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SubjectRe: [PATCH] ARM: mm: Regarding section when dealing with meminfo
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.

>
> This patch guarantees that simple increasing the pointer to page
> descriptors does not exceed the boundary of a section.
>
> Signed-off-by: KyongHo Cho <pullip.cho@samsung.com>
> ---
> arch/arm/mm/init.c | 74 +++++++++++++++++++++++++++++++++++----------------
> 1 files changed, 51 insertions(+), 23 deletions(-)
>
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 57c4c5c..6ccecbe 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -93,24 +93,38 @@ void show_mem(void)
>
> pfn1 = bank_pfn_start(bank);
> pfn2 = bank_pfn_end(bank);
> -
> +#ifndef CONFIG_SPARSEMEM
> page = pfn_to_page(pfn1);
> end = pfn_to_page(pfn2 - 1) + 1;
> -
> +#else
> + pfn2--;
> do {
> - total++;
> - if (PageReserved(page))
> - reserved++;
> - else if (PageSwapCache(page))
> - cached++;
> - else if (PageSlab(page))
> - slab++;
> - else if (!page_count(page))
> - free++;
> - else
> - shared += page_count(page) - 1;
> - page++;
> - } while (page < end);
> + page = pfn_to_page(pfn1);
> + if (pfn_to_section_nr(pfn1) < pfn_to_section_nr(pfn2)) {
> + pfn1 += PAGES_PER_SECTION;
> + pfn1 &= PAGE_SECTION_MASK;
> + } else {
> + pfn1 = pfn2;
> + }
> + end = pfn_to_page(pfn1) + 1;
> +#endif
> + do {
> + total++;
> + if (PageReserved(page))
> + reserved++;
> + else if (PageSwapCache(page))
> + cached++;
> + else if (PageSlab(page))
> + slab++;
> + else if (!page_count(page))
> + free++;
> + else
> + shared += page_count(page) - 1;
> + page++;
> + } while (page < end);
> +#ifdef CONFIG_SPARSEMEM
> + } while (pfn1 < pfn2);
> +#endif
> }
>
> printk("%d pages of RAM\n", total);
> @@ -470,17 +484,31 @@ void __init mem_init(void)
>
> pfn1 = bank_pfn_start(bank);
> pfn2 = bank_pfn_end(bank);
> -
> +#ifndef CONFIG_SPARSEMEM
> page = pfn_to_page(pfn1);
> end = pfn_to_page(pfn2 - 1) + 1;
> -
> +#else
> + pfn2--;
> do {
> - if (PageReserved(page))
> - reserved_pages++;
> - else if (!page_count(page))
> - free_pages++;
> - page++;
> - } while (page < end);
> + page = pfn_to_page(pfn1);
> + if (pfn_to_section_nr(pfn1) < pfn_to_section_nr(pfn2)) {
> + pfn1 += PAGES_PER_SECTION;
> + pfn1 &= PAGE_SECTION_MASK;
> + } else {
> + pfn1 = pfn2;
> + }
> + end = pfn_to_page(pfn1) + 1;
> +#endif
> + do {
> + if (PageReserved(page))
> + reserved_pages++;
> + else if (!page_count(page))
> + free_pages++;
> + page++;
> + } while (page < end);
> +#ifdef CONFIG_SPARSEMEM
> + } while (pfn1 < pfn2);
> +#endif
> }

Hmm.. new ifndef magic makes code readability bad.
Couldn't we do it by simple pfn iterator not page and pfn_valid check?

>
> /*
> --
> 1.6.2.5
>
> --
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--
Kind regards,
Minchan Kim


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