Re: [PATCH -v2 05/13] x86, mm: Find early page table only one time

[Pekka Enberg <penberg@kernel.org>]

On Sun, Sep 2, 2012 at 10:46 AM, Yinghai Lu <yinghai@kernel.org> wrote:
> Should not do that in every calling of init_memory_mapping.
> Actually in early time, only need do once.
>
> Also move down early_memtest.
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>

The changelog is too terse for my liking. I think it could use some
more context on what the code is actually doing now and why the change
makes it better.

> ---
>  arch/x86/mm/init.c |   72 ++++++++++++++++++++++++++-------------------------
>  1 files changed, 37 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index cca9b7d..0ada295 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -37,7 +37,7 @@ struct map_range {
>
>  static int page_size_mask;
>
> -static void __init find_early_table_space(struct map_range *mr,
> +static void __init find_early_table_space(unsigned long begin,
>                                           unsigned long end)
>  {
>         unsigned long puds, pmds, ptes, tables, start = 0, good_end = end;
> @@ -64,8 +64,8 @@ static void __init find_early_table_space(struct map_range *mr,
>                 extra += PMD_SIZE;
>  #endif
>                 /* The first 2/4M doesn't use large pages. */
> -               if (mr->start < PMD_SIZE)
> -                       extra += mr->end - mr->start;
> +               if (begin < PMD_SIZE)
> +                       extra += (PMD_SIZE - begin) >> PAGE_SHIFT;
>
>                 ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
>         } else
> @@ -265,16 +265,6 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>         nr_range = 0;
>         nr_range = split_mem_range(mr, nr_range, start, end);
>
> -       /*
> -        * Find space for the kernel direct mapping tables.
> -        *
> -        * Later we should allocate these tables in the local node of the
> -        * memory mapped. Unfortunately this is done currently before the
> -        * nodes are discovered.
> -        */
> -       if (!after_bootmem)
> -               find_early_table_space(&mr[0], end);
> -
>         for (i = 0; i < nr_range; i++)
>                 ret = kernel_physical_mapping_init(mr[i].start, mr[i].end,
>                                                    mr[i].page_size_mask);
> @@ -287,6 +277,36 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>
>         __flush_tlb_all();
>
> +       return ret >> PAGE_SHIFT;
> +}
> +
> +void __init init_mem_mapping(void)
> +{
> +       probe_page_size_mask();
> +
> +       /*
> +        * Find space for the kernel direct mapping tables.
> +        *
> +        * Later we should allocate these tables in the local node of the
> +        * memory mapped. Unfortunately this is done currently before the
> +        * nodes are discovered.
> +        */
> +#ifdef CONFIG_X86_64
> +       find_early_table_space(0, max_pfn<<PAGE_SHIFT);
> +#else
> +       find_early_table_space(0, max_low_pfn<<PAGE_SHIFT);
> +#endif
> +       max_low_pfn_mapped = init_memory_mapping(0, max_low_pfn<<PAGE_SHIFT);
> +       max_pfn_mapped = max_low_pfn_mapped;
> +
> +#ifdef CONFIG_X86_64
> +       if (max_pfn > max_low_pfn) {
> +               max_pfn_mapped = init_memory_mapping(1UL<<32,
> +                                                    max_pfn<<PAGE_SHIFT);
> +               /* can we preseve max_low_pfn ?*/
> +               max_low_pfn = max_pfn;
> +       }
> +#endif
>         /*
>          * Reserve the kernel pagetable pages we used (pgt_buf_start -
>          * pgt_buf_end) and free the other ones (pgt_buf_end - pgt_buf_top)
> @@ -302,32 +322,14 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>          * RO all the pagetable pages, including the ones that are beyond
>          * pgt_buf_end at that time.
>          */
> -       if (!after_bootmem && pgt_buf_end > pgt_buf_start)
> +       if (pgt_buf_end > pgt_buf_start)
>                 x86_init.mapping.pagetable_reserve(PFN_PHYS(pgt_buf_start),
>                                 PFN_PHYS(pgt_buf_end));
>
> -       if (!after_bootmem)
> -               early_memtest(start, end);
> +       /* stop the wrong using */
> +       pgt_buf_top = 0;
>
> -       return ret >> PAGE_SHIFT;
> -}
> -
> -void __init init_mem_mapping(void)
> -{
> -       probe_page_size_mask();
> -
> -       /* max_pfn_mapped is updated here */
> -       max_low_pfn_mapped = init_memory_mapping(0, max_low_pfn<<PAGE_SHIFT);
> -       max_pfn_mapped = max_low_pfn_mapped;
> -
> -#ifdef CONFIG_X86_64
> -       if (max_pfn > max_low_pfn) {
> -               max_pfn_mapped = init_memory_mapping(1UL<<32,
> -                                                    max_pfn<<PAGE_SHIFT);
> -               /* can we preseve max_low_pfn ?*/
> -               max_low_pfn = max_pfn;
> -       }
> -#endif
> +       early_memtest(0, max_pfn_mapped << PAGE_SHIFT);
>  }
>
>  /*
> --
> 1.7.7
>
> --
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