++++++++++++++++++-------
>>  mm/memory_hotplug.c       |    1 +
>>  mm/page_alloc.c           |   28 ++++++++++-
>>  15 files changed, 252 insertions(+), 39 deletions(-)
>>
> 
> 


-- 
Thanks.
Zhang Yanfei

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