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    SubjectRe: [PATCH] ARM: mm: Regarding section when dealing with meminfo
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    On Fri, Jan 21, 2011 at 2:44 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
    > Fix linux-arm-kernel address.
    >
    Thank you!
    Too late in the night:)

    > On Fri, Jan 21, 2011 at 2:43 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
    >> Restore Cced.
    >>
    >> On Fri, Jan 21, 2011 at 2:24 AM, KyongHo Cho <pullip.linux@gmail.com> wrote:
    >>> On Thu, Jan 20, 2011 at 11:28 PM, Minchan Kim <minchan.kim@gmail.com> wrote:
    >>>> On Thu, Jan 20, 2011 at 06:45:39PM +0900, KyongHo Cho wrote:
    >>>>> Sparsemem allows that a bank of memory spans over several adjacent
    >>>>> sections if the start address and the end address of the bank
    >>>>> belong to different sections.
    >>>>> When gathering statictics of physical memory in mem_init() and
    >>>>> show_mem(), this possiblity was not considered.
    >>>>
    >>>> Please write down the result if we doesn't consider this patch.
    >>>> I can understand what happens but for making good description and review,
    >>>> merging easily, it would be better to write down the result without
    >>>> the patch explicitly.
    >>>>
    >>> As we know that each section has its own memmap and
    >>> a contiguous chunk of physical memory that is represented by 'bank' in meminfo
    >>> can be larger than the size of a section.
    >>> "page++" in the current implementation can access invalid memory area.
    >>> The size of the section is 256 MiB in ARM and the number of banks in
    >>> meminfo is 8.
    >>> This means that the maximum size of the physical memory cannot be grow than 2GiB
    >>> to avoid this problem in the current implementation.
    >>> Thus we need to fix the calculation of the last page descriptor in
    >>> terms of sections.
    >>>
    >>> This patch determines the last page descriptor in a memmap with
    >>> min(last_pfn_of_bank, last_pfn_of_current_section)
    >>> If there remains physical memory not consumed, it calculates the last
    >>> page descriptor
    >>> with min(last_pfn_of_bank, last_pfn_of_next_section).
    >>>
    >>>>
    >>>> Hmm.. new ifndef magic makes code readability bad.
    >>>> Couldn't we do it by simple pfn iterator not page and pfn_valid check?
    >>>>
    >>> True.
    >>> We need to consider the implementation again.
    >>> I think the previous implementation gave the importance to the
    >>> efficiency but to the readability.
    >>>
    >>
    >> Please consider readability and consistency with other architectures
    >> if we can do. :)
    >> Thanks.
    >>
    >> --
    >> Kind regards,
    >> Minchan Kim
    >>
    >
    >
    >
    > --
    > Kind regards,
    > Minchan Kim
    >


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