> Hello.
>
> I would like to post patch set to free pages which is allocated by bootmem
> for memory-hotremove.
>
> 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 solved.
>
> 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
> offlined already and all pages must be isolated against
> page allocater. Kernel keeps it as is.
> 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 migrator will be able to check and skip
> memmap againt page isolation when page offline.
> Current page migration 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 set needs Badari-san's generic __remove_pages() support patch.
>
http://linux.derkeiler.com/Mailing-Lists/Kernel/2008-03/msg02881.html
>
> I think this patch set is not perfect. Because, some of section/node
> informations are smaller than one page, and bootmem allocator may
> mix other data. This patch is still trial.
> But I suppose this is good start for everyone to understand what is necessary.
>
> Please comments.
>
> Other Todo:
> - for SPARSEMEM_VMEMMAP.
> Freeing vmemmap's page is more diffcult than normal sparsemem.
> Because not only memmap's page, but also the pages like page table must
> be removed too. If removing section has pages for , then it must
> be migrated too. Relocatable page table is necessary.
>
> - compile with other config.
> This version is just for requesting comments.
> If this way is accepted, I'll check it.
> - Follow fix bootmem by Yinghai Lu-san.
> (This patch set is for 2.6.25-rc3-mm1 with Badari-san's patch yet.)
>
> Thanks.
>
