• Yasunori Goto's avatar
    memory hotplug: register section/node id to free · 04753278
    Yasunori Goto authored
    This patch set is to free pages which is allocated by bootmem for
    memory-hotremove.  Some structures of memory management are allocated by
    bootmem.  ex) memmap, etc.
    To remove memory physically, some of them must be freed according to
    circumstance.  This patch set makes basis to free those pages, and free
    Basic my idea is using remain members of struct page to remember information
    of users of bootmem (section number or node id).  When the section is
    removing, kernel can confirm it.  By this information, some issues can be
      1) When the memmap of removing section is allocated on other
         section by bootmem, it should/can be free.
      2) When the memmap of removing section is allocated on the
         same section, it shouldn't be freed. Because the section has to be
         logical memory offlined already and all pages must be isolated against
         page allocater. If it is freed, page allocator may use it which will
         be removed physically soon.
      3) When removing section has other section's memmap,
         kernel will be able to show easily which section should be removed
         before it for user. (Not implemented yet)
      4) When the above case 2), the page isolation will be able to check and skip
         memmap's page when logical memory offline (offline_pages()).
         Current page isolation code fails in this case because this page is
         just reserved page and it can't distinguish this pages can be
         removed or not. But, it will be able to do by this patch.
         (Not implemented yet.)
      5) The node information like pgdat has similar issues. But, this
         will be able to be solved too by this.
         (Not implemented yet, but, remembering node id in the pages.)
    Fortunately, current bootmem allocator just keeps PageReserved flags,
    and doesn't use any other members of page struct. The users of
    bootmem doesn't use them too.
    This patch:
    This is to register information which is node or section's id.  Kernel can
    distinguish which node/section uses the pages allcated by bootmem.  This is
    basis for hot-remove sections or nodes.
    Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
    Cc: Badari Pulavarty <pbadari@us.ibm.com>
    Cc: Yinghai Lu <yhlu.kernel@gmail.com>
    Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
bootmem.c 14.1 KB