linux-kernel - Re: [PATCH 3/4] alloc_contig_pages() allocate big chunk memory using migration

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Date:	Mon, 22 Nov 2010 00:25:56 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Bob Liu <lliubbo@...il.com>, fujita.tomonori@....ntt.co.jp,
	m.nazarewicz@...sung.com, pawel@...iak.com, andi.kleen@...el.com,
	felipe.contreras@...il.com,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>
Subject: Re: [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@...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@...fujitsu.com>
Acked-by: Minchan Kim <minchan.kim@...il.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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