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

[Zhang Yanfei <zhangyanfei.yes@gmail.com>]

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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