Re: [Part3 PATCH v2 0/4] Support hot-remove local pagetable pages.

[Jianguo Wu <wujianguo@huawei.com>]

Hi Tang,

On 2013/6/13 21:03, Tang Chen wrote:

> The following patch-set from Yinghai allocates pagetables to local nodes.
> v1: https://lkml.org/lkml/2013/3/7/642
> v2: https://lkml.org/lkml/2013/3/10/47
> v3: https://lkml.org/lkml/2013/4/4/639
> v4: https://lkml.org/lkml/2013/4/11/829
> 
> Since pagetable pages are used by the kernel, they cannot be offlined.
> As a result, they cannot be hot-remove.
> 
> This patch fix this problem with the following solution:
> 
>      1.   Introduce a new bootmem type LOCAL_NODE_DATAL, and register local
>           pagetable pages as LOCAL_NODE_DATAL by setting page->lru.next to
>           LOCAL_NODE_DATAL, just like we register SECTION_INFO pages.
> 
>      2.   Skip LOCAL_NODE_DATAL pages in offline/online procedures. When the
>           whole memory block they reside in is offlined, the kernel can
>           still access the pagetables.
>           (This changes the semantics of offline/online a little bit.)
> 
>      3.   Do not free LOCAL_NODE_DATAL pages to buddy system because they
>           were skipped when in offline/online procedures. The memory block
>           they reside in could have been offlined.
> 

s/LOCAL_NODE_DATAL/LOCAL_NODE_DATA

> Anyway, this problem should be fixed. Any better idea is welcome.
> 
> Change log:
> v1 -> v2:
>         patch2: As suggested by Wu Jianguo, define a macro to check if a page
>                 cantains local node data.
>         patch4: As suggested by Wu Jianguo, prevent freeing LOCAL_NODE_DATA
>                 pages in free_pagetable() instead of in put_page_bootmem().
> 
> Tang Chen (4):
>   bootmem, mem-hotplug: Register local pagetable pages with
>     LOCAL_NODE_DATA when freeing bootmem.
>   mem-hotplug: Skip LOCAL_NODE_DATA pages in memory offline procedure.
>   mem-hotplug: Skip LOCAL_NODE_DATA pages in memory online procedure.
>   mem-hotplug: Do not free LOCAL_NODE_DATA pages to buddy system in
>     hot-remove procedure.
> 
>  arch/x86/mm/init_64.c          |   10 +++++++-
>  include/linux/memblock.h       |   22 +++++++++++++++++
>  include/linux/memory_hotplug.h |   20 +++++++++++++--
>  mm/memblock.c                  |   52 ++++++++++++++++++++++++++++++++++++++++
>  mm/memory_hotplug.c            |   31 +++++++++++++++++++++++
>  mm/page_alloc.c                |   15 ++++++++++-
>  mm/page_isolation.c            |    5 ++++
>  7 files changed, 149 insertions(+), 6 deletions(-)
> 
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