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SubjectRe: [PATCH 3/4] alloc_contig_pages() allocate big chunk memory using migration
On Fri, Nov 19, 2010 at 05:15:28PM +0900, KAMEZAWA Hiroyuki wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> Add an function to allocate contiguous memory larger than MAX_ORDER.
> The main difference between usual page allocator is that this uses
> memory offline technique (Isolate pages and migrate remaining pages.).
>
> I think this is not 100% solution because we can't avoid fragmentation,
> but we have kernelcore= boot option and can create MOVABLE zone. That
> helps us to allow allocate a contiguous range on demand.
>
> The new function is
>
> alloc_contig_pages(base, end, nr_pages, alignment)
>
> This function will allocate contiguous pages of nr_pages from the range
> [base, end). If [base, end) is bigger than nr_pages, some pfn which
> meats alignment will be allocated. If alignment is smaller than MAX_ORDER,
> it will be raised to be MAX_ORDER.
>
> __alloc_contig_pages() has much more arguments.
>
>
> Some drivers allocates contig pages by bootmem or hiding some memory
> from the kernel at boot. But if contig pages are necessary only in some
> situation, kernelcore= boot option and using page migration is a choice.
>
> Changelog: 2010-11-19
> - removed no_search
> - removed some drain_ functions because they are heavy.
> - check -ENOMEM case
>
> Changelog: 2010-10-26
> - support gfp_t
> - support zonelist/nodemask
> - support [base, end)
> - support alignment
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Minchan Kim <minchan.kim@gmail.com>

Trivial comment below.

> +EXPORT_SYMBOL_GPL(alloc_contig_pages);
> +
> +struct page *alloc_contig_pages_host(unsigned long nr_pages, int align_order)
> +{
> + return __alloc_contig_pages(0, max_pfn, nr_pages, align_order, -1,
> + GFP_KERNEL | __GFP_MOVABLE, NULL);
> +}

We need include #include <linux/bootmem.h> for using max_pfn.

--
Kind regards,
Minchan Kim


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