linux-kernel - Re: [PATCH] mm: cma: fix alignment requirements for contiguous regions

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Date:	Fri, 24 Aug 2012 18:46:34 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linaro-mm-sig@...ts.linaro.org
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] mm: cma: fix alignment requirements for contiguous regions

Marek Szyprowski <m.szyprowski@...sung.com> writes:
> Contiguous Memory Allocator requires each of its regions to be aligned
> in such a way that it is possible to change migration type for all
> pageblocks holding it and then isolate page of largest possible order from
> the buddy allocator (which is MAX_ORDER-1). This patch relaxes alignment
> requirements by one order, because MAX_ORDER alignment is not really
> needed.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> CC: Michal Nazarewicz <mina86@...a86.com>

Acked-by: Michal Nazarewicz <mina86@...a86.com>

> ---
>  drivers/base/dma-contiguous.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 78efb03..34d94c7 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -250,7 +250,7 @@ int __init dma_declare_contiguous(struct device *dev, unsigned long size,
>  		return -EINVAL;
>  
>  	/* Sanitise input arguments */
> -	alignment = PAGE_SIZE << max(MAX_ORDER, pageblock_order);
> +	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
>  	base = ALIGN(base, alignment);
>  	size = ALIGN(size, alignment);
>  	limit &= ~(alignment - 1);


-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--

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