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SubjectRe: [PATCH] mm: allocate usemap at first instead of mem_map in sparse_init
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On Wed, 2008-04-02 at 15:25 -0700, Yinghai Lu wrote:
> [PATCH] mm: allocate usemap at first instead of mem_map in sparse_init
> so try to allocate usemap at first altogether.
>
> Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index d3cb085..782ebe5 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -294,7 +294,7 @@ void __init sparse_init(void)
> unsigned long pnum;
> struct page *map;
> unsigned long *usemap;
> - struct page **section_map;
> + unsigned long **usemap_map;
> int size;
> int node;
>
> @@ -305,27 +305,31 @@ void __init sparse_init(void)
> * make next 2M slip to one more 2M later.
> * then in big system, the memmory will have a lot hole...
> * here try to allocate 2M pages continously.

Comments are x86-64 specific. On ppc its 16MB chunks :(

> + *
> + * powerpc hope to sparse_init_one_section right after each
> + * sparse_early_mem_map_alloc, so allocate usemap_map
> + * at first.
> */
> - size = sizeof(struct page *) * NR_MEM_SECTIONS;
> - section_map = alloc_bootmem(size);
> - if (!section_map)
> - panic("can not allocate section_map\n");
> + size = sizeof(unsigned long *) * NR_MEM_SECTIONS;
> + usemap_map = alloc_bootmem(size);
> + if (!usemap_map)
> + panic("can not allocate usemap_map\n");
>
> for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
> if (!present_section_nr(pnum))
> continue;
> - section_map[pnum] = sparse_early_mem_map_alloc(pnum);
> + usemap_map[pnum] = sparse_early_usemap_alloc(pnum);
> }
>
> for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
> if (!present_section_nr(pnum))
> continue;
>
> - map = section_map[pnum];
> + map = sparse_early_mem_map_alloc(pnum);
> if (!map)
> continue;
>
> - usemap = sparse_early_usemap_alloc(pnum);
> + usemap = usemap_map[pnum];
> if (!usemap)
> continue;

You may want to move this check before doing sparse_early_mem_map_alloc
(). We are also not handling errors properly (freeing up the unused
map or usemap) if we "continue". I know the original code is this way,
but you touched it last :)

>
> @@ -333,7 +337,7 @@ void __init sparse_init(void)
> usemap);
> }
>
> - free_bootmem(__pa(section_map), size);
> + free_bootmem(__pa(usemap_map), size);
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG

Tested and boots my machine fine.

Acked-by: Badari Pulavarty <pbadari@us.ibm.com>

Thanks,
Badari



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